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<h1 class="title">Starting Threads with QThread<br /><span class="subtitle"></span>
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<p>A <a href="qthread.html">QThread</a> instance represents a thread and provides the means to <a href="qthread.html#start">start()</a> a thread, which will then execute the reimplementation of <a href="qthread.html#run">QThread::run</a>(). The <tt>run()</tt> implementation is for a thread what the <tt>main()</tt> entry point is for the application. All code executed in a call stack that starts in the <tt>run()</tt> function is executed by the new thread, and the thread finishes when the function returns. <a href="qthread.html">QThread</a> emits signals to indicate that the thread started or finished executing.</p>
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<h2>Creating a Thread</h2>
<p>To create a thread, subclass <a href="qthread.html">QThread</a> and reimplement its <a href="qthread.html#run">run()</a> function. For example:</p>
<pre> class MyThread : public QThread
{
Q_OBJECT
protected:
void run();
};
void MyThread::run()
{
...
}</pre>
<a name="starting-a-thread"></a>
<h2>Starting a Thread</h2>
<p>Then, create an instance of the thread object and call <a href="qthread.html#start">QThread::start</a>(). Note that you must create the <a href="qapplication.html">QApplication</a> (or <a href="qcoreapplication.html">QCoreApplication</a>) object before you can create a <a href="qthread.html">QThread</a>.</p>
<p>The function will return immediately and the main thread will continue. The code that appears in the <a href="qthread.html#run">run()</a> reimplementation will then be executed in a separate thread.</p>
<p>Creating threads is explained in more detail in the <a href="qthread.html">QThread</a> documentation.</p>
<p>Note that <a href="qcoreapplication.html#exec">QCoreApplication::exec</a>() must always be called from the main thread (the thread that executes <tt>main()</tt>), not from a <a href="qthread.html">QThread</a>. In GUI applications, the main thread is also called the GUI thread because it's the only thread that is allowed to perform GUI-related operations.</p>
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