1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91
|
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en_US" lang="en_US">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<!-- threads.qdoc -->
<title>Qt 4.8: Starting Threads with QThread</title>
<link rel="stylesheet" type="text/css" href="style/offline.css" />
</head>
<body>
<div class="header" id="qtdocheader">
<div class="content">
<a href="index.html" class="qtref"><span>Qt Reference Documentation</span></a>
</div>
<div class="breadcrumb toolblock">
<ul>
<li class="first"><a href="index.html">Home</a></li>
<!-- Breadcrumbs go here -->
<li>Starting Threads with QThread</li>
</ul>
</div>
</div>
<div class="content mainContent">
<link rel="next" href="threads-synchronizing.html" />
<p class="naviNextPrevious headerNavi">
<a class="nextPage" href="threads-synchronizing.html">Synchronizing Threads</a>
</p><p/>
<div class="toc">
<h3><a name="toc">Contents</a></h3>
<ul>
<li class="level1"><a href="#creating-a-thread">Creating a Thread</a></li>
<li class="level1"><a href="#starting-a-thread">Starting a Thread</a></li>
</ul>
</div>
<h1 class="title">Starting Threads with QThread</h1>
<span class="subtitle"></span>
<!-- $$$threads-starting.html-description -->
<div class="descr"> <a name="details"></a>
<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>
<a name="creating-a-thread"></a>
<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="cpp"> <span class="keyword">class</span> MyThread : <span class="keyword">public</span> <span class="type"><a href="qthread.html">QThread</a></span>
{
Q_OBJECT
<span class="keyword">protected</span>:
<span class="type">void</span> run();
};
<span class="type">void</span> MyThread<span class="operator">::</span>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>
</div>
<!-- @@@threads-starting.html -->
<p class="naviNextPrevious footerNavi">
<a class="nextPage" href="threads-synchronizing.html">Synchronizing Threads</a>
</p>
<div class="ft">
<span></span>
</div>
</div>
<div class="footer">
<p>
<acronym title="Copyright">©</acronym> 2012 Nokia Corporation and/or its
subsidiaries. Documentation contributions included herein are the copyrights of
their respective owners.</p>
<br />
<p>
The documentation provided herein is licensed under the terms of the
<a href="http://www.gnu.org/licenses/fdl.html">GNU Free Documentation
License version 1.3</a> as published by the Free Software Foundation.</p>
<p>
Documentation sources may be obtained from <a href="http://www.qt-project.org">
www.qt-project.org</a>.</p>
<br />
<p>
Nokia, Qt and their respective logos are trademarks of Nokia Corporation
in Finland and/or other countries worldwide. All other trademarks are property
of their respective owners. <a title="Privacy Policy"
href="http://en.gitorious.org/privacy_policy/">Privacy Policy</a></p>
</div>
</body>
</html>
|