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    10 <!DOCTYPE concept

    11   PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">

    12 <concept id="GUID-078E6232-31FA-5582-84B8-F5E3E4B14A05" xml:lang="en"><title>How

    13 to start a heartbeat timer</title><shortdesc>Provides code snippet to show you how to start a heartbeat timer.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

    14 <p>A heartbeat timer, <codeph>CHeartbeat</codeph>, invokes a function at regular

    15 intervals. You must define a class that implements the <codeph>MBeating</codeph> interface

    16 to define:</p>

    17 <ul>

    18 <li id="GUID-5B54CE88-DE53-5635-BBF4-639B693C5BEC"><p>a function <codeph>Beat()</codeph> that

    19 is called if the heartbeat timer is in synchronisation with the system clock</p> </li>

    20 <li id="GUID-E20AD2FD-B847-52B6-8D1E-F01B2A971ABA"><p>a function <codeph>Synchronize()</codeph> that

    21 is called if the heartbeat timer has got out of synchronisation with the system

    22 clock</p> </li>

    23 </ul>

    24 <p>First, we define a class <codeph>CHeartbeatRunner</codeph> class that derives

    25 from <codeph>MBeating</codeph>. </p>

    26 <codeblock id="GUID-6D0B8C93-7F24-5002-A8FF-5C9F4C41EE7B" xml:space="preserve">class CHeartbeatRunner: public MBeating

    27     {

    28 public:

    29     // Implement MBeating

    30     void Beat();

    31     void Synchronize();

    32 

    33     // Start timer

    34     void StartTimer();

    35 private:

    36     CHeartbeat* iHeartbeat;

    37 };</codeblock>

    38 <p>Then, we can start the heartbeat timer. We pass the time interval for the

    39 beats (allowable intervals are defined in 1/12s of a second by <codeph>TTimerLockSpec</codeph>),

    40 and the object implementing <codeph>MBeating</codeph>.</p>

    41 <codeblock id="GUID-C0BD2194-9FED-5C2B-B900-A028210CF78C" xml:space="preserve">void CHeartbeatRunner::StartTimer()

    42     {

    43     iHeartbeat=CHeartbeat::NewL(0); // neutral priority

    44     iHeartbeat->Start(ETwelveOClock,this); // 1 second intervals

    45     }</codeblock>

    46 </conbody></concept>