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<td align="right" valign="center"><img src="logo32.png" align="right" width="64" height="32" border="0"></td></tr></table><h1 align=center>QTimer Class Reference</h1>
<p>The QTimer class provides timer signals and single-shot timers.
<a href="#details">More...</a>
<p><tt>#include <<a href="qtimer-h.html">qtimer.h</a>></tt>
<p>Inherits <a href="qobject.html">QObject</a>.
<p><a href="qtimer-members.html">List of all member functions.</a>
<h2>Public Members</h2>
<ul>
<li class=fn><a href="#QTimer"><b>QTimer</b></a> ( QObject * parent = 0, const char * name = 0 )</li>
<li class=fn><a href="#~QTimer"><b>~QTimer</b></a> ()</li>
<li class=fn>bool <a href="#isActive"><b>isActive</b></a> () const</li>
<li class=fn>int <a href="#start"><b>start</b></a> ( int msec, bool sshot = FALSE )</li>
<li class=fn>void <a href="#changeInterval"><b>changeInterval</b></a> ( int msec )</li>
<li class=fn>void <a href="#stop"><b>stop</b></a> ()</li>
<li class=fn>int <a href="#timerId"><b>timerId</b></a> () const</li>
</ul>
<h2>Signals</h2>
<ul>
<li class=fn>void <a href="#timeout"><b>timeout</b></a> ()</li>
</ul>
<h2>Static Public Members</h2>
<ul>
<li class=fn>void <a href="#singleShot"><b>singleShot</b></a> ( int msec, QObject * receiver, const char * member )</li>
</ul>
<hr><a name="details"></a><h2>Detailed Description</h2>
The QTimer class provides timer signals and single-shot timers.
<p>
<p> It uses <a href="qtimerevent.html">timer events</a> internally to
provide a more versatile timer. QTimer is very easy to use:
create a QTimer, call <a href="#start">start</a>() to start it and connect its
<a href="#timeout">timeout</a>() to the appropriate slots. When the time is up it will
emit the timeout() signal.
<p> Note that a QTimer object is destroyed automatically when its
parent object is destroyed.
<p> Example:
<pre>
QTimer *timer = new QTimer( myObject );
<a href="qobject.html#connect">connect</a>( timer, SIGNAL(<a href="#timeout">timeout</a>()), myObject, SLOT(timerDone()) );
timer-><a href="#start">start</a>( 2000, TRUE ); // 2 seconds single-shot timer
</pre>
<p> You can also use the static <a href="#singleShot">singleShot</a>() function to create a
single shot timer.
<p> As a special case, a QTimer with timeout 0 times out as soon as
all the events in the window system's event queue have been
processed.
<p> This can be used to do heavy work while providing a snappy
user interface:
<pre>
QTimer *t = new QTimer( myObject );
<a href="qobject.html#connect">connect</a>( t, SIGNAL(<a href="#timeout">timeout</a>()), SLOT(processOneThing()) );
t-><a href="#start">start</a>( 0, FALSE );
</pre>
<p> myObject->processOneThing() will be called repeatedly and should
return quickly (typically after processing one data item) so that
Qt can deliver events to widgets and stop the timer as soon as it
has done all its work. This is the traditional way of
implementing heavy work in GUI applications; multi-threading is
now becoming available on more and more platforms, and we expect
that null events will eventually be replaced by threading.
<p> Note that QTimer's accuracy depends on the underlying operating
system and hardware. Most platforms support an accuracy of 20ms;
some provide more. If Qt is unable to deliver the requested
number of timer clicks, it will silently discard some.
<p> An alternative to using QTimer is to call <a href="qobject.html#startTimer">QObject::startTimer</a>()
for your object and reimplement the <a href="qobject.html#timerEvent">QObject::timerEvent</a>() event
handler in your class (which must, of course, inherit <a href="qobject.html">QObject</a>).
The disadvantage is that <a href="qobject.html#timerEvent">timerEvent</a>() does not support such
high-level features as single-shot timers or signals.
<p> Some operating systems limit the number of timers that may be
used; Qt tries to work around these limitations.
<p>See also <a href="events.html">Event Classes</a> and <a href="time.html">Time and Date</a>.
<hr><h2>Member Function Documentation</h2>
<h3 class=fn><a name="QTimer"></a>QTimer::QTimer ( <a href="qobject.html">QObject</a> * parent = 0, const char * name = 0 )
</h3>
Constructs a timer called <em>name</em>, with the parent <em>parent</em>.
<p> Note that the parent object's destructor will destroy this timer
object.
<h3 class=fn><a name="~QTimer"></a>QTimer::~QTimer ()
</h3>
Destroys the timer.
<h3 class=fn>void <a name="changeInterval"></a>QTimer::changeInterval ( int msec )
</h3>
Changes the timeout interval to <em>msec</em> milliseconds.
<p> If the timer signal is pending, it will be stopped and restarted;
otherwise it will be started.
<p> <p>See also <a href="#start">start</a>() and <a href="#isActive">isActive</a>().
<h3 class=fn>bool <a name="isActive"></a>QTimer::isActive () const
</h3>
<p> Returns TRUE if the timer is running (pending); otherwise returns
FALSE.
<p>Example: <a href="tutorial1-11.html#x2376">t11/cannon.cpp</a>.
<h3 class=fn>void <a name="singleShot"></a>QTimer::singleShot ( int msec, <a href="qobject.html">QObject</a> * receiver, const char * member )<tt> [static]</tt>
</h3>
This static function calls a slot after a given time interval.
<p> It is very convenient to use this function because you do not need
to bother with a <a href="qobject.html#timerEvent">timerEvent</a> or
to create a local QTimer object.
<p> Example:
<pre>
#include <<a href="qapplication-h.html">qapplication.h</a>>
#include <<a href="qtimer-h.html">qtimer.h</a>>
int main( int argc, char **argv )
{
<a href="qapplication.html">QApplication</a> a( argc, argv );
QTimer::<a href="#singleShot">singleShot</a>( 10*60*1000, &a, SLOT(<a href="qapplication.html#quit">quit</a>()) );
... // create and show your widgets
return a.<a href="qapplication.html#exec">exec</a>();
}
</pre>
<p> This sample program automatically terminates after 10 minutes (i.e.
600000 milliseconds).
<p> The <em>receiver</em> is the receiving object and the <em>member</em> is the
slot. The time interval is <em>msec</em>.
<h3 class=fn>int <a name="start"></a>QTimer::start ( int msec, bool sshot = FALSE )
</h3>
Starts the timer with a <em>msec</em> milliseconds timeout, and returns
the ID of the timer, or zero when starting the timer failed.
<p> If <em>sshot</em> is TRUE, the timer will be activated only once;
otherwise it will continue until it is stopped.
<p> Any pending timer will be stopped.
<p> <p>See also <a href="#singleShot">singleShot</a>(), <a href="#stop">stop</a>(), <a href="#changeInterval">changeInterval</a>(), and <a href="#isActive">isActive</a>().
<p>Examples: <a href="aclock-example.html#x1204">aclock/aclock.cpp</a>, <a href="dirview-example.html#x1704">dirview/dirview.cpp</a>, <a href="distributor-example.html#x2671">distributor/distributor.ui.h</a>, <a href="forever-example.html#x1053">forever/forever.cpp</a>, <a href="hello-example.html#x1639">hello/hello.cpp</a>, <a href="tutorial1-11.html#x2377">t11/cannon.cpp</a>, and <a href="tutorial1-13.html#x2407">t13/cannon.cpp</a>.
<h3 class=fn>void <a name="stop"></a>QTimer::stop ()
</h3>
Stops the timer.
<p> <p>See also <a href="#start">start</a>().
<p>Examples: <a href="dirview-example.html#x1705">dirview/dirview.cpp</a>, <a href="tutorial1-11.html#x2378">t11/cannon.cpp</a>, <a href="tutorial1-12.html#x2400">t12/cannon.cpp</a>, and <a href="tutorial1-13.html#x2408">t13/cannon.cpp</a>.
<h3 class=fn>void <a name="timeout"></a>QTimer::timeout ()<tt> [signal]</tt>
</h3>
<p> This signal is emitted when the timer is activated.
<p>Examples: <a href="aclock-example.html#x1205">aclock/aclock.cpp</a>, <a href="dirview-example.html#x1706">dirview/dirview.cpp</a>, <a href="distributor-example.html#x2672">distributor/distributor.ui.h</a>, <a href="forever-example.html#x1054">forever/forever.cpp</a>, <a href="hello-example.html#x1640">hello/hello.cpp</a>, and <a href="tutorial1-11.html#x2379">t11/cannon.cpp</a>.
<h3 class=fn>int <a name="timerId"></a>QTimer::timerId () const
</h3>
<p> Returns the ID of the timer if the timer is running; otherwise returns
-1.
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