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    <div class="os1">7.3 文本流QTextStream</div>
    <br>
    标准 C++ 有三个常见的输入输出流：iostream 处理命令行输入输出、fstream 处理文件输出输出、sstream
    处理内存字符串流的输入输出。通常将文本字符串转换成各种 C++ 变量的过程是输入，把内存中 C++ 变量表示成文本字符串的过程是输出。<br>
    Qt 提供了强大的文本流 QTextStream ，同时实现了三种 C++
    输入输出流的功能，并且还有功能增强，支持各种文本字符编码。QTextStream 一般用于操作各种编码格式的文本文件（QFile
    对象）或字符串（QString、QByteArray），也可以打开 stdin、stdout 和 stderr 命令行的输入输出，并自动处理本地化编码和
    Unicode 编码。<br>
    本节先将 QTextStream 类的内容分成四个小节来讲解，然后动手编写两个例子，将 QTextStream
    的三种用途全部实现一遍，最后附加一个技巧，就是图形界面程序和命令行输入输出的结合，虽然图形界面程序和命令行的协作很少，但多学一点也好。<br>
    <br>
    <div class="os2">7.3.1 QTextStream 构造函数和普通读写函数</div>
    <br>
    通常情况下 QTextStream 自己不会主动去打开一个文件，所以它的构造函数不接收文件名，而是接收 QFile 基类 QIODevice
    的指针，可以用 QFile 对象的指针构造 QTextStream ，但需要注意在构造 QTextStream 之前要调用 QFile 对象的
    open() 函数按需要的模式打开文件并检查是否正确打开。用于读写文件的 QTextStream 构造函数为：<br>
    <div class="code">&nbsp;&nbsp;&nbsp; QTextStream(QIODevice * device)</div>
    设备指针 device 需要提前用 open() 函数打开。<br>
    <br>
    对于文件设备，还有个不常用的构造函数：<br>
    <div class="code">&nbsp;&nbsp;&nbsp; QTextStream(FILE * fileHandle,
      QIODevice::OpenMode openMode = QIODevice::ReadWrite)</div>
    fileHandle 是文件句柄，因为 Qt 里面的文件一般都用 QFile
    处理，所以几乎不会用这个第二个函数处理文件。第二个构造函数的用途主要是和命令行的 stdin、stdout、stderr
    三个文件句柄协作，处理命令行的输入输出。<br>
    <br>
    以上两个构造函数第一个用于文件读写（类似 fstream），第二个一般用于命令行输入输出（类似 iostream），而 QTextStream
    第三个用途就是对内存字符串的格式化输入和输出（类似 sstream）。内存字符串输入输出，使用的构造函数为：<br>
    <div class="code">&nbsp;&nbsp;&nbsp; QTextStream(QString * string,
      QIODevice::OpenMode openMode = QIODevice::ReadWrite)</div>
    <div class="code">&nbsp;&nbsp;&nbsp; QTextStream(QByteArray * array,
      QIODevice::OpenMode openMode = QIODevice::ReadWrite)</div>
    <div class="code">&nbsp;&nbsp;&nbsp; QTextStream(const QByteArray &amp;
      array, QIODevice::OpenMode openMode = QIODevice::ReadOnly)</div>
    注意后两个构造函数，如果传递 QByteArray 对象给构造函数，那么这个 QByteArray 对象是只读的。<br>
    如果传递 QByteArray 指针给构造函数，那么默认是可读可写的。<br>
    <br>
    除了可以在构造函数指定文件设备或内存字符串，还可以在运行时修改：<br>
    <div class="code">void QTextStream::setDevice(QIODevice * device)</div>
    <div class="code">void QTextStream::setString(QString * string,
      QIODevice::OpenMode openMode = QIODevice::ReadWrite)</div>
    目前没有重新设置 QByteArray 的函数，只有修改文件设备和 QString 的函数。<br>
    <br>
    我们这里约定一下概念，无论 QTextStream 构造函数里是文件设备或内存字符串，本节后面都把 QTextStream 对象称为 文本流。<br>
    如果我们需要从文本流提取各种 C++ 基本数值类型，如 short、int、long、double ，这些读操作一般用 7.3.2 节的操作子和运算符
    &lt;&lt;、&gt;&gt;来实现，写入文本流时也一样。流操作子和运算符之外的读写函数就是本小节说的普通读写函数。<br>
    读取一整行文本的函数：<br>
    <div class="code">QString QTextStream::readLine(qint64 maxlen = 0)</div>
    QTextStream::readLine() 读取一行文本的时候，返回字符串末尾剔除了换行符（"\n"&nbsp; 或 "\r\n"），而上一节
    QIODevice 和 QFile 的 readLine() 函数返回字符串末尾带有一个 "\n" ，要注意区分。<br>
    如果要读取文本流中所有内容，可以用快捷函数：<br>
    <div class="code">QString QTextStream::readAll()</div>
    如果希望从文本流中读取指定长度的文本，可以用函数：<br>
    <div class="code">QString QTextStream::read(qint64 maxlen)</div>
    参数里是最多读取的字符数目，如果文本流里的数据不够，返回的字符串就是剩余的字符数。<br>
    <br>
    在使用 QFile 对象指针构造 QTextStream 的时候，一旦把 QFile 对象指针交给 QTextStream 之后，就不要再调用
    QFile 对象自己的读写函数了，因为 QTextStream 使用自己缓存的文件游标，底层 QFile 对象自己又进行读写之后，二者的文件游标很可能不
    一致，会造成读写的混乱。既然使用 QTextStream 读写文件，那就只用 QTextStream 的读写函数或输入输出运算符。<br>
    <br>
    QTextStream 的文件游标（其实应该叫文本流游标）可以用函数获取、移动，以及判断是否到达文件末尾：<br>
    <div class="code">qint64 QTextStream::pos() const&nbsp;&nbsp;&nbsp;
      //获取游标位置</div>
    <div class="code">bool QTextStream::seek(qint64 pos)//移动游标到 pos</div>
    <div class="code">bool QTextStream::atEnd() const&nbsp;&nbsp;&nbsp; //是否到达文
      本流末尾</div>
    <br>
    对于文本流的写入操作，QTextStream 压根没有 write() 函数，写入操作全部是通过输出运算符 &lt;&lt; 和流操作子实现的。<br>
    我们下面看看流操作子和 &lt;&lt;、&gt;&gt; 运算符。<br>
    <br>
    <div class="os2">7.3.2 QTextStream 流操作子和运算符</div>
    <br>
    绝大多数情况下，QTextStream 都是利用 &gt;&gt; 运算符进行输入，利用 &lt;&lt;
    运算符进行输出，与这两个运算符配合的有一大堆操作子，这些操作子和 iostream
    的操作子很类似，而且名字也几乎一样。流操作子一般用于控制输入输出的格式，大部分流操作子不带参数，Qt 提供额外提供了三个带参数的全局操作子，等会都列出
    来。<br>
    <br>
    QTextStream 支持所有 C++ 基本类型变量输入输出，并支持 Qt 自家的 QChar、QString、QByteArray，举例来说：<br>
    <div class="code">QTextStream &amp; QTextStream::operator&lt;&lt;(signed
      int i)</div>
    <div class="code">QTextStream &amp; QTextStream::operator&gt;&gt;(signed
      int &amp; i)</div>
    第一个是整型变量的输出运算符（或叫插入运算符）函数，第二个是整型变量的输入运算符（或叫提取运算符）函数。<br>
    QTextStream 在代码里面进行输入输出，就与标准 C++ 的 cin 和 cout 一样用就可以了。例如：<br>
    <div class="code"><span style=" color:#c0c0c0;">&nbsp;&nbsp;&nbsp; </span><span
        style=" color:#800080;">QString</span><span style=" color:#c0c0c0;"> </span><span
        style=" color:#000000;">strIn</span><span style=" color:#c0c0c0;"> </span><span
        style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
        style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span
        style=" color:#008000;">"100</span><span style=" color:#c0c0c0;">&nbsp;
      </span><span style=" color:#008000;">29.88"</span><span style=" color:#000000;">);</span>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800080;">QTextStream</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tsIn</span><span style=" color:#000000;">(&amp;</span><span
style=" color:#000000;">strIn</span><span style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">int</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">nNum</span><span style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">double</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">dblVal</span><span
style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//输入</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">tsIn</span><span
style=" color:#000000;">&gt;&gt;</span><span style=" color:#000000;">nNum</span><span
style=" color:#000000;">&gt;&gt;</span><span style=" color:#000000;">dblVal</span><span
style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//打印</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000080;">qDebug</span><span
style=" color:#000000;">()&lt;&lt;</span><span style=" color:#000000;">nNum</span><span
style=" color:#000000;">&lt;&lt;</span><span style=" color:#000000;">dblVal</span><span
style=" color:#000000;">;</span></pre>
    </div>
    这段代码执行后 nNum 就是数值 100， dblVal 就是浮点数 29.88 。qDebug()
    其实就是获取调试输出流的对象，然后打印了两个数值。<br>
    <br>
    QTextStream 里面重载的 &lt;&lt; 和 &gt;&gt; 运算符就不一个个列举了，讲一下关于字符串读取的三个：<br>
    <div class="code">QTextStream &amp; QTextStream::operator&gt;&gt;(QString
      &amp; str)</div>
    <div class="code">QTextStream &amp;
      QTextStream::operator&gt;&gt;(QByteArray &amp; array)</div>
    <div class="code">QTextStream &amp; QTextStream::operator&gt;&gt;(char * c)</div>
    QTextStream 对于字符串的读取，其实只读取一个单词，而不是一整行。比如如果文本流原始为 "Hello world, aha
    !"，如果用上面三个函数从头读取，那么读取的都只是第一个单词 "Hello" ，在源头的文件或内存字符串中，文本流中间都没有字符串终结符 '\0'，所以
    QTextStream 在输入时按照空白字符切割单词，每个单词算作一个小字符串返回。空白字符包括空格、制表符、换行符等等。<br>
    <br>
    另外当文本流用 &gt;&gt; 读取逐个字符到 QChar 或 char 变量里面时，可以用 <br>
    <div class="code">void QTextStream::skipWhiteSpace()</div>
    跳过空白字符，如果不跳过空白字符，那么 QChar 和 char 也会接收到空白字符，如空格、制表符、换行符等等。<br>
    <br>
    对于字符串的输出就没有上面那些问题了，因为输出时可以明确知道参数里的 QString 、QByteArray 、char * 是以 '\0' 结尾的，在
    '\0' 前面的字符串都会被写入到输出文本流中。<br>
    <br>
    输出文本流需要注意的是 QTextStream 有较大的输出缓冲区，如果用 stdout 或 stderr 构造 QTextStream
    对象打印输出，要常用 flush&nbsp; 或 endl 操作子函数清空缓存，及时显示输出：<br>
    <div class="code">tsOut&lt;&lt;flush;</div>
    <div class="code">tsOut&lt;&lt;endl;</div>
    flush 和 endl 的区别是 endl 会换行，flush 不换行。<br>
    <br>
    流的输入输出运算符用起来比较简单，下面重点看看控制格式的操作子，操作子本质都是函数，比如常用的换行 endl：<br>
    <div class="code">QTextStream &amp; endl(QTextStream &amp; stream)</div>
    <br>
    我们这里把 QTextStream 的操作子大致列举并解释一下：<br>
    ① 数值的进制和符号、小数点<br>
    <br>
    <table class="tabel">
      <tbody>
        <tr class="d1">
          <td style="width: 200px;" align="center"><b>操作子</b></td>
          <td align="center"><b> 描述</b></td>
        </tr>
        <tr>
          <td>bin</td>
          <td> 读写二进制整数，等同于 setIntegerBase(2). </td>
        </tr>
        <tr class="d1">
          <td>oct</td>
          <td> 读写八进制整数，等同于 setIntegerBase(8). </td>
        </tr>
        <tr>
          <td>dec</td>
          <td> 读写十进制整数，等同于 setIntegerBase(10). </td>
        </tr>
        <tr class="d1">
          <td>hex</td>
          <td> 读写十六进制整数，等同于 setIntegerBase(16). </td>
        </tr>
        <tr>
          <td>showbase</td>
          <td> 输出时显示数值进制前缀，比如 "0x" 、"0"、"0b"，等同于 setNumberFlags(numberFlags() |
            ShowBase). </td>
        </tr>
        <tr class="d1">
          <td>forcesign</td>
          <td> 强制显示正号（正数和0前面），等同于 setNumberFlags(numberFlags() | ForceSign). </td>
        </tr>
        <tr>
          <td>forcepoint</td>
          <td> 强制显示整数末尾的小数点，等同于 setNumberFlags(numberFlags() | ForcePoint). </td>
        </tr>
        <tr class="d1">
          <td>noshowbase</td>
          <td> 不显示进制的前缀，等同于 setNumberFlags(numberFlags() &amp; ~ShowBase). </td>
        </tr>
        <tr>
          <td>noforcesign</td>
          <td> 不强制显示正号，等同于 setNumberFlags(numberFlags() &amp; ~ForceSign). </td>
        </tr>
        <tr class="d1">
          <td>noforcepoint</td>
          <td> 不强制显示小数点，等同于 setNumberFlags(numberFlags() &amp; ~ForcePoint). </td>
        </tr>
        <tr>
          <td>uppercasebase</td>
          <td> 数值进制的前缀为大写，如 "0X" 、"0B"，等同于 setNumberFlags(numberFlags() |
            UppercaseBase). </td>
        </tr>
        <tr class="d1">
          <td>uppercasedigits</td>
          <td> 基数大于10进制的数值里面的字母大写，比如16进制的 "FE00"，
            等同于setNumberFlags(numberFlags() | UppercaseDigits). </td>
        </tr>
        <tr>
          <td>lowercasebase</td>
          <td> 数值进制的前缀小写，如 "0x" 、"0b"，等同于 setNumberFlags(numberFlags() &amp;
            ~UppercaseBase). </td>
        </tr>
        <tr class="d1">
          <td>lowercasedigits</td>
          <td> 基数大于10进制的数值里面的字母小写，比如16进制的 "fe00"， 等同于
            setNumberFlags(numberFlags() &amp; ~UppercaseDigits). </td>
        </tr>
      </tbody>
    </table>
    <br>
    ② 浮点数格式<br>
    <br>
    <table class="tabel">
      <tbody>
        <tr class="d1">
          <td style="width: 200px;" align="center"><b>操作子</b></td>
          <td align="center"><b> 描述</b></td>
        </tr>
        <tr>
          <td>fixed</td>
          <td> 以定点数显示实数（比如 float、double 类型），比如 1024.1234，等同于
            setRealNumberNotation(FixedNotation). </td>
        </tr>
        <tr class="d1">
          <td>scientific</td>
          <td> 以科学计数法显示实数，比如 1.0241234e3，等同于
            setRealNumberNotation(ScientificNotation). </td>
        </tr>
        <tr>
          <td>qSetRealNumberPrecision(int precision)</td>
          <td> 这是全局操作子，带一个整型参数，指定实数显示的精度位数，等同于
            QTextStream::setRealNumberPrecision(precision). </td>
        </tr>
      </tbody>
    </table>
    <br>
    qSetRealNumberPrecision(int) 会对后续所有实数变量输出都生效，直到被改变为止，实数精度默认是 6
    位，如果希望还原就设置精度为 6 。注意使用操作子 qSetRealNumberPrecision(int) 时最好一块明确指定使用 fixed 或者
    scientific，这样显示结果才是符合预期的小数位精度。<br>
    <br>
    ③ 域宽和对齐方式、填充字符<br>
    <br>
    <table class="tabel">
      <tbody>
        <tr class="d1">
          <td style="width: 200px;" align="center"><b>操作子</b></td>
          <td align="center"><b> 描述</b></td>
        </tr>
        <tr>
          <td>qSetFieldWidth(int width)</td>
          <td> 全局操作子，带一个整型参数，设定变量输出后的显示宽度，不足的用填充字符补齐（默认用空格补），等同于
            QTextStream::setFieldWidth(width). </td>
        </tr>
        <tr class="d1">
          <td>qSetPadChar(QChar ch)</td>
          <td> 全局操作子，带一个字符参数，如果设置的域宽比变量显示需要的宽度更宽，就用这个填充字符填补（默认是空格 ' '），等同于
            QTextStream::setPadChar(ch). </td>
        </tr>
        <tr>
          <td>left</td>
          <td> 设定域宽比变量显示需要的更宽时，变量显示时左对齐，右边空位补 PadChar， 等同于
            setFieldAlignment(AlignLeft). </td>
        </tr>
        <tr class="d1">
          <td>right</td>
          <td> 设定域宽比变量显示需要的更宽时，变量显示时右对齐，左边空位补 PadChar， 等同于
            setFieldAlignment(AlignRight). </td>
        </tr>
        <tr>
          <td>center</td>
          <td> 设定域宽比变量显示需要的更宽时，变量显示时居中对齐，两边空位补 PadChar， 等同于
            setFieldAlignment(AlignCenter). </td>
        </tr>
      </tbody>
    </table>
    <br>
    注意：qSetFieldWidth(int) 设置域宽之后，如果不重新设置，它就一直生效， 对后续所有变量输出都管用，包括 endl 都会补齐变为
    指定宽 度。 如果要还原成不设置域宽的状态，就调用操作子 qSetFieldWidth(0) 。 <br>
    qSetPadChar(QChar) 设置填充字符之后也是一直持续生效，直到被重新设置，如果还原成空格，就调用操作子
    qSetPadChar(QChar(0x20)) 。<br>
    <br>
    ④ 其他操作子<br>
    <br>
    <table class="tabel">
      <tbody>
        <tr class="d1">
          <td style="width: 200px;" align="center"><b>操作子</b></td>
          <td align="center"><b> 描述</b></td>
        </tr>
        <tr>
          <td>endl</td>
          <td> 添加换行符并清空输出缓存，把缓冲数据都写到输出文本流，等同于 stream &lt;&lt; '\n' &lt;&lt;
            flush; </td>
        </tr>
        <tr class="d1">
          <td>flush</td>
          <td> 清空输出缓冲区，把缓冲数据都写到输出文本流，等同于 QTextStream::flush() </td>
        </tr>
        <tr>
          <td>reset</td>
          <td> 把之前操作子或格式函数设定的格式全部重置，还原到流对象构建时的默认格式， 等同于 QTextStream::reset() </td>
        </tr>
        <tr class="d1">
          <td>ws</td>
          <td> 跳过输入文本流里的空白字符（包括空格、制表符、换行符等），直至遇到非空白字符， 等同于
            QTextStream::skipWhiteSpace() </td>
        </tr>
        <tr>
          <td>bom</td>
          <td> 除非确定是写入 Unicode 文本文件否则不要设置，如果要设置，必须在所有写入操作之前调用该操作子， 等同于
            setGenerateByteOrderMark(true). </td>
        </tr>
      </tbody>
    </table>
    <br>
    bom（Byte Order Mark）只用于 Unicode 编码的文本文件，如果不是写入 Unicode
    的字符编码格式（UTF-8、UTF-16、UTF-32）文本，就不要用 bom，后面的小节会讲到文本流和字符编码格式。<br>
    <br>
    <div class="os2">7.3.3 QTextStream 工作状态</div>
    <br>
    本小节说明一下文本流的工作状态，以输入文本流为例，源头文本为 "Hello world, aha !" ，我们如果执行：<br>
    <div class="code"><span style=" color:#c0c0c0;">&nbsp;&nbsp;&nbsp; </span><span
        style=" color:#008000;">//文本源</span>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800080;">QString</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strSrc</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">"Hello</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">world,</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">aha</span><span style=" color:#c0c0c0;"> </span><span style=" color:#008000;">!"</span><span
style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800080;">QTextStream</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tsIn</span><span style=" color:#000000;">(</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">&amp;</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strSrc</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//变量</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800080;">QString</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strTemp</span><span
style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">tsIn</span><span
style=" color:#000000;">&gt;&gt;</span><span style=" color:#000000;">strTemp</span><span
style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000080;">qDebug</span><span
style=" color:#000000;">()&lt;&lt;</span><span style=" color:#000000;">strTemp</span><span
style=" color:#000000;">;</span></pre>
    </div>
    这段代码会从文本流提取一个单词赋值给 strTemp ，这样的输入操作当然是对的。但如果强行从非数值字符串提取数值到整型或浮点数类型，那么会发生什么呢？<br>
    <div class="code"><span style=" color:#c0c0c0;">&nbsp;&nbsp;&nbsp; </span><span
        style=" color:#008000;">//文本源</span>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800080;">QString</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strSrc</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">"Hello</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">world,</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">aha</span><span style=" color:#c0c0c0;"> </span><span style=" color:#008000;">!"</span><span
style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800080;">QTextStream</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tsIn</span><span style=" color:#000000;">(</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">&amp;</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strSrc</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//变量</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">int</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">nNum</span><span style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">tsIn</span><span
style=" color:#000000;">&gt;&gt;</span><span style=" color:#000000;">nNum</span><span
style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000080;">qDebug</span><span
style=" color:#000000;">()&lt;&lt;</span><span style=" color:#000000;">nNum</span><span
style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000080;">qDebug</span><span
style=" color:#000000;">()&lt;&lt;</span><span style=" color:#000000;">tsIn</span><span
style=" color:#000000;">.</span><span style=" color:#000000;">status</span><span
style=" color:#000000;">();</span></pre>
    </div>
    strSrc 里面压根没有整型数值对应的字符串，上面代码执行之后 nNum 会被设置成默认的数值&nbsp; 0，而这时候 tsIn
    应该报错才对，输入流发生了错误，无法为整型数提供 nNum 提供数值。<br>
    文本流是通过状态变化来反映刚才的输入或输出操作有无错误发生，获取当前文本流的状态就是用函数：<br>
    <div class="code">Status QTextStream::status() const</div>
    枚举类型 Status 目前共有 4 个不同的枚举值：<br>
    <br>
    <table class="tabel">
      <tbody>
        <tr class="d1">
          <td style="width: 200px;" align="center"><b>Status 枚举常量</b></td>
          <td style="width: 200px;" align="center"><b>数值</b></td>
          <td align="center"><b> 描述</b></td>
        </tr>
        <tr>
          <td>QTextStream::Ok</td>
          <td> 0 </td>
          <td> 正常操作状态，没出错。 </td>
        </tr>
        <tr class="d1">
          <td>QTextStream::ReadPastEnd</td>
          <td> 1 </td>
          <td> 底层设备已到达末尾，比如文件末尾，无数据可读了。 </td>
        </tr>
        <tr>
          <td>QTextStream::ReadCorruptData</td>
          <td> 2 </td>
          <td> 读入了腐化数据，典型的就是文本源内容与目标变量类型不匹配。 </td>
        </tr>
        <tr class="d1">
          <td>QTextStream::WriteFailed</td>
          <td> 3 </td>
          <td> 无法向底层设备写入数据，比如文件是只读的。 </td>
        </tr>
      </tbody>
    </table>
    <br>
    对于上面示例的代码，文本源没有整型变量对应的字符串，当 tsIn 向 nNum 输入数据时，就会发生
    QTextStream::ReadCorruptData 错误，tsIn.status() 返回的数值就是 2 。<br>
    在进行文本流的输入输出时，如果出现莫名奇妙的错误，一定要注意检查文本流 QTextStream
    的状态，很可能发生内容字符串与变量类型不匹配，或者无法写入底层设备等。<br>
    <br>
    <span style="font-weight: bold; color: red;">编程时需要仔细考虑用户的输入和程序输出是否异常！</span><br>
    <br>
    对于错误的输入或输出应该如何处理呢？简单方法就是跳过错误的部分或用消息框提示，然后可以重新设置流的状态：<br>
    <div class="code">void QTextStream::setStatus(Status
      status)&nbsp;&nbsp;&nbsp; //把文本流设为指定状态</div>
    <div class="code">void QTextStream::resetStatus()&nbsp;&nbsp;&nbsp;
      //把状态重置为初始的 Ok 状态</div>
    <br>
    <div class="os2">7.3.4 QTextStream 与字符编码格式</div>
    <br>
    请读者回顾一下 3.1 节的字符编码格式，对于 Unix/Linux 系统，默认的本地化文本字符编码是 UTF-8，对于简体中文 Windows
    默认文本字符编码是 GBK，繁体中文 Windows 默认是 Big5 。QTextStream
    类是比较智能的，它可以自动检测文本字符的本地化编码，在输入时，它自动把本地化编码字符串转成 Qt 需要的类型，比如 QString 默认内码是
    UTF-16 ；在输出时，QTextStream 也会把 QString 变量的内码 UTF-16 转成本地化的字符串写入输出文本流。<br>
    <br>
    QTextStream 不仅能对文本文件的本地化编码自动处理，也能与 操作系统本地的命令行交互，在交互过程中也会自动转码。QTextStream
    还能自动检测 UTF-8、UTF-16、UTF-32 这些编码的文本，自动转为 Qt 默认的编码格式。使用 QTextStream
    与操作系统里的文本文件、命令行等打交道，就不需要操心文本编码的问题。<br>
    <br>
    但是如果真的要手动指定 QTextStream 输入流或输出流的编码格式，那也是可行的。如果要获取当前文本流的字符编码格式，使用函数：<br>
    <div class="code">QTextCodec * QTextStream::codec() const</div>
    设置文本字符编码格式，使用函数：<br>
    <div class="code">void QTextStream::setCodec(QTextCodec * codec)</div>
    QTextCodec 对象指针一般都是用 QTextCodec 类的静态函数获取：<br>
    <div class="code">QTextCodec * QTextCodec::codecForName(const char *
      name)&nbsp;&nbsp;&nbsp; //静态函数</div>
    <br>
    QTextStream 类为方便程序员设定文本的字符编码格式，提供了一个更方便的 setCodec() 函数：<br>
    <div class="code">void QTextStream::setCodec(const char * codecName)</div>
    这个 setCodec() 函数直接以编码的名称字符串为构造函数，内部自己调用 QTextCodec 类的静态函数获取文本字符编码器。<br>
    <br>
    一般 QTextStream 不需要手动设置字符编码格式，当然，程序员如果知道应该用什么样的字符编码输入输出，就可以自己改，比如下面示范的就是按照
    "UTF-8" 编码格式输出：<br>
    <div class="code"><span style=" color:#c0c0c0;">&nbsp;&nbsp;&nbsp; </span><span
        style=" color:#800080;">QString</span><span style=" color:#c0c0c0;"> </span><span
        style=" color:#000000;">strSrc</span><span style=" color:#c0c0c0;"> </span><span
        style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
        style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span
        style=" color:#008000;">"Hello</span><span style=" color:#c0c0c0;"> </span><span
        style=" color:#008000;">world,</span><span style=" color:#c0c0c0;"> </span><span
        style=" color:#008000;">aha</span><span style=" color:#c0c0c0;"> </span><span
        style=" color:#008000;">!"</span><span style=" color:#000000;">);</span>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//输出</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800080;">QFile</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">fileOut</span><span
style=" color:#000000;">(</span><span style=" color:#008000;">"test.txt"</span><span
style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">if</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">!</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">fileOut</span><span
style=" color:#000000;">.</span><span style=" font-style:italic; color:#000000;">open</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#800080;">QIODevice</span><span
style=" color:#000000;">::</span><span style=" color:#800080;">WriteOnly</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">)</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">)</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">{</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#808000;">return</span><span
style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">}</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800080;">QTextStream</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tsOut</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">&amp;</span><span
style=" color:#000000;">fileOut</span><span style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">tsOut</span><span
style=" color:#000000;">.</span><span style=" color:#000000;">setCodec</span><span
style=" color:#000000;">(</span><span style=" color:#008000;">"UTF-8"</span><span
style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">tsOut</span><span
style=" color:#000000;">&lt;&lt;</span><span style=" color:#000000;">strSrc</span><span
style=" color:#000000;">;</span></pre>
    </div>
    通常 UTF-8 格式不需要 bom，如果要为 UTF-16 或 UTF-32 编码的文本加 bom 头，一定要在所有的输出操作之前调用
    tsOut&lt;&lt;bom ;<br>
    <br>
    改变 QTextStream 的文本字符编码格式只需要一句代码而已，但是要根据实际需求来定，一般不需要自己设定字符编码格式。<br>
    <br>
    QTextStream 还提供了与世界各国本地语言习惯 QLocale 相关的函数 locale() 和 setLocale(const QLocale
    &amp; locale)，这个与各国的语言语种有关系，最好不要修改，用默认的即可，默认的 QLocale::C 不会影响数据输入输出。<br>
    <br>
    <div class="os2">7.3.5 读写文本文件示例</div>
    <br>
    本小节的例子主要实现读写自定义的文本格式，里面内容是这样的：<br>
    <div class="code">#姓名 岁数&nbsp; 体重<br>
      小明&nbsp; 18&nbsp; 50.5<br>
      小萌&nbsp; 19&nbsp; 55.8<br>
      小日&nbsp; 17&nbsp; 60.0<br>
      小月&nbsp; 16&nbsp; 55.1<br>
      小草&nbsp; 18&nbsp; 58.6</div>
    里面内容相当于是一个表格，第一行是井号打头的注释行，是预先定义好的三列表头。<br>
    然后从第二行开始是表格的数据，第一列是姓名，第二列是岁数，第三列是体重。每列数据之间用空格或者制表符分隔，每行的数据就用换行符分隔。我们下面开始编写示例
    程序，能够读写这样的文本文件。<br>
    <br>
    我们打开 QtCreator，新建一个 Qt Widgets Application 项目，在新建项目的向导里填写：<br>
    ①项目名称 tableedit，创建路径 D:\QtProjects\ch07，点击下一步；<br>
    ②套件选择里面选择全部套件，点击下一步；<br>
    ③基类选择 QWidget，点击下一步；<br>
    ④项目管理不修改，点击完成。<br>
    建好项目之后，先在项目文件夹里新建一个记事本文件，命名为 people.txt，把上面示范的文本内容保存到该文件里面，程序运行时会 用到。<br>
    <br>
    现在回到 QtCreator，打开窗体 widget.ui 文件，进入设计模式，把主窗体大小设置为 480 * 300，然后按照下图排布，拖入控件：<br>
    <center><img src="images/ch07/ch07-03-01.png" alt="ui" width="800"></center>
    上面控件从左边看是两大行：<br>
    第一大行：左边是 QListWidget 控件，对象名为
    listWidget，右边是一个垂直布局器，在垂直布局器里面有三个按钮和一个垂直弹簧条。竖排的第一个按钮，文本 "加载表格"，对象名
    pushButtonLoad，第二个按钮，文本 "保存表格"，对象名 pushButtonSave ，然后是垂直的弹簧条
    verticalSpacer，第三个按钮，文本 "删除行"，对象名 pushButtonDelRow 。<br>
    第一大行是按照水平布局器布局。<br>
    <br>
    第二大行：标签控件，文本 "姓名"，单行编辑器，对象名 lineEditName；<br>
    标签控件，文本 "岁数"，单行编辑器，对象名 lineEditAge；<br>
    标签控件，文本 "体重"，单行编辑器，对象名 lineEditWeight；<br>
    按钮控件，文本 "添加行"，对象名为 pushButtonAddRow。<br>
    第二大行也是按水平布局器排布。<br>
    <br>
    主窗体是以垂直布局器作为主布局。<br>
    <br>
    按照上面描述设置好界面和布局之后，首先分四次为四个按钮添加 clicked() 信号对应的槽函数：<br>
    <center><img src="images/ch07/ch07-03-02.png" alt="slot1"></center>
    四个按钮的用途比较明了，就是按钮文本显示的，上面两个按钮用于从文件加载表格和写入数据到文本文件；下面两个按钮用于从列表控件删除一行数据或者添加一行数据。<br>
    然后我们为列表控件 listWidget 添加 currentRowChanged(int) 信号对应的槽函数：<br>
    <center><img src="images/ch07/ch07-03-03.png" alt="slot2"></center>
    当用户在列表控件选中某行时，我们利用这个信号对应的槽函数，把该行的数据同步显示到三个单行编辑器里面，方便用户编辑数据，然后添加行或删除行。<br>
    <br>
    按上面描述添加好槽函数之后，我们保存界面文件，关闭界面文件，回到 QtCreator 代码编辑模式。<br>
    先来看看 widget.h 文件内容，这个头文件内容全是自动生成的，不需要修改：<br>
    <div class="code"><span style=" color:#000080;">#ifndef</span><span style=" color:#c0c0c0;">
      </span>WIDGET_H
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000080;">#define</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000080;">WIDGET_H</span></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000080;">#include</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">&lt;QWidget&gt;</span></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#808000;">namespace</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#800080;">Ui</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">{</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#808000;">class</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#800080;">Widget</span><span style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">}</span></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#808000;">class</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#800080;">Widget</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">:</span><span style=" color:#c0c0c0;"> </span><span style=" color:#808000;">public</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#800080;">QWidget</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">{</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000080;">Q_OBJECT</span></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#808000;">public</span><span style=" color:#000000;">:</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">explicit</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#800080;">Widget</span><span
style=" color:#000000;">(</span><span style=" color:#800080;">QWidget</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">*</span>parent<span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000080;">0</span><span style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">~</span><span style=" font-style:italic; color:#000000;">Widget</span><span
style=" color:#000000;">();</span></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#808000;">private</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#808000;">slots</span><span style=" color:#000000;">:</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">void</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">on_pushButtonLoad_clicked</span><span
style=" color:#000000;">();</span></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">void</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">on_pushButtonSave_clicked</span><span
style=" color:#000000;">();</span></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">void</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">on_pushButtonDelRow_clicked</span><span
style=" color:#000000;">();</span></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">void</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">on_pushButtonAddRow_clicked</span><span
style=" color:#000000;">();</span></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">void</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">on_listWidget_currentRowChanged</span><span
style=" color:#000000;">(</span><span style=" color:#808000;">int</span><span style=" color:#c0c0c0;"> </span>currentRow<span
style=" color:#000000;">);</span></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#808000;">private</span><span style=" color:#000000;">:</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800080;">Ui</span><span
style=" color:#000000;">::</span><span style=" color:#800080;">Widget</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">*</span><span style=" color:#800000;">ui</span><span
style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">};</span></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000080;">#endif</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">//</span><span style=" color:#c0c0c0;"> </span><span style=" color:#008000;">WIDGET_H</span></pre>
    </div>
    <br>
    然后我们打开源代码文件 widget.cpp，开始编写功能代码，首先编写头文件包含和构造函数的部分：<br>
    <div class="code"><span style=" color:#000080;">#include</span><span style=" color:#c0c0c0;">
      </span><span style=" color:#008000;">"widget.h"</span>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000080;">#include</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">"ui_widget.h"</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000080;">#include</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">&lt;QDebug&gt;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000080;">#include</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">&lt;QMessageBox&gt;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000080;">#include</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">&lt;QFileDialog&gt;</span><span style=" color:#c0c0c0;">      </span><span
style=" color:#008000;">//打开或保存文件对话框</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000080;">#include</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">&lt;QFile&gt;</span><span style=" color:#c0c0c0;">            </span><span
style=" color:#008000;">//文件类</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000080;">#include</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">&lt;QTextStream&gt;</span><span style=" color:#c0c0c0;">      </span><span
style=" color:#008000;">//文本流输入输出</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000080;">#include</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">&lt;QListWidgetItem&gt;</span><span style=" color:#c0c0c0;">  </span><span
style=" color:#008000;">//列表控件条目</span></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#800080;">Widget</span><span style=" color:#000000;">::</span><span
style=" color:#000000;">Widget</span><span style=" color:#000000;">(</span><span
style=" color:#800080;">QWidget</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">*</span><span style=" color:#000000;">parent</span><span
style=" color:#000000;">)</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">:</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800080;">QWidget</span><span
style=" color:#000000;">(</span><span style=" color:#000000;">parent</span><span
style=" color:#000000;">),</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800000;">ui</span><span
style=" color:#000000;">(</span><span style=" color:#808000;">new</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#800080;">Ui</span><span style=" color:#000000;">::</span><span style=" color:#800080;">Widget</span><span
style=" color:#000000;">)</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">{</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800000;">ui</span><span
style=" color:#000000;">-&gt;</span><span style=" color:#000000;">setupUi</span><span
style=" color:#000000;">(</span><span style=" color:#808000;">this</span><span style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//设置列表控件的选中模式，一次只能选一行</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800000;">ui</span><span
style=" color:#000000;">-&gt;</span><span style=" color:#800000;">listWidget</span><span
style=" color:#000000;">-&gt;</span><span style=" color:#000000;">setSelectionMode</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#800080;">QAbstractItemView</span><span
style=" color:#000000;">::</span><span style=" color:#800080;">SingleSelection</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">}</span></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#800080;">Widget</span><span style=" color:#000000;">::~</span><span
style=" font-style:italic; color:#000000;">Widget</span><span style=" color:#000000;">()</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">{</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">delete</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#800000;">ui</span><span style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">}</span></pre>
    </div>
    包含的 &lt;QFileDialog&gt;、&lt;QFile&gt; 是文件对话框和文件类，&lt;QTextStream&gt;
    是本节的文本流，&lt;QListWidgetItem&gt; 是列表控件条目，用于从列表条目提取信息。<br>
    <br>
    构造函数只添加了一句代码，就是设置列表控件的选中模式，每次只能选中一行，这样简化我们 "删除行" 按钮的操作，每次只处理一行。<br>
    <br>
    接下来是 "加载表格" 按钮对应的槽函数：<br>
    <div class="code"><span style=" color:#808000;">void</span><span style=" color:#c0c0c0;">
      </span><span style=" color:#800080;">Widget</span><span style=" color:#000000;">::</span><span
        style=" color:#000000;">on_pushButtonLoad_clicked</span><span style=" color:#000000;">()</span>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">{</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//获取打开文件名</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800080;">QString</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strFile</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#800080;">QFileDialog</span><span style=" color:#000000;">::</span><span
style=" color:#000000;">getOpenFileName</span><span style=" color:#000000;">(</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">                </span><span style=" color:#808000;">this</span><span
style=" color:#000000;">,</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">                </span><span style=" color:#000000;">tr</span><span
style=" color:#000000;">(</span><span style=" color:#008000;">"打开文件"</span><span
style=" color:#000000;">),</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">                </span><span style=" color:#000000;">tr</span><span
style=" color:#000000;">(</span><span style=" color:#008000;">"."</span><span style=" color:#000000;">),</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">                </span><span style=" color:#000000;">tr</span><span
style=" color:#000000;">(</span><span style=" color:#008000;">"Text</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">Files(*.txt);;All</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">files(*)"</span><span
style=" color:#000000;">)</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">                </span><span style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//判断文件名</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">if</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strFile</span><span
style=" color:#000000;">.</span><span style=" color:#000000;">isEmpty</span><span
style=" color:#000000;">()</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">)</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">{</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#808000;">return</span><span
style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">}</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//有文件名，定义文件对象并打开</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800080;">QFile</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">fileIn</span><span
style=" color:#000000;">(</span><span style=" color:#000000;">strFile</span><span
style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">if</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">!</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">fileIn</span><span
style=" color:#000000;">.</span><span style=" font-style:italic; color:#000000;">open</span><span
style=" color:#000000;">(</span><span style=" color:#800080;">QIODevice</span><span
style=" color:#000000;">::</span><span style=" color:#800080;">ReadOnly</span><span
style=" color:#000000;">)</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">)</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">{</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#800080;">QMessageBox</span><span
style=" color:#000000;">::</span><span style=" color:#000000;">warning</span><span
style=" color:#000000;">(</span><span style=" color:#808000;">this</span><span style=" color:#000000;">,</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span
style=" color:#008000;">"打开文件"</span><span style=" color:#000000;">),</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">                             </span><span style=" color:#000000;">tr</span><span
style=" color:#000000;">(</span><span style=" color:#008000;">"打开文件失败："</span><span
style=" color:#000000;">)</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">+</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">fileIn</span><span
style=" color:#000000;">.</span><span style=" color:#000000;">errorString</span><span
style=" color:#000000;">());</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#808000;">return</span><span
style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">}</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//文件已经正确打开，定义文本流</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800080;">QTextStream</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tsIn</span><span style=" color:#000000;">(&amp;</span><span
style=" color:#000000;">fileIn</span><span style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//表格的列数据类型</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800080;">QString</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strCurName</span><span
style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">int</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">nCurAge</span><span
style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">double</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">dblCurWeight</span><span
style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//先清空旧的列表</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800000;">ui</span><span
style=" color:#000000;">-&gt;</span><span style=" color:#800000;">listWidget</span><span
style=" color:#000000;">-&gt;</span><span style=" color:#000000;">clear</span><span
style=" color:#000000;">();</span></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//加载自定义的表格数据</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">while</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">!</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tsIn</span><span style=" color:#000000;">.</span><span
style=" color:#000000;">atEnd</span><span style=" color:#000000;">()</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">)</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">{</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#008000;">//提取打头的字符串</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">tsIn</span><span
style=" color:#000000;">&gt;&gt;</span><span style=" color:#000000;">strCurName</span><span
style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#008000;">//判断空行</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#808000;">if</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strCurName</span><span
style=" color:#000000;">.</span><span style=" color:#000000;">isEmpty</span><span
style=" color:#000000;">()</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">)</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">{</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">            </span><span style=" color:#000000;">tsIn</span><span
style=" color:#000000;">.</span><span style=" color:#000000;">skipWhiteSpace</span><span
style=" color:#000000;">();</span><span style=" color:#c0c0c0;">  </span><span style=" color:#008000;">//跳过空白</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">            </span><span style=" color:#808000;">continue</span><span
style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">}</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#008000;">//判断注释行</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#808000;">if</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strCurName</span><span
style=" color:#000000;">.</span><span style=" color:#000000;">startsWith</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#008000;">'#'</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">)</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">)</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">{</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">            </span><span style=" color:#008000;">//是注释行，跳过这一行</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">            </span><span style=" color:#000000;">tsIn</span><span
style=" color:#000000;">.</span><span style=" color:#000000;">readLine</span><span
style=" color:#000000;">();</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">            </span><span style=" color:#808000;">continue</span><span
style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">}</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#008000;">//现在</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">strCurName</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">是正常的人名</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#008000;">//提取后续的年龄、体重</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">tsIn</span><span
style=" color:#000000;">&gt;&gt;</span><span style=" color:#000000;">nCurAge</span><span
style=" color:#000000;">&gt;&gt;</span><span style=" color:#000000;">dblCurWeight</span><span
style=" color:#000000;">;</span></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#008000;">//原本可以用</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">arg</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">函数进行内存字符串格式化</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#008000;">//这里用文本流格式化输出到内存字符串里面</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#800080;">QString</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strOut</span><span
style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#800080;">QTextStream</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tsOut</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">&amp;</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strOut</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">tsOut</span><span
style=" color:#000000;">&lt;&lt;</span><span style=" color:#000000;">strCurName</span><span
style=" color:#000000;">&lt;&lt;</span><span style=" color:#008000;">"\t"</span><span
style=" color:#000000;">&lt;&lt;</span><span style=" color:#000000;">nCurAge</span><span
style=" color:#000000;">&lt;&lt;</span><span style=" color:#008000;">"\t"</span><span
style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#008000;">//定点数形式，精度为2，输出到内存字符串</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">tsOut</span><span
style=" color:#000000;">&lt;&lt;</span>fixed<span style=" color:#000000;">&lt;&lt;</span><span
style=" color:#000000;">qSetRealNumberPrecision</span><span style=" color:#000000;">(</span><span
style=" color:#000080;">2</span><span style=" color:#000000;">)&lt;&lt;</span><span
style=" color:#000000;">dblCurWeight</span><span style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#008000;">//内存中输出字符串填充好了，添加到列表控件</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#800000;">ui</span><span
style=" color:#000000;">-&gt;</span><span style=" color:#800000;">listWidget</span><span
style=" color:#000000;">-&gt;</span><span style=" color:#000000;">addItem</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strOut</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">}</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//提示加载完毕</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800080;">QMessageBox</span><span
style=" color:#000000;">::</span><span style=" color:#000000;">information</span><span
style=" color:#000000;">(</span><span style=" color:#808000;">this</span><span style=" color:#000000;">,</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span
style=" color:#008000;">"加载表格"</span><span style=" color:#000000;">),</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span
style=" color:#008000;">"加载自定义表格完毕。"</span><span style=" color:#000000;">));</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">}</span></pre>
    </div>
    这个槽函数前半部分代码是获取打开文件名 QFileDialog::getOpenFileName()，定义文件对象 fileIn
    并以只读模式打开文件，然 后根据文件对象指针 定义 输入文本流 tsIn 。<br>
    得到输入文本流 tsIn 之后，定义三个列的数据
    strCurName、nCurAge、dblCurWeight，用这三个变量循环加载文本流里面的行。加载数据前，先清空了列表控件的内容&nbsp;&nbsp;
    ui-&gt;listWidget-&gt;clear() 。<br>
    <br>
    函数后半部分代码就是用 while 循环加载数据：<br>
    <br>
    对于每行数据，先读取一个单词到 strCurName，如果单词为空，那么说明是空行，就跳过空白区域；<br>
    如果单词 strCurName 以井号打头，说明注释行，用 tsIn.readLine() 跳过注释行；<br>
    如果单词 strCurName 所在行不是空行也不是注释行，那么说明 strCurName 是姓名的列内容，读取该行后续的内容到两个变量 nCurAge
    和 dblCurWeight，这样就把文件中的一行读取到三个变量里面了。<br>
    <br>
    对于三个变量 strCurName 、nCurAge 、dblCurWeight，我们需要构造一个内存字符串 strOut，把三项数据都打印到
    strOut 里面，然后添加到列表控件显示。可以用 QString::arg() 函数实现格式化字符串，也可以用 QTextStream
    格式化内存字符串，我们这里使用 QTextStream 的方法，根据 strOut 构造输出流 tsOut，然后把变量打印到输出流，变量之间用制表符
    "\t" 分隔，对于浮点数 dblCurWeight 我们用定点数形式显示，显示精度为 2 。<br>
    <br>
    三个变量打印到输出流 tsOut，就等于都写入到内存字符串 strOut ，我们添加 strOut 到列表控件，就可以显示了。<br>
    <br>
    while 循环会一直执行到文件末尾，无数据可加载就结束循环，然后提示文件已经加载完毕。<br>
    这个函数展示了 QTextStream 的两个功能：加载已打开的文件（类似 fstream）；输出变量到内存字符串（类似 sstream）。<br>
    <br>
    然后我们来看看 "保存表格" 按钮对应的槽函数：<br>
    <div class="code"><span style=" color:#808000;">void</span><span style=" color:#c0c0c0;">
      </span><span style=" color:#800080;">Widget</span><span style=" color:#000000;">::</span><span
        style=" color:#000000;">on_pushButtonSave_clicked</span><span style=" color:#000000;">()</span>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">{</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//条目计数</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">int</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">nCount</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#800000;">ui</span><span style=" color:#000000;">-&gt;</span><span
style=" color:#800000;">listWidget</span><span style=" color:#000000;">-&gt;</span><span
style=" color:#000000;">count</span><span style=" color:#000000;">();</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">if</span><span
style=" color:#000000;">(</span><span style=" color:#000000;">nCount</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">&lt;</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000080;">1</span><span style=" color:#000000;">)</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">{</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#008000;">//没有数据</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#808000;">return</span><span
style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">}</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//获取保存的文件名</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800080;">QString</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strFileSave</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#800080;">QFileDialog</span><span style=" color:#000000;">::</span><span
style=" color:#000000;">getSaveFileName</span><span style=" color:#000000;">(</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">                </span><span style=" color:#808000;">this</span><span
style=" color:#000000;">,</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">                </span><span style=" color:#000000;">tr</span><span
style=" color:#000000;">(</span><span style=" color:#008000;">"保存文件"</span><span
style=" color:#000000;">),</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">                </span><span style=" color:#000000;">tr</span><span
style=" color:#000000;">(</span><span style=" color:#008000;">"."</span><span style=" color:#000000;">),</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">                </span><span style=" color:#000000;">tr</span><span
style=" color:#000000;">(</span><span style=" color:#008000;">"XLS</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">files(*.xls);;Text</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">Files(*.txt)"</span><span style=" color:#000000;">)</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">                </span><span style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">if</span><span
style=" color:#000000;">(</span><span style=" color:#000000;">strFileSave</span><span
style=" color:#000000;">.</span><span style=" color:#000000;">isEmpty</span><span
style=" color:#000000;">())</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">{</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#008000;">//文件名是空的</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#808000;">return</span><span
style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">}</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//打开输出文件</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800080;">QFile</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">fileOut</span><span
style=" color:#000000;">(</span><span style=" color:#000000;">strFileSave</span><span
style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">if</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">!</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">fileOut</span><span
style=" color:#000000;">.</span><span style=" font-style:italic; color:#000000;">open</span><span
style=" color:#000000;">(</span><span style=" color:#800080;">QIODevice</span><span
style=" color:#000000;">::</span><span style=" color:#800080;">WriteOnly</span><span
style=" color:#000000;">))</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">{</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#800080;">QMessageBox</span><span
style=" color:#000000;">::</span><span style=" color:#000000;">warning</span><span
style=" color:#000000;">(</span><span style=" color:#808000;">this</span><span style=" color:#000000;">,</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span
style=" color:#008000;">"保存文件"</span><span style=" color:#000000;">),</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">                             </span><span style=" color:#000000;">tr</span><span
style=" color:#000000;">(</span><span style=" color:#008000;">"打开保存文件失败："</span><span
style=" color:#000000;">)</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">+</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">fileOut</span><span
style=" color:#000000;">.</span><span style=" color:#000000;">errorString</span><span
style=" color:#000000;">());</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#808000;">return</span><span
style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">}</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//定义输出文本流</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800080;">QTextStream</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tsOut</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">&amp;</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">fileOut</span><span
style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//先打印一行表头</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">tsOut</span><span
style=" color:#000000;">&lt;&lt;</span><span style=" color:#000000;">tr</span><span
style=" color:#000000;">(</span><span style=" color:#008000;">"#姓名\t岁数\t体重"</span><span
style=" color:#000000;">)&lt;&lt;</span>endl<span style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//从列表提取信息</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">for</span><span
style=" color:#000000;">(</span><span style=" color:#808000;">int</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">i</span><span style=" color:#000000;">=</span><span style=" color:#000080;">0</span><span
style=" color:#000000;">;</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">i</span><span
style=" color:#000000;">&lt;</span><span style=" color:#000000;">nCount</span><span
style=" color:#000000;">;</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">i</span><span
style=" color:#000000;">++)</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">{</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#800080;">QString</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strCurAll</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#800000;">ui</span><span style=" color:#000000;">-&gt;</span><span
style=" color:#800000;">listWidget</span><span style=" color:#000000;">-&gt;</span><span
style=" color:#000000;">item</span><span style=" color:#000000;">(</span><span style=" color:#000000;">i</span><span
style=" color:#000000;">)-&gt;</span><span style=" color:#000000;">text</span><span
style=" color:#000000;">();</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">tsOut</span><span
style=" color:#000000;">&lt;&lt;</span><span style=" color:#000000;">strCurAll</span><span
style=" color:#000000;">&lt;&lt;</span>endl<span style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">}</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//提示保存完毕</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800080;">QMessageBox</span><span
style=" color:#000000;">::</span><span style=" color:#000000;">information</span><span
style=" color:#000000;">(</span><span style=" color:#808000;">this</span><span style=" color:#000000;">,</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span
style=" color:#008000;">"保存文件"</span><span style=" color:#000000;">),</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span
style=" color:#008000;">"保存表格文件成功。"</span><span style=" color:#000000;">));</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">}</span></pre>
    </div>
    这个槽函数先获取列表控件条目的计数，如果没数据就不需要保存。<br>
    如果有数据，就获取要保存的文件名，定义文件对象 fileOut，打开文件；<br>
    然后根据已经打开的文件对象 fileOut 指针定义输出文本流 tsOut。<br>
    <br>
    定义好输出文本流 tsOut 之后，先输出一行井号打头的表头信息；<br>
    然后循环输出列表控件的每一行文本到输出流。<br>
    将列表控件所有行输出到文件之后，提示保存成功信息。<br>
    <br>
    这里没有将从列表控件的每行文本提取
    姓名、岁数、体重三个变量，因为列表控件的每一行格式都是我们之前设计好的，都是符合自定义的表格文本规律，不需要再抽取数据，再把数据变成字符串，没必要倒来倒
    去。<br>
    <br>
    程序的输出永远比输入简单，因为输入可能有各种错误格式的信息，而输出时只要自己定义好了格式就行。<br>
    <br>
    这里教大家一个小技巧，在获取保存文件名时，我们默认的扩展名是 *.xls 。Excel 程序生成的 xls 文件我们不能打开，因为真正的 xls
    文件很复杂。但如果我们把记事本文件扩展名改为 xls，然后里面的每列用 "\t" 字符分隔，每行就用换行符，然后生成的文本文件，Excel
    程序是可以打开的，并且能正常识别表格。以后我们如果需要输出数据为 Excel 表格，就可以用这种假的 xls 文件，本质是文本文件，只要列用制表符
    "\t" ，行尾用普通换行符，那么 Excel 就能自动识别为表格。<br>
    <br>
    接下来是 "删除行" 按钮对应的槽函数的代码：<br>
    <div class="code"><span style=" color:#808000;">void</span><span style=" color:#c0c0c0;">
      </span><span style=" color:#800080;">Widget</span><span style=" color:#000000;">::</span><span
        style=" color:#000000;">on_pushButtonDelRow_clicked</span><span style=" color:#000000;">()</span>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">{</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//选取当前选中的行</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">int</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">nCurIndex</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#800000;">ui</span><span style=" color:#000000;">-&gt;</span><span
style=" color:#800000;">listWidget</span><span style=" color:#000000;">-&gt;</span><span
style=" color:#000000;">currentRow</span><span style=" color:#000000;">();</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">if</span><span
style=" color:#000000;">(</span><span style=" color:#000000;">nCurIndex</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">&lt;</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000080;">0</span><span style=" color:#000000;">)</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">{</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#008000;">//没有选中合法行</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#808000;">return</span><span
style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">}</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">else</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">{</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#008000;">//删除行</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#800000;">ui</span><span
style=" color:#000000;">-&gt;</span><span style=" color:#800000;">listWidget</span><span
style=" color:#000000;">-&gt;</span><span style=" color:#000000;">takeItem</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">nCurIndex</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">}</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">}</span></pre>
    </div>
    这个槽函数很简单，先获取当前选中的行，如果行的序号合法，就删除该行。列表控件删除行的函数为 takeItem() ，这个函数名比较特殊，不是 del*
    也不是 remove * 之类的名字。<br>
    <br>
    接下来是 "添加行" 按钮对应的槽函数代码：<br>
    <div class="code"><span style=" color:#808000;">void</span><span style=" color:#c0c0c0;">
      </span><span style=" color:#800080;">Widget</span><span style=" color:#000000;">::</span><span
        style=" color:#000000;">on_pushButtonAddRow_clicked</span><span style=" color:#000000;">()</span>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">{</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800080;">QString</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strName</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#800000;">ui</span><span style=" color:#000000;">-&gt;</span><span
style=" color:#800000;">lineEditName</span><span style=" color:#000000;">-&gt;</span><span
style=" color:#000000;">text</span><span style=" color:#000000;">().</span><span
style=" color:#000000;">trimmed</span><span style=" color:#000000;">();</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800080;">QString</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strAge</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#800000;">ui</span><span style=" color:#000000;">-&gt;</span><span
style=" color:#800000;">lineEditAge</span><span style=" color:#000000;">-&gt;</span><span
style=" color:#000000;">text</span><span style=" color:#000000;">().</span><span
style=" color:#000000;">trimmed</span><span style=" color:#000000;">();</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800080;">QString</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strWeight</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#800000;">ui</span><span style=" color:#000000;">-&gt;</span><span
style=" color:#800000;">lineEditWeight</span><span style=" color:#000000;">-&gt;</span><span
style=" color:#000000;">text</span><span style=" color:#000000;">().</span><span
style=" color:#000000;">trimmed</span><span style=" color:#000000;">();</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//判断是否为空</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">if</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strName</span><span
style=" color:#000000;">.</span><span style=" color:#000000;">isEmpty</span><span
style=" color:#000000;">()</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">||</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strAge</span><span
style=" color:#000000;">.</span><span style=" color:#000000;">isEmpty</span><span
style=" color:#000000;">()</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">||</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strWeight</span><span
style=" color:#000000;">.</span><span style=" color:#000000;">isEmpty</span><span
style=" color:#000000;">()</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">)</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">{</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#800080;">QMessageBox</span><span
style=" color:#000000;">::</span><span style=" color:#000000;">warning</span><span
style=" color:#000000;">(</span><span style=" color:#808000;">this</span><span style=" color:#000000;">,</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span
style=" color:#008000;">"添加行"</span><span style=" color:#000000;">),</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span
style=" color:#008000;">"请先填好三项数据再添加！"</span><span style=" color:#000000;">));</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#808000;">return</span><span
style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">}</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">int</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">nAge</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strAge</span><span
style=" color:#000000;">.</span><span style=" color:#000000;">toInt</span><span
style=" color:#000000;">();</span><span style=" color:#c0c0c0;">  </span><span style=" color:#008000;">//年龄</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">double</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">dblWeight</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">strWeight</span><span style=" color:#000000;">.</span><span
style=" color:#000000;">toDouble</span><span style=" color:#000000;">();</span><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//体重</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//判断年龄体重是否正确</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">if</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">(</span><span
style=" color:#000000;">nAge</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">&lt;</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000080;">0</span><span style=" color:#000000;">)</span><span
style=" color:#c0c0c0;">  </span><span style=" color:#000000;">||</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">(</span><span style=" color:#000000;">nAge</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">&gt;</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000080;">600</span><span
style=" color:#000000;">)</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">)</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">{</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#800080;">QMessageBox</span><span
style=" color:#000000;">::</span><span style=" color:#000000;">warning</span><span
style=" color:#000000;">(</span><span style=" color:#808000;">this</span><span style=" color:#000000;">,</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span
style=" color:#008000;">"添加行"</span><span style=" color:#000000;">),</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span
style=" color:#008000;">"年龄不能是负数或超过600！"</span><span style=" color:#000000;">));</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#808000;">return</span><span
style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">}</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">if</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">dblWeight</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">&lt;</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000080;">0.1</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">)</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">{</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#800080;">QMessageBox</span><span
style=" color:#000000;">::</span><span style=" color:#000000;">warning</span><span
style=" color:#000000;">(</span><span style=" color:#808000;">this</span><span style=" color:#000000;">,</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span
style=" color:#008000;">"添加行"</span><span style=" color:#000000;">),</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span
style=" color:#008000;">"重量不能低于</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">0.1</span><span style=" color:#c0c0c0;"> </span><span style=" color:#008000;">kg</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">！"</span><span style=" color:#000000;">));</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#808000;">return</span><span
style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">}</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//添加正确的数据，这里使用</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">arg</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">函数实现格式化字符串</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//无论用</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">arg</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">函数还是</span><span style=" color:#c0c0c0;"> </span><span style=" color:#008000;">QTextStream</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">都可以实现一样的效果</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800080;">QString</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strCurAll</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span style=" color:#008000;">"%1\t%2\t%3"</span><span
style=" color:#000000;">).</span><span style=" color:#000000;">arg</span><span style=" color:#000000;">(</span><span
style=" color:#000000;">strName</span><span style=" color:#000000;">)</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">            </span><span style=" color:#000000;">.</span><span
style=" color:#000000;">arg</span><span style=" color:#000000;">(</span><span style=" color:#000000;">nAge</span><span
style=" color:#000000;">)</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">            </span><span style=" color:#000000;">.</span><span
style=" color:#000000;">arg</span><span style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">dblWeight</span><span style=" color:#000000;">,</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000080;">0</span><span style=" color:#000000;">,</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">'f'</span><span style=" color:#000000;">,</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000080;">2</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800000;">ui</span><span
style=" color:#000000;">-&gt;</span><span style=" color:#800000;">listWidget</span><span
style=" color:#000000;">-&gt;</span><span style=" color:#000000;">addItem</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strCurAll</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">}</span></pre>
    </div>
    在添加行的时候，先获取三个单行编辑器的内容，如果单行编辑器内容为空就不处理。<br>
    然后我们把年龄字符串转为整型数，体重字符串转为浮点数类型。<br>
    判断年龄范围 0 到 600 ，判断体重必须有 0.1 kg，这里只是简单做一下输入数据的验证。<br>
    验证数据之后，我们用 QString 类的 arg 函数实现了格式化字符串，这三个 arg 函数效果和
    on_pushButtonLoad_clicked() 里面的输出文本流 tsOut 功能类似，都是把三个变量转为一个内存字符串，添加到列表控件。<br>
    <br>
    对于多个变量转为内存字符串，无论用 QTextStream 还是 QString::arg() 函数都可以，看程序员的喜好。<br>
    如果从内存字符串提取多个数值变量，那么毫无疑问是用 QTextStream 方便，因为 QTextStream
    自动分隔单词，自动转换为目标数值类型。QString 的 to***() 函数只能转换为一个变量，没法同时转为多个变量。<br>
    <br>
    最后一个函数就是列表控件选中的行变化时执行的槽函数：<br>
    <div class="code"><span style=" color:#008000;">//选中的行变化时，把当前选中行的数据显示到下方编辑器里
        面</span>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#808000;">void</span><span style=" color:#c0c0c0;"> </span><span style=" color:#800080;">Widget</span><span
style=" color:#000000;">::</span><span style=" color:#000000;">on_listWidget_currentRowChanged</span><span
style=" color:#000000;">(</span><span style=" color:#808000;">int</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">currentRow</span><span style=" color:#000000;">)</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">{</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">if</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">currentRow</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">&lt;</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000080;">0</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">)</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">{</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#008000;">//非法的行号不处理</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#808000;">return</span><span
style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">}</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//正常行号，读取行文本</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800080;">QString</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strCurAll</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#800000;">ui</span><span style=" color:#000000;">-&gt;</span><span
style=" color:#800000;">listWidget</span><span style=" color:#000000;">-&gt;</span><span
style=" color:#000000;">item</span><span style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">currentRow</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">)-&gt;</span><span style=" color:#000000;">text</span><span
style=" color:#000000;">();</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//根据字符串构造输入流</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800080;">QTextStream</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tsLine</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">&amp;</span><span
style=" color:#000000;">strCurAll</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//三项数据</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800080;">QString</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strName</span><span
style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">int</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">nAge</span><span style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">double</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">dblWeight</span><span
style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//从当前行文本提取三项数据</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">tsLine</span><span
style=" color:#000000;">&gt;&gt;</span><span style=" color:#000000;">strName</span><span
style=" color:#000000;">&gt;&gt;</span><span style=" color:#000000;">nAge</span><span
style=" color:#000000;">&gt;&gt;</span><span style=" color:#000000;">dblWeight</span><span
style=" color:#000000;">;</span></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//显示到三个编辑器</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800000;">ui</span><span
style=" color:#000000;">-&gt;</span><span style=" color:#800000;">lineEditName</span><span
style=" color:#000000;">-&gt;</span><span style=" color:#000000;">setText</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strName</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800000;">ui</span><span
style=" color:#000000;">-&gt;</span><span style=" color:#800000;">lineEditAge</span><span
style=" color:#000000;">-&gt;</span><span style=" color:#000000;">setText</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tr</span><span
style=" color:#000000;">(</span><span style=" color:#008000;">"%1"</span><span style=" color:#000000;">).</span><span
style=" color:#000000;">arg</span><span style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">nAge</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">)</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800000;">ui</span><span
style=" color:#000000;">-&gt;</span><span style=" color:#800000;">lineEditWeight</span><span
style=" color:#000000;">-&gt;</span><span style=" color:#000000;">setText</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tr</span><span
style=" color:#000000;">(</span><span style=" color:#008000;">"%1"</span><span style=" color:#000000;">).</span><span
style=" color:#000000;">arg</span><span style=" color:#000000;">(</span><span style=" color:#000000;">dblWeight</span><span
style=" color:#000000;">)</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">}</span></pre>
    </div>
    这个函数先判断参数里的当前行序号 currentRow ，如果行号不合法就不处理。<br>
    对于合法行号，提取当前的文本字符串 strCurAll ，这个字符串里面其实同时有三个变量对应的字符串，从内存字符串同时提取三个变量，用
    QTextStream 实现更方便。<br>
    我们根据 strCurAll 指针构造输入文本流 tsLine，然后直接用 &gt;&gt; 运算符提取三个变量就行了。<br>
    得到三个变量 strName 、nAge 、dblWeight 之后，把它们显示到相应的单行编辑器。<br>
    <br>
    可能有读者会觉得上面把变量和内存字符串倒来倒去有点重复操作，做无用功，是不是无用功不要紧。这个例子主要展示的就是如何用 QTextStream
    读写文件和 做内存字符串的格式化输入输出，把 QTextStream 的用法学会是主要目的。<br>
    <br>
    以上就是这个例子的代码，我们现在生成并运行例子看看效果，加载我们之前放好的 people.txt：<br>
    <center><img src="images/ch07/ch07-03-04.png" alt="run"></center>
    其他按钮功能读者自行测试一下，这里不截图了。这个例子展示了 QTextStream 的两个主要功能，读写文本文件（类似
    fstream），内存字符串的格式化输入输出（类似 sstream），还剩下一个在命令行输入输出（类似 iostream）的功能，作为下面的例子。<br>
    <br>
    <div class="os2">7.3.6 命令行输入输出示例</div>
    <br>
    我们之前一直用 QtCreator 新建图形界面的程序，现在我们新建一个 Qt 命令行程序，展示 QTextStream 的第三种用途。我们重新打开
    QtCreator，点击 "文件" --&gt; "新建文件或项目"，在新建对话框里，左边选择 "Application"，中间选择 "Qt
    控制台应用"，如下图所示：<br>
    <center><img src="images/ch07/ch07-03-05.png" alt="new1" width="800"></center>
    然后点击右下角的 Choose 按钮，进入下面界面：<br>
    <center><img src="images/ch07/ch07-03-06.png" alt="new2"></center>
    项目名称设置为 console，创建路径为 D:\QtProjects\ch07，点击 "下一步"，进入如下界面：<br>
    <center><img src="images/ch07/ch07-03-07.png" alt="new3"></center>
    选中所有的套件，点击 "下一步"，进入下面界面：
    <center><img src="images/ch07/ch07-03-08.png" alt="new4"></center>
    点击 "完成" 按钮，这样新的 console 控制台程序就建好了。<br>
    Qt 控制台项目很简单，只有 console.pro 和 main.cpp 是源代码文件，我们可以看看控制台项目 pro 文件内容：<br>
    <div class="code"><span style=" color:#008000;">#-------------------------------------------------</span>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#008000;">#</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#008000;">#</span><span style=" color:#c0c0c0;"> </span><span style=" color:#008000;">Project</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">created</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">by</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">QtCreator</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">2015-12-02T15:29:43</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#008000;">#</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#008000;">#-------------------------------------------------</span></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#800080;">QT</span><span style=" color:#c0c0c0;">       </span>+=<span
style=" color:#c0c0c0;"> </span>core</pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#800080;">QT</span><span style=" color:#c0c0c0;">       </span>-=<span
style=" color:#c0c0c0;"> </span>gui</pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#800080;">TARGET</span><span style=" color:#c0c0c0;"> </span>=<span
style=" color:#c0c0c0;"> </span>console</pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#800080;">CONFIG</span><span style=" color:#c0c0c0;">   </span>+=<span
style=" color:#c0c0c0;"> </span>console</pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#800080;">CONFIG</span><span style=" color:#c0c0c0;">   </span>-=<span
style=" color:#c0c0c0;"> </span>app_bundle</pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#800080;">TEMPLATE</span><span style=" color:#c0c0c0;"> </span>=<span
style=" color:#c0c0c0;"> </span>app</pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#800080;">SOURCES</span><span style=" color:#c0c0c0;"> </span>+=<span
style=" color:#c0c0c0;"> </span>main.cpp</pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
    </div>
    里面使用的模块只有 core，不使用 gui 模块。CONFIG 相关的行是项目类型的配置代码，<br>
    <div class="code"> CONFIG&nbsp;&nbsp; += console</div>
    就是明确指定使用命令行。<br>
    <div class="code"> CONFIG&nbsp;&nbsp; -= app_bundle</div>
    是指不使用 app_bundle ，这个 app_bundle (Puts the executable into a
    bundle)是苹果操作系统里的应用配置，对本例子没影响。<br>
    <br>
    QtCreator 新建的控制台项目默认只有一个 main.cpp ，因为不涉及图形界面，里面的内容很简单：<br>
    <div class="code"><span style=" color:#000080;">#include</span><span style=" color:#c0c0c0;">
      </span><span style=" color:#008000;">&lt;QCoreApplication&gt;</span>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#808000;">int</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">main</span><span
style=" color:#000000;">(</span><span style=" color:#808000;">int</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">argc</span><span style=" color:#000000;">,</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#808000;">char</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">*</span><span
style=" color:#000000;">argv</span><span style=" color:#000000;">[])</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">{</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800080;">QCoreApplication</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">a</span><span style=" color:#000000;">(</span><span
style=" color:#000000;">argc</span><span style=" color:#000000;">,</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">argv</span><span style=" color:#000000;">);</span></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">return</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">a</span><span style=" color:#000000;">.</span><span
style=" color:#000000;">exec</span><span style=" color:#000000;">();</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">}</span></pre>
    </div>
    QCoreApplication 是最基本的应用程序类型，对象 a 代表 Qt 控制台程序自己，main() 函数里没有其他代码。<br>
    <br>
    我们这个例子内容也比较简单，就是编写 main.cpp 文件里面的代码，首先是添加头文件包含和一个前置的函数声明：<br>
    <div class="code"><span style=" color:#000080;">#include</span><span style=" color:#c0c0c0;">
      </span><span style=" color:#008000;">&lt;QCoreApplication&gt;</span>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000080;">#include</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">&lt;QTextStream&gt;</span></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#008000;">//函数声明，根据不同功能代码实现输入输出功能</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#808000;">void</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">Funcs</span><span
style=" color:#000000;">(</span><span style=" color:#808000;">int</span><span style=" color:#c0c0c0;"> </span>nCode<span
style=" color:#000000;">,</span><span style=" color:#c0c0c0;"> </span><span style=" color:#800080;">QTextStream</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">&amp;</span>tsIn<span
style=" color:#000000;">,</span><span style=" color:#c0c0c0;"> </span><span style=" color:#800080;">QTextStream</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">&amp;</span>tsOut<span
style=" color:#000000;">);</span></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
    </div>
    Func() 函数接收一个功能代号 nCode，根据代号的不同，实现不同的功能，tsIn 是输入流（类似 cin），tsOut 是输出流（类似
    cout）。根据功能代码，从输入流 tsIn 提取不同类型的数值，然后打印对应的信息到输出流 tsOut ，原理就是这么简单。<br>
    <br>
    接下来看看修改之后的 main() 函数代码：<br>
    <div class="code"><span style=" color:#808000;">int</span><span style=" color:#c0c0c0;">
      </span><span style=" color:#000000;">main</span><span style=" color:#000000;">(</span><span
        style=" color:#808000;">int</span><span style=" color:#c0c0c0;"> </span><span
        style=" color:#000000;">argc</span><span style=" color:#000000;">,</span><span
        style=" color:#c0c0c0;"> </span><span style=" color:#808000;">char</span><span
        style=" color:#c0c0c0;"> </span><span style=" color:#000000;">*</span><span
        style=" color:#000000;">argv</span><span style=" color:#000000;">[])</span>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">{</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800080;">QCoreApplication</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">a</span><span style=" color:#000000;">(</span><span
style=" color:#000000;">argc</span><span style=" color:#000000;">,</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">argv</span><span style=" color:#000000;">);</span></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800080;">QTextStream</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tsIn</span><span style=" color:#000000;">(</span><span
style=" color:#000080;">stdin</span><span style=" color:#000000;">);</span><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//类似</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">cin</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800080;">QTextStream</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tsOut</span><span
style=" color:#000000;">(</span><span style=" color:#000080;">stdout</span><span
style=" color:#000000;">);</span><span style=" color:#c0c0c0;">  </span><span style=" color:#008000;">//类似</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">cout</span></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">while</span><span
style=" color:#000000;">(</span><span style=" color:#808000;">true</span><span style=" color:#000000;">)</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">{</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#008000;">//显示程序功能</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#800080;">QString</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strFuns</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">a</span><span style=" color:#000000;">.</span><span style=" color:#000000;">tr</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#008000;">"功能代码：\n"</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">                                </span><span style=" color:#008000;">"1.</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">输入整型数\n"</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">                                </span><span style=" color:#008000;">"2.</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">输入浮点数\n"</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">                                </span><span style=" color:#008000;">"3.</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">输入单词\n"</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">                                </span><span style=" color:#008000;">"4.</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">输入整行句子\n"</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">                                </span><span style=" color:#008000;">"9.</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">退出程序\n"</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">                                </span><span style=" color:#008000;">"请输入功能代码：</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">"</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">                                </span><span style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#008000;">//显示输出时一定要带上</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">&lt;&lt;flush</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">或者</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">&lt;&lt;endl</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">tsOut</span><span
style=" color:#000000;">&lt;&lt;</span><span style=" color:#000000;">strFuns</span><span
style=" color:#000000;">&lt;&lt;</span>flush<span style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#008000;">//获取用户输入功能代码</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#808000;">int</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">nCode</span><span
style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">tsIn</span><span
style=" color:#000000;">&gt;&gt;</span><span style=" color:#000000;">nCode</span><span
style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#808000;">if</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000080;">9</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">==</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">nCode</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">)</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">{</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">            </span><span style=" color:#000000;">tsOut</span><span
style=" color:#000000;">&lt;&lt;</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">a</span><span style=" color:#000000;">.</span><span style=" color:#000000;">tr</span><span
style=" color:#000000;">(</span><span style=" color:#008000;">"程序结束。"</span><span
style=" color:#000000;">)&lt;&lt;</span>endl<span style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">            </span><span style=" color:#008000;">//结束</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">            </span><span style=" color:#808000;">return</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000080;">0</span><span style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">}</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#808000;">else</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">{</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">            </span><span style=" color:#000000;">Funcs</span><span
style=" color:#000000;">(</span><span style=" color:#000000;">nCode</span><span
style=" color:#000000;">,</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tsIn</span><span
style=" color:#000000;">,</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tsOut</span><span
style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">}</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">}</span></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">return</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">a</span><span style=" color:#000000;">.</span><span
style=" color:#000000;">exec</span><span style=" color:#000000;">();</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">}</span></pre>
    </div>
    main() 函数开头的地方，stdin 就是命令行标准输入设备的文件句柄，stdout 就是标准输出设备的文件句柄，我们根据 stdin 和
    stdout 分别构造输入流 tsIn 和输出流 tsOut ，在命令行进行输入输出直接使用这两个 QTextStream
    对象即可，就是这么简单的两句。<br>
    <br>
    需要注意的是 tsOut 输出流，QTextStream 对象默认有较大的输出缓冲区，如果希望及时地显示输出消息，那需要在输出变量或文本时，加上操作子
    &lt;&lt;flush 或者 &lt;&lt;endl ，保证清空 tsOut 内部输出缓存，立即在命令行显示消息。<br>
    <br>
    在定义好 tsIn 和 tsOut 之后，是一个 while 循环，条件一直为真。<br>
    while 循环里的代码是先打印一条提示消息 strFuns ，告知用户可以输入哪些功能代码。<br>
    然后使用 tsIn 从输入流提取一个数值给 nCode ，判断 nCode 数值：<br>
    如果 nCode 为 9 ，就结束程序；<br>
    否则调用 Funcs() 函数，让 Funcs() 函数根据不同功能代码进行后续输入输出操作。<br>
    <br>
    现在我们来看看这个功能函数：<br>
    <div class="code"><span style=" color:#008000;">//功能函数定义</span>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#808000;">void</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">Funcs</span><span
style=" color:#000000;">(</span><span style=" color:#808000;">int</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">nCode</span><span style=" color:#000000;">,</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#800080;">QTextStream</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">&amp;</span><span
style=" color:#000000;">tsIn</span><span style=" color:#000000;">,</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#800080;">QTextStream</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">&amp;</span><span style=" color:#000000;">tsOut</span><span
style=" color:#000000;">)</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">{</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">tsOut</span><span
style=" color:#000000;">&lt;&lt;</span>endl<span style=" color:#000000;">;</span><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//开始时换行</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800080;">QString</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strOut</span><span
style=" color:#000000;">;</span><span style=" color:#c0c0c0;"> </span><span style=" color:#008000;">//打印字符串</span></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800080;">QString</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strIn</span><span
style=" color:#000000;">;</span><span style=" color:#c0c0c0;">  </span><span style=" color:#008000;">//接收单词和整行字符串</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">int</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">nNum</span><span style=" color:#000000;">;</span><span
style=" color:#c0c0c0;">           </span><span style=" color:#008000;">//接收整数</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">double</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">dblValue</span><span
style=" color:#000000;">;</span><span style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//接收浮点数</span></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">switch</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">(</span><span style=" color:#000000;">nCode</span><span
style=" color:#000000;">)</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">{</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">case</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000080;">1</span><span style=" color:#000000;">:</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">strOut</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000080;">qApp</span><span style=" color:#000000;">-&gt;</span><span
style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span style=" color:#008000;">"请输入整数：</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">"</span><span style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">tsOut</span><span
style=" color:#000000;">&lt;&lt;</span><span style=" color:#000000;">strOut</span><span
style=" color:#000000;">&lt;&lt;</span>flush<span style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">tsIn</span><span
style=" color:#000000;">&gt;&gt;</span><span style=" color:#000000;">nNum</span><span
style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#008000;">//显示</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">strOut</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000080;">qApp</span><span style=" color:#000000;">-&gt;</span><span
style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span style=" color:#008000;">"您刚输入的是：%1"</span><span
style=" color:#000000;">).</span><span style=" color:#000000;">arg</span><span style=" color:#000000;">(</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">nNum</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">tsOut</span><span
style=" color:#000000;">&lt;&lt;</span><span style=" color:#000000;">strOut</span><span
style=" color:#000000;">&lt;&lt;</span>endl<span style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#808000;">break</span><span
style=" color:#000000;">;</span></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">case</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000080;">2</span><span style=" color:#000000;">:</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">strOut</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000080;">qApp</span><span style=" color:#000000;">-&gt;</span><span
style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span style=" color:#008000;">"请输入浮点数：</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">"</span><span style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">tsOut</span><span
style=" color:#000000;">&lt;&lt;</span><span style=" color:#000000;">strOut</span><span
style=" color:#000000;">&lt;&lt;</span>flush<span style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">tsIn</span><span
style=" color:#000000;">&gt;&gt;</span><span style=" color:#000000;">dblValue</span><span
style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#008000;">//显示</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">strOut</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000080;">qApp</span><span style=" color:#000000;">-&gt;</span><span
style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span style=" color:#008000;">"您刚输入的是：%1"</span><span
style=" color:#000000;">).</span><span style=" color:#000000;">arg</span><span style=" color:#000000;">(</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">dblValue</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">tsOut</span><span
style=" color:#000000;">&lt;&lt;</span><span style=" color:#000000;">strOut</span><span
style=" color:#000000;">&lt;&lt;</span>endl<span style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#808000;">break</span><span
style=" color:#000000;">;</span></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">case</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000080;">3</span><span style=" color:#000000;">:</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">strOut</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000080;">qApp</span><span style=" color:#000000;">-&gt;</span><span
style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span style=" color:#008000;">"请输入一个单词：</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">"</span><span style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">tsOut</span><span
style=" color:#000000;">&lt;&lt;</span><span style=" color:#000000;">strOut</span><span
style=" color:#000000;">&lt;&lt;</span>flush<span style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">tsIn</span><span
style=" color:#000000;">&gt;&gt;</span><span style=" color:#000000;">strIn</span><span
style=" color:#000000;">;</span><span style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//读取空白分隔的一个单词</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#008000;">//显示</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">strOut</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000080;">qApp</span><span style=" color:#000000;">-&gt;</span><span
style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span style=" color:#008000;">"您刚输入的是：</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">%1"</span><span style=" color:#000000;">).</span><span
style=" color:#000000;">arg</span><span style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">strIn</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">tsOut</span><span
style=" color:#000000;">&lt;&lt;</span><span style=" color:#000000;">strOut</span><span
style=" color:#000000;">&lt;&lt;</span>endl<span style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#808000;">break</span><span
style=" color:#000000;">;</span></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">case</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000080;">4</span><span style=" color:#000000;">:</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">strOut</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000080;">qApp</span><span style=" color:#000000;">-&gt;</span><span
style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span style=" color:#008000;">"请输入一行字符串：</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">"</span><span style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">tsOut</span><span
style=" color:#000000;">&lt;&lt;</span><span style=" color:#000000;">strOut</span><span
style=" color:#000000;">&lt;&lt;</span>flush<span style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#008000;">//跳过用户输入功能代码时敲的回车键字符</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">tsIn</span><span
style=" color:#000000;">.</span><span style=" color:#000000;">skipWhiteSpace</span><span
style=" color:#000000;">();</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">strIn</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">tsIn</span><span style=" color:#000000;">.</span><span style=" color:#000000;">readLine</span><span
style=" color:#000000;">();</span><span style=" color:#c0c0c0;">    </span><span
style=" color:#008000;">//读取一行</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#008000;">//显示</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">strOut</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000080;">qApp</span><span style=" color:#000000;">-&gt;</span><span
style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span style=" color:#008000;">"您刚输入的是：</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">%1"</span><span style=" color:#000000;">).</span><span
style=" color:#000000;">arg</span><span style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">strIn</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">tsOut</span><span
style=" color:#000000;">&lt;&lt;</span><span style=" color:#000000;">strOut</span><span
style=" color:#000000;">&lt;&lt;</span>endl<span style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#808000;">break</span><span
style=" color:#000000;">;</span></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">default</span><span
style=" color:#000000;">:</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">strOut</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000080;">qApp</span><span style=" color:#000000;">-&gt;</span><span
style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span style=" color:#008000;">"未知功能代码</span><span
style=" color:#c0c0c0;">  </span><span style=" color:#008000;">%1</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">，不处理。"</span><span style=" color:#000000;">).</span><span
style=" color:#000000;">arg</span><span style=" color:#000000;">(</span><span style=" color:#000000;">nCode</span><span
style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">tsOut</span><span
style=" color:#000000;">&lt;&lt;</span><span style=" color:#000000;">strOut</span><span
style=" color:#000000;">&lt;&lt;</span>endl<span style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#808000;">break</span><span
style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">}</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//结束时再换一行</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">tsOut</span><span
style=" color:#000000;">&lt;&lt;</span>endl<span style=" color:#000000;">;</span></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">/**判断一下输入流的状态**/</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">if</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tsIn</span><span
style=" color:#000000;">.</span><span style=" color:#000000;">status</span><span
style=" color:#000000;">()</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">!=</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#800080;">QTextStream</span><span
style=" color:#000000;">::</span><span style=" color:#800080;">Ok</span><span style=" color:#000000;">)</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">{</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#008000;">//有可能出现用户输入错误，把错误的输入数据跳过去</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">tsIn</span><span
style=" color:#000000;">.</span><span style=" color:#000000;">readLine</span><span
style=" color:#000000;">();</span><span style=" color:#c0c0c0;">    </span><span
style=" color:#008000;">//跳过一行</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">tsIn</span><span
style=" color:#000000;">.</span><span style=" color:#000000;">resetStatus</span><span
style=" color:#000000;">();</span><span style=" color:#c0c0c0;"> </span><span style=" color:#008000;">//重置状态</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">}</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">}</span></pre>
    </div>
    Funcs()&nbsp; 代码主要就是一大段 switch-case 代码，如果 nCode 为 1，就提示用户输入一个整数，然后从 tsIn
    输入流提取一个数值给 nNum，然后构造 strOut 字符串，打印回显消息。<br>
    当 nCode 为 2、3、4 时，代码也是差不多的，只是接收的数据类型稍有差异。<br>
    <br>
    nCode 为 4 的时候，case 段落代码比其他情况多一行：tsIn.skipWhiteSpace();<br>
    这是因为当用户之前输入功能代码 '4' 的时候，会按一下回车键，这个回车键字符还在输入流里面，所以先要把这个回车键字符跳过去，再提取后面非空白的一行字符
    串。<br>
    <br>
    如果用户输入了未知的功能代码，那么打印提示信息，告知用户没法处理。<br>
    <br>
    在 Funcs() 函数末尾有一小段非常重要的排错代码，如果用户在前面过程输入了不合法的数据，比如把英文字母当作整数或浮点数输入，那么 tsIn
    的状态会变成 QTextStream::ReadCorruptData&nbsp; 状态。在这种情况下，输入流 tsIn
    里面腐化的数据，比如一堆英文字母，还会留在缓冲区，而且文本流的游标会卡在这段英文字母前面，一直无法移动，整个文本流会卡死在这。<br>
    <br>
    如果不使用 tsIn.readLine() 跳过一行腐化数据，那么 Funcs() 返回之后 ，main()&nbsp; 函数里的 while
    会一直持续循环打印错误信息，程序就失控了，用户就无法再操作。Func()&nbsp; 函数末尾有这段状态判断和跳过腐化数据代码，就保证程序不会因为错误的
    输入而一直失控。<br>
    <br>
    整个示例程序的代码就是上面那些，注意打印字符串是一定要用 tr() 函数封装或者转成 QString 变量打印，因为 QTextStream
    会对输入输出做本地化转码，使用 QString 类型保证字符串的输入输出不乱码。<br>
    Funcs() 函数里面调用 tr() 函数的方式是 qApp-&gt;tr()&nbsp; ，这里的 qApp 是 Qt
    程序默认定义的全局宏，代表应用程序对象自身指针，就是 main() 函数里的那个对象 a 的全局指针。QCoreApplication
    类内部也有静态函数 tr() ，与其他所有窗口和控件类的 tr() 函数是一样使用的。<br>
    <br>
    我们生成并运行一下示例程序看看，功能代码输入 3，本来程序提示输入单词，我们输入一整句： Hello world !<br>
    看到效果如下：<br>
    <center><img src="images/ch07/ch07-03-09.png" alt="run"></center>
    在输入一句 "Hello World !" 之后按回车，因为代码<br>
    <div class="code">
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">case</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000080;">3</span><span style=" color:#000000;">:</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">strOut</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000080;">qApp</span><span style=" color:#000000;">-&gt;</span><span
style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span style=" color:#008000;">"请输入一个单词：</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">"</span><span style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">tsOut</span><span
style=" color:#000000;">&lt;&lt;</span><span style=" color:#000000;">strOut</span><span
style=" color:#000000;">&lt;&lt;</span>flush<span style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">tsIn</span><span
style=" color:#000000;">&gt;&gt;</span><span style=" color:#000000;">strIn</span><span
style=" color:#000000;">;</span><span style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//读取空白分隔的一个单词</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#008000;">//显示</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">strOut</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000080;">qApp</span><span style=" color:#000000;">-&gt;</span><span
style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span style=" color:#008000;">"您刚输入的是：</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">%1"</span><span style=" color:#000000;">).</span><span
style=" color:#000000;">arg</span><span style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">strIn</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#000000;">tsOut</span><span
style=" color:#000000;">&lt;&lt;</span><span style=" color:#000000;">strOut</span><span
style=" color:#000000;">&lt;&lt;</span>endl<span style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span><span style=" color:#808000;">break</span><span
style=" color:#000000;">;</span></pre>
    </div>
    只会提取一个单词到&nbsp; strIn 里面，strIn 就等于 "Hello" ，后面的 "World !" 还在输入流里，没有提取。<br>
    然后回到 while 循环，这时候 while 循环开头打印了关于功能代码的提示信息，<br>
    程序会自动从输入流 "World !" 抽取一个整型数值给 nCode ，但输入流没有整型数对应的字符串，出现腐化数据输入的状态，nCode
    会被自动设置为 0，所以命令行出现了 "未知功能代码 0，不处理" 的信息。<br>
    之后在 Func()&nbsp; 函数末尾会对错误的输入流状态进行判断，并跳过错误的输入行，就把腐化数据 "World !"&nbsp;
    跳过去，接下来就是功能正常的 while 循环了。<br>
    <br>
    如果 Func() 末尾不判断输入流状态，不跳过一行腐化数据，那么程序输入就会卡死在 "World !" ，while
    就会不断打印错误信息，直到强制结束进程为止。<br>
    <br>
    即使是最简单的命令行程序，涉及到用户输入也要特别小心，因为非正常的输入信息容易导致无法预料的程序错误。程序员在编写代码时一定要注意检查用户的异常输入，异
    常输入处理不当，轻则程序崩溃，重则留下严重漏洞，为黑客留下可乘之机，所以要特别注意程序的输入检查。<br>
    <br>
    <div class="os2">7.3.7 附加技巧：图形程序和命令行输入输出协作</div>
    <br>
    一般情况下，使用图形界面就没必要使用命令行进行输入输出，因为有丰富的控件来接受输入和显示输出信息。图形界面的程序很少从命令行接收输入或打印输出，但是为了
    以防万一，这里教大家一个小技巧，可以让图形界面程序同时使用命令行的输入输出，虽然暂时不知道有什么用，就当一个附加技巧吧。<br>
    这个示例首先按照正常的图形界面程序创建项目，然后向 pro 文件添加一行代码，再修改项目的运行配置，就能实现我们预期的效果。下面开始这个示范过程。<br>
    <br>
    我们重新打开 QtCreator，新建一个 Qt Widgets Application 项目，在新建项目的向导里填写：<br>
    ①项目名称 guicui，创建路径 D:\QtProjects\ch07，点击下一步；<br>
    ②套件选择里面选择全部套件，点击下一步；<br>
    ③基类选择 QWidget，点击下一步；<br>
    ④项目管理不修改，点击完成。<br>
    <br>
    在 QtCreator 代码编辑模式，我们打开 guicui.pro 文件，向其中添加一句代码：<br>
    <div class="code"><span style=" color:#008000;">#-------------------------------------------------</span>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#008000;">#</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#008000;">#</span><span style=" color:#c0c0c0;"> </span><span style=" color:#008000;">Project</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">created</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">by</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">QtCreator</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">2015-12-04T17:00:52</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#008000;">#</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#008000;">#-------------------------------------------------</span></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#800080;">QT</span><span style=" color:#c0c0c0;">       </span>+=<span
style=" color:#c0c0c0;"> </span>core<span style=" color:#c0c0c0;"> </span>gui</pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;">greaterThan(<span
style=" color:#800080;">QT_MAJOR_VERSION</span>,<span style=" color:#c0c0c0;"> </span>4):<span
style=" color:#c0c0c0;"> </span><span style=" color:#800080;">QT</span><span style=" color:#c0c0c0;"> </span>+=<span
style=" color:#c0c0c0;"> </span>widgets</pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#800080;">TARGET</span><span style=" color:#c0c0c0;"> </span>=<span
style=" color:#c0c0c0;"> </span>guicui</pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#800080;">TEMPLATE</span><span style=" color:#c0c0c0;"> </span>=<span
style=" color:#c0c0c0;"> </span>app</pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#800080;">SOURCES</span><span style=" color:#c0c0c0;"> </span>+=<span
style=" color:#c0c0c0;"> </span>main.cpp\</pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">        </span>widget.cpp</pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#800080;">HEADERS</span><span style=" color:#c0c0c0;">  </span>+=<span
style=" color:#c0c0c0;"> </span>widget.h</pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#800080;">FORMS</span><span style=" color:#c0c0c0;">    </span>+=<span
style=" color:#c0c0c0;"> </span>widget.ui</pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#800080;">CONFIG</span><span style=" color:#c0c0c0;">   </span>+=<span
style=" color:#c0c0c0;"> </span>console</pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
    </div>
    最后一句&nbsp; CONFIG&nbsp;&nbsp; += console，就是新增的，必须在 pro 文件里加这一句，才能正常使用
    stdin、stdout 和 stderr 在命令行里进行输入输出。<br>
    <br>
    保存 pro 文件，关闭 pro 文件，然后我们点击 QtCreator 左侧的 "项目" 按钮，进入项目配置界面：<br>
    <center><img src="images/ch07/ch07-03-10.png" alt="conf1" width="800"></center>
    在项目配置界面，点击上面 Qt 5.4.0 套件下方 "运行" 按钮，进入该套件运行环境配置：<br>
    <center><img src="images/ch07/ch07-03-11.png" alt="conf2" width="800"></center>
    把 "Run in terminal" 的复选框勾选就行了。<br>
    <br>
    然后点击 QtCreator 左边的 "编辑" 按钮，回到 QtCreator 代码编辑模式，先不编写代码，我们直接生成并运行例子：<br>
    <center><img src="images/ch07/ch07-03-12.png" alt="run1" width="800"></center>
    因为选中了在命令行终端运行，所以现在程序运行时先启动一个命令行，然后在运行图形界面程序，如上图所示。<br>
    <br>
    我们关闭运行中的图形界面程序和命令行，现在开始设计图形界面。<br>
    打开 widget.ui ，进入界面设计模式，按照下图拖入控件：<br>
    <center><img src="images/ch07/ch07-03-13.png" alt="ui" width="800"></center>
    总共只有一行控件：左边的是按钮控件，文本 "接收输入"，对象名 pushButtonIn；<br>
    中间的是单行编辑器，对象名 lineEditMsg；<br>
    右边的是按钮控件，文本 "打印输出"，对象名 pushButtonOut 。<br>
    窗口的主布局器就是水平布局器，点击窗口空白区域，再点击上面水平布局按钮就行了。<br>
    <br>
    这个界面的意义就是点击 "接收输入" 按钮，从命令行提取一行输入，显示到单行编辑器；<br>
    点击 "打印输出" 按钮，我们把单行编辑器里的内容再打印到命令行里面，实现从命令行输入到输出的一套过程。<br>
    <br>
    现在控件和布局设置好了，我们为两个按钮都添加 clicked() 信号对应的槽函数：<br>
    <center><img src="images/ch07/ch07-03-14.png" alt="slot"></center>
    添加好槽函数之后，保存界面文件，关闭界面文件，回到 QtCreator 代码编辑模式。<br>
    我们打开 widget.h 代码看看，这些代码都是自动生成的，不需要手动修改：<br>
    <div class="code"><span style=" color:#000080;">#ifndef</span><span style=" color:#c0c0c0;">
      </span>WIDGET_H
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000080;">#define</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000080;">WIDGET_H</span></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000080;">#include</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">&lt;QWidget&gt;</span></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#808000;">namespace</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#800080;">Ui</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">{</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#808000;">class</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#800080;">Widget</span><span style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">}</span></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#808000;">class</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#800080;">Widget</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">:</span><span style=" color:#c0c0c0;"> </span><span style=" color:#808000;">public</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#800080;">QWidget</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">{</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000080;">Q_OBJECT</span></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#808000;">public</span><span style=" color:#000000;">:</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">explicit</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#800080;">Widget</span><span
style=" color:#000000;">(</span><span style=" color:#800080;">QWidget</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">*</span>parent<span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000080;">0</span><span style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">~</span><span style=" font-style:italic; color:#000000;">Widget</span><span
style=" color:#000000;">();</span></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#808000;">private</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#808000;">slots</span><span style=" color:#000000;">:</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">void</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">on_pushButtonIn_clicked</span><span
style=" color:#000000;">();</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">void</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">on_pushButtonOut_clicked</span><span
style=" color:#000000;">();</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#808000;">private</span><span style=" color:#000000;">:</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800080;">Ui</span><span
style=" color:#000000;">::</span><span style=" color:#800080;">Widget</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">*</span><span style=" color:#800000;">ui</span><span
style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">};</span></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000080;">#endif</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">//</span><span style=" color:#c0c0c0;"> </span><span style=" color:#008000;">WIDGET_H</span></pre>
    </div>
    <br>
    下面我们打开 widget.cpp ，开始编写功能代码，首先是包含的头文件和构造函数：<br>
    <div class="code"><span style=" color:#000080;">#include</span><span style=" color:#c0c0c0;">
      </span><span style=" color:#008000;">"widget.h"</span>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000080;">#include</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">"ui_widget.h"</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000080;">#include</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">&lt;QDebug&gt;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000080;">#include</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">&lt;QTextStream&gt;</span></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#800080;">Widget</span><span style=" color:#000000;">::</span><span
style=" color:#000000;">Widget</span><span style=" color:#000000;">(</span><span
style=" color:#800080;">QWidget</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">*</span><span style=" color:#000000;">parent</span><span
style=" color:#000000;">)</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">:</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800080;">QWidget</span><span
style=" color:#000000;">(</span><span style=" color:#000000;">parent</span><span
style=" color:#000000;">),</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800000;">ui</span><span
style=" color:#000000;">(</span><span style=" color:#808000;">new</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#800080;">Ui</span><span style=" color:#000000;">::</span><span style=" color:#800080;">Widget</span><span
style=" color:#000000;">)</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">{</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800000;">ui</span><span
style=" color:#000000;">-&gt;</span><span style=" color:#000000;">setupUi</span><span
style=" color:#000000;">(</span><span style=" color:#808000;">this</span><span style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">}</span></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#800080;">Widget</span><span style=" color:#000000;">::~</span><span
style=" font-style:italic; color:#000000;">Widget</span><span style=" color:#000000;">()</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">{</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#808000;">delete</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#800000;">ui</span><span style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">}</span></pre>
    </div>
    头文件就增加了调试类 &lt;QDebug&gt; 和 文本流 &lt;QTextStream&gt; ，构造函数和析构函数没有修改代码。<br>
    <br>
    我们来看看 "接收输入" 按钮对应的槽函数代码：<br>
    <div class="code"><span style=" color:#808000;">void</span><span style=" color:#c0c0c0;">
      </span><span style=" color:#800080;">Widget</span><span style=" color:#000000;">::</span><span
        style=" color:#000000;">on_pushButtonIn_clicked</span><span style=" color:#000000;">()</span>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">{</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//输入和输出流</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800080;">QTextStream</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tsIn</span><span style=" color:#000000;">(</span><span
style=" color:#000080;">stdin</span><span style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800080;">QTextStream</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tsOut</span><span
style=" color:#000000;">(</span><span style=" color:#000080;">stdout</span><span
style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//在命令行提示用户输入一行字符串</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800080;">QString</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strOut</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span style=" color:#008000;">"请输入一行字符串："</span><span
style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">tsOut</span><span
style=" color:#000000;">&lt;&lt;</span><span style=" color:#000000;">strOut</span><span
style=" color:#000000;">&lt;&lt;</span>endl<span style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//接收输入</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800080;">QString</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strMsg</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">tsIn</span><span style=" color:#000000;">.</span><span style=" color:#000000;">readLine</span><span
style=" color:#000000;">();</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//显示到单行编辑器</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800000;">ui</span><span
style=" color:#000000;">-&gt;</span><span style=" color:#800000;">lineEditMsg</span><span
style=" color:#000000;">-&gt;</span><span style=" color:#000000;">setText</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strMsg</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">}</span></pre>
    </div>
    因为要在命令行提示用户输入一行字符串，所以需要同时使用输入流 tsIn 和输出流 tsOut。<br>
    定义好 tsIn 和 tsOut 之后，先打印一行提示用户输入的信息到命令行，然后从命令行接收一行字符串输入，保存到 strMsg ，最后将
    strMsg 显示到单行编辑器。<br>
    该函数里与命令行的输入输出交互就是完全通过 QTextStream 两个对象实现的，交互过程很简单，和平常的命令行程序没啥区别。<br>
    <br>
    最后来看看 "打印输出" 按钮对应的槽函数代码：<br>
    <div class="code"><span style=" color:#808000;">void</span><span style=" color:#c0c0c0;">
      </span><span style=" color:#800080;">Widget</span><span style=" color:#000000;">::</span><span
        style=" color:#000000;">on_pushButtonOut_clicked</span><span style=" color:#000000;">()</span>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">{</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//只需要输出流</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800080;">QTextStream</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tsOut</span><span
style=" color:#000000;">(</span><span style=" color:#000080;">stdout</span><span
style=" color:#000000;">);</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//打印一行字符串</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#800080;">QString</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strMsg</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#800000;">ui</span><span style=" color:#000000;">-&gt;</span><span
style=" color:#800000;">lineEditMsg</span><span style=" color:#000000;">-&gt;</span><span
style=" color:#000000;">text</span><span style=" color:#000000;">();</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000000;">tsOut</span><span
style=" color:#000000;">&lt;&lt;</span>endl<span style=" color:#000000;">&lt;&lt;</span><span
style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span style=" color:#008000;">"输出信息："</span><span
style=" color:#000000;">)&lt;&lt;</span><span style=" color:#000000;">strMsg</span><span
style=" color:#000000;">&lt;&lt;</span>endl<span style=" color:#000000;">;</span></pre>
      <pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#008000;">//打印调试信息，也会自动显示到命令行</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;">    </span><span style=" color:#000080;">qDebug</span><span
style=" color:#000000;">()&lt;&lt;</span>endl<span style=" color:#000000;">&lt;&lt;</span><span
style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span style=" color:#008000;">"这行是调试信息。"</span><span
style=" color:#000000;">)&lt;&lt;</span>endl<span style=" color:#000000;">;</span></pre>
      <pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">}</span></pre>
    </div>
    因为只需要输出，所以只用到了 tsOut 。<br>
    我们获取单行编辑器里的文本，然后打印到输出流 tsOut 就搞定了。<br>
    最后的一句 qDebug() 打印调试信息，经过我们上面对项目的修改和运行设置，现在 qDebug()
    会默认把调试信息打印到命令行里面，程序运行时可以在命令行看到调试输出的信息。<br>
    <br>
    例子代码只有上面那些，比较简单，我们生成运行例子，把从输入到输出的过程走一遍，可以看到效果：<br>
    <center><img src="images/ch07/ch07-03-15.png" alt="run2" width="800"></center>
    运行的效果很直观，可以从命令行提取输入信息到单行编辑器，也可以把单行编辑器的信息打印到命令行，qDebug() 调试信息也会自动打印到命令行显示了。<br>
    <br>
    关于 QTextStream
    的内容和例子就讲到这，本节前面内容比如一大堆操作子等列表，不用死记硬背，到需要用的时候再查询文档就可以了。本节三个例子里面关于 QTextStream
    的用法要认真学，比如对文本文件的读写、内存字符串的格式化输入输出、命令行输入输出，这三大用途一定要学会。我们下一节介绍串行化数据流
    QDataStream。<br>
    <br>
    <br>
    <br>
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