--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Symbian3/SDK/Source/GUID-E5B5C3CA-B256-5B29-AB90-590676444C85.dita	Thu Jan 21 18:18:20 2010 +0000
@@ -0,0 +1,42 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. -->
+<!-- This component and the accompanying materials are made available under the terms of the License 
+"Eclipse Public License v1.0" which accompanies this distribution, 
+and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". -->
+<!-- Initial Contributors:
+    Nokia Corporation - initial contribution.
+Contributors: 
+-->
+<!DOCTYPE concept
+  PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
+<concept id="GUID-E5B5C3CA-B256-5B29-AB90-590676444C85" xml:lang="en"><title>How
+to start a periodic timer</title><shortdesc>Provides code snippets to show you how to start a periodic timer</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>
+<p>A periodic timer, <codeph>CPeriodic</codeph>, invokes a function at regular
+intervals. You must wrap the function to be called in a <codeph>TCallBack</codeph>. </p>
+<p>First, we provide a callback function for the timer to call. The callback
+function can be a static member, i.e. <codeph>TInt X::Foo(TAny *)</codeph> or
+global, i.e. <codeph>TInt Foo(TAny *)</codeph>. The <codeph>TAny*</codeph> can
+point to any object that we specify when we start the timer.</p>
+<p>It is awkward to deal with <codeph>TAny*</codeph>, and more convenient
+to write handler code from a non-static member function, so here we code a
+static function to invoke a non-static function <codeph>DoTick()</codeph> as
+follows:</p>
+<codeblock id="GUID-8D673BE4-1F28-58E0-868D-98B48DD91C60" xml:space="preserve">TInt CPeriodicRunner::Tick(TAny* aObject)
+    {
+    // cast, and call non-static function
+    ((CPeriodicRunner*)aObject)-&gt;DoTick();
+    return 1;
+    }
+</codeblock>
+<p>The next piece of code creates a <codeph>CPeriodic</codeph> and sets it
+off with one-second ticks. The callback is specified to call the static <codeph>Tick()</codeph> function,
+passing the <codeph>this</codeph> pointer (which we use in <codeph>Tick()</codeph> to
+call <codeph>DoTick()</codeph>).</p>
+<codeblock id="GUID-092F13DD-9158-5245-A1FE-101EFB305D15" xml:space="preserve">void CPeriodicRunner::StartTimer()
+    {
+    const TInt tickInterval=1000000;
+    iPeriodic=CPeriodic::NewL(0); // neutral priority
+    iPeriodic-&gt;StartInMicroSeconds(tickInterval,tickInterval,TCallBack(Tick, this));
+    }
+</codeblock>
+</conbody></concept>
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