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<?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">
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<!-- qdeclarativetimer.cpp -->
<title>Qt 4.8: QML Timer Element</title>
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<div class="header" id="qtdocheader">
<div class="content">
<a href="index.html" class="qtref"><span>Qt Reference Documentation</span></a>
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<ul>
<li class="first"><a href="index.html">Home</a></li>
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<li><a href="qdeclarativeelements.html">QML Elements</a></li>
<li>QML Timer Element</li>
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</div>
<div class="content mainContent">
<div class="toc">
<h3><a name="toc">Contents</a></h3>
<ul>
<li class="level1"><a href="#properties">Properties</a></li>
<li class="level1"><a href="#signal-handlers">Signal Handlers</a></li>
<li class="level1"><a href="#methods">Methods</a></li>
<li class="level1"><a href="#details">Detailed Description</a></li>
</ul>
</div>
<h1 class="title">QML Timer Element</h1>
<span class="subtitle"></span>
<!-- $$$Timer-brief -->
<p>The Timer item triggers a handler at a specified interval. <a href="#details">More...</a></p>
<!-- @@@Timer -->
<p>This element was introduced in Qt 4.7.</p>
<ul>
<li><a href="qml-timer-members.html">List of all members, including inherited members</a></li>
</ul>
<a name="properties"></a>
<h2>Properties</h2>
<ul>
<li class="fn"><b><b><a href="qml-timer.html#interval-prop">interval</a></b></b> : int</li>
<li class="fn"><b><b><a href="qml-timer.html#repeat-prop">repeat</a></b></b> : bool</li>
<li class="fn"><b><b><a href="qml-timer.html#running-prop">running</a></b></b> : bool</li>
<li class="fn"><b><b><a href="qml-timer.html#triggeredOnStart-prop">triggeredOnStart</a></b></b> : bool</li>
</ul>
<a name="signal-handlers"></a>
<h2>Signal Handlers</h2>
<ul>
<li class="fn"><b><b><a href="qml-timer.html#onTriggered-signal">onTriggered</a></b></b></li>
</ul>
<a name="methods"></a>
<h2>Methods</h2>
<ul>
<li class="fn"><b><b><a href="qml-timer.html#restart-method">restart</a></b></b></li>
<li class="fn"><b><b><a href="qml-timer.html#start-method">start</a></b></b></li>
<li class="fn"><b><b><a href="qml-timer.html#stop-method">stop</a></b></b></li>
</ul>
<!-- $$$Timer-description -->
<a name="details"></a>
<h2>Detailed Description</h2>
<p>A Timer can be used to trigger an action either once, or repeatedly at a given interval.</p>
<p>Here is a Timer that shows the current date and time, and updates the text every 500 milliseconds. It uses the JavaScript <tt>Date</tt> object to access the current time.</p>
<pre class="qml"> import QtQuick 1.0
<span class="type"><a href="qml-item.html">Item</a></span> {
<span class="type">Timer</span> {
<span class="name">interval</span>: <span class="number">500</span>; <span class="name">running</span>: <span class="number">true</span>; <span class="name">repeat</span>: <span class="number">true</span>
<span class="name">onTriggered</span>: <span class="name">time</span>.<span class="name">text</span> <span class="operator">=</span> <span class="name">Date</span>().<span class="name">toString</span>()
}
<span class="type"><a href="qml-text.html">Text</a></span> { <span class="name">id</span>: <span class="name">time</span> }
}</pre>
<p>The Timer element is synchronized with the animation timer. Since the animation timer is usually set to 60fps, the resolution of Timer will be at best 16ms.</p>
<p>If the Timer is running and one of its properties is changed, the elapsed time will be reset. For example, if a Timer with interval of 1000ms has its <i>repeat</i> property changed 500ms after starting, the elapsed time will be reset to 0, and the Timer will be triggered 1000ms later.</p>
<p><b>See also </b><a href="declarative-toys-clocks.html">Clocks example</a>.</p>
<!-- @@@Timer -->
<h2>Property Documentation</h2>
<!-- $$$interval -->
<div class="qmlitem"><div class="qmlproto"><table class="qmlname"><tr valign="top" class="odd"><td class="tblQmlPropNode"><p><a name="interval-prop"></a><span class="name">interval</span> : <span class="type"><a href="qml-int.html">int</a></span></p></td></tr></table></div><div class="qmldoc"><p>Sets the <i>interval</i> between triggers, in milliseconds.</p>
<p>The default interval is 1000 milliseconds.</p>
</div></div><!-- @@@interval -->
<br/>
<!-- $$$repeat -->
<div class="qmlitem"><div class="qmlproto"><table class="qmlname"><tr valign="top" class="odd"><td class="tblQmlPropNode"><p><a name="repeat-prop"></a><span class="name">repeat</span> : <span class="type"><a href="qml-bool.html">bool</a></span></p></td></tr></table></div><div class="qmldoc"><p>If <i>repeat</i> is true the timer is triggered repeatedly at the specified interval; otherwise, the timer will trigger once at the specified interval and then stop (i.e. running will be set to false).</p>
<p><i>repeat</i> defaults to false.</p>
<p><b>See also </b><a href="qml-timer.html#running-prop">running</a>.</p>
</div></div><!-- @@@repeat -->
<br/>
<!-- $$$running -->
<div class="qmlitem"><div class="qmlproto"><table class="qmlname"><tr valign="top" class="odd"><td class="tblQmlPropNode"><p><a name="running-prop"></a><span class="name">running</span> : <span class="type"><a href="qml-bool.html">bool</a></span></p></td></tr></table></div><div class="qmldoc"><p>If set to true, starts the timer; otherwise stops the timer. For a non-repeating timer, <i>running</i> is set to false after the timer has been triggered.</p>
<p><i>running</i> defaults to false.</p>
<p><b>See also </b><a href="qml-timer.html#repeat-prop">repeat</a>.</p>
</div></div><!-- @@@running -->
<br/>
<!-- $$$triggeredOnStart -->
<div class="qmlitem"><div class="qmlproto"><table class="qmlname"><tr valign="top" class="odd"><td class="tblQmlPropNode"><p><a name="triggeredOnStart-prop"></a><span class="name">triggeredOnStart</span> : <span class="type"><a href="qml-bool.html">bool</a></span></p></td></tr></table></div><div class="qmldoc"><p>When a timer is started, the first trigger is usually after the specified interval has elapsed. It is sometimes desirable to trigger immediately when the timer is started; for example, to establish an initial state.</p>
<p>If <i>triggeredOnStart</i> is true, the timer is triggered immediately when started, and subsequently at the specified interval. Note that if <i>repeat</i> is set to false, the timer is triggered twice; once on start, and again at the interval.</p>
<p><i>triggeredOnStart</i> defaults to false.</p>
<p><b>See also </b><a href="qml-timer.html#running-prop">running</a>.</p>
</div></div><!-- @@@triggeredOnStart -->
<br/>
<h2>Signal Handler Documentation</h2>
<!-- $$$onTriggered -->
<div class="qmlitem"><div class="qmlproto"><table class="qmlname"><tr valign="top" class="odd"><td class="tblQmlFuncNode"><p><a name="onTriggered-signal"></a>Timer::<span class="name">onTriggered</span> ()</p></td></tr></table></div><div class="qmldoc"><p>This handler is called when the Timer is triggered.</p>
</div></div><!-- @@@onTriggered -->
<br/>
<h2>Method Documentation</h2>
<!-- $$$restart -->
<div class="qmlitem"><div class="qmlproto"><table class="qmlname"><tr valign="top" class="odd"><td class="tblQmlFuncNode"><p><a name="restart-method"></a>Timer::<span class="name">restart</span> ()</p></td></tr></table></div><div class="qmldoc"><p>Restarts the timer.</p>
<p>If the Timer is not running it will be started, otherwise it will be stopped, reset to initial state and started. The <tt>running</tt> property will be true following a call to <tt>restart()</tt>.</p>
</div></div><!-- @@@restart -->
<br/>
<!-- $$$start -->
<div class="qmlitem"><div class="qmlproto"><table class="qmlname"><tr valign="top" class="odd"><td class="tblQmlFuncNode"><p><a name="start-method"></a>Timer::<span class="name">start</span> ()</p></td></tr></table></div><div class="qmldoc"><p>Starts the timer.</p>
<p>If the timer is already running, calling this method has no effect. The <tt>running</tt> property will be true following a call to <tt>start()</tt>.</p>
</div></div><!-- @@@start -->
<br/>
<!-- $$$stop -->
<div class="qmlitem"><div class="qmlproto"><table class="qmlname"><tr valign="top" class="odd"><td class="tblQmlFuncNode"><p><a name="stop-method"></a>Timer::<span class="name">stop</span> ()</p></td></tr></table></div><div class="qmldoc"><p>Stops the timer.</p>
<p>If the timer is not running, calling this method has no effect. The <tt>running</tt> property will be false following a call to <tt>stop()</tt>.</p>
</div></div><!-- @@@stop -->
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