AirTV-Qt/qtsingleapplication/doc/html/qtsingleapplication-example-trivial.html

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  15 </tr></table><h1 class="title">A Trivial Example<br /><span class="subtitle"></span>
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  17 <p>The application in this example has a log-view that displays messages sent by further instances of the same application.</p>
  18 <p>The example demonstrates the use of the <a href="qtsingleapplication.html">QtSingleApplication</a> class to detect and communicate with a running instance of the application using the sendMessage() API. The messageReceived() signal is used to display received messages in a <a href="http://qt.nokia.com/doc/4.6/qtextedit.html">QTextEdit</a> log.</p>
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  57
  58  #include &lt;qtsingleapplication.h&gt;
  59  #include &lt;QtGui/QTextEdit&gt;
  60
  61  class TextEdit : public QTextEdit
  62  {
  63      Q_OBJECT
  64  public:
  65      TextEdit(QWidget *parent = 0)
  66          : QTextEdit(parent)
  67      {}
  68  public slots:
  69      void append(const QString &amp;str)
  70      {
  71          QTextEdit::append(str);
  72      }
  73  };
  74
  75  #include &quot;main.moc&quot;
  76
  77  int main(int argc, char **argv)
  78  {
  79      QtSingleApplication instance(argc, argv);</pre>
  80 <p>The example has only the <tt>main</tt> entry point function. A <a href="qtsingleapplication.html">QtSingleApplication</a> object is created immediately.</p>
  81 <pre>     if (instance.sendMessage(&quot;Wake up!&quot;))
  82          return 0;</pre>
  83 <p>If another instance of this application is already running, sendMessage() will succeed, and this instance just exits immediately.</p>
  84 <pre>     TextEdit logview;
  85      logview.setReadOnly(true);
  86      logview.show();</pre>
  87 <p>Otherwise the instance continues as normal and creates the user interface.</p>
  88 <pre>     instance.setActivationWindow(&amp;logview);
  89
  90      QObject::connect(&amp;instance, SIGNAL(messageReceived(const QString&amp;)),
  91                       &amp;logview, SLOT(append(const QString&amp;)));
  92
  93      return instance.exec();</pre>
  94 <p>The <tt>logview</tt> object is also set as the application's activation window. Every time a message is received, the window will be raised and activated automatically.</p>
  95 <p>The messageReceived() signal is also connected to the <a href="http://qt.nokia.com/doc/4.6/qtextedit.html">QTextEdit</a>'s append() slot. Every message received from further instances of this application will be displayed in the log.</p>
  96 <p>Finally the event loop is entered.</p>
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