<?xml version="1.0" encoding="utf-8"?>+
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<!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. -->+
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<!-- This component and the accompanying materials are made available under the terms of the License +
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"Eclipse Public License v1.0" which accompanies this distribution, +
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and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". -->+
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<!-- Initial Contributors:+
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    Nokia Corporation - initial contribution.+
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Contributors: +
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-->+
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<!DOCTYPE task+
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  PUBLIC "-//OASIS//DTD DITA Task//EN" "task.dtd">+
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<task id="GUID-E93EE459-8CF4-42A1-B06C-E78E56FD25A0" xml:lang="en"><title>Listening+
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for Property Changes</title><shortdesc>The sensor channel APIs enable the client applications to be notified+
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about the changes to properties associated with a sensor channel.</shortdesc><prolog><metadata><keywords/></metadata></prolog><taskbody>+
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<prereq id="GUID-D1D22060-E453-4046-953D-10486D45885F"> Before listening for+
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the property changes of a sensor channel, you must <xref href="GUID-4B709839-8EEF-4AD2-9868-9AF0176B1E5B.dita#GUID-4B709839-8EEF-4AD2-9868-9AF0176B1E5B/GUID-FBBD3A8B-F240-4DC0-B516-3A51FDD86A88">open the sensor channel</xref>.         </prereq>+
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<context id="GUID-0D960123-7430-42B5-A84D-B63F2852DD7C"><p>The client applications+
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can use the property listener to monitor the property changes made by other+
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clients.</p></context>+
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<steps id="GUID-4DD07DEC-6017-4237-BE46-1D69E5FBD744-GENID-1-6-1-8-1-1-6-1-4-1-4-1-8-1-3-3">+
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<step id="GUID-9A69E5AD-E938-4092-A8C2-CB65C37C8962-GENID-1-6-1-8-1-1-6-1-4-1-4-1-8-1-3-3-1"><cmd>Create a property+
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listener implementation for the <parmname>MSensrvPropertyListener</parmname> interface.</cmd>+
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<stepxmp><codeblock xml:space="preserve">class PropertyListener:public MSensrvPropertyListener+
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    {+
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    public:    +
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    void PropertyChanged(CSensrvChannel &amp;aChannel, const TSensrvProperty &amp;aChangedProperty)+
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        {+
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        ...+
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         //Implementation+
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        }+
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    void PropertyError(CSensrvChannel &amp;aChannel, TSensrvErrorSeverity aError)+
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        {+
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        ...+
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         //Implementation+
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        }+
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    void SetPropertySuccessIndicationChanged(TSetPropertySuccessIndicator aIndication)+
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        {+
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        ...+
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         //Implementation+
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        }+
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    void GetPropertyListenerInterfaceL(TUid aInterfaceUid, TAny *&amp;aInterface)+
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        {+
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        ...+
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         //Implementation+
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        }+
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    };</codeblock></stepxmp>+
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</step>+
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<step id="GUID-6AB619B9-0259-493A-BC40-CAF5BF337E04"><cmd>Start property listening+
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by passing an instance of property listener implementation using <xref href="GUID-22DC917F-D833-3531-AB2D-A6E2D52EF844.dita#GUID-22DC917F-D833-3531-AB2D-A6E2D52EF844/GUID-4552066A-4FC1-3876-89AA-DC9B081B3814"><apiname>CSensrvChannel::SetPropertyListenerL()</apiname></xref>.</cmd>+
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<stepxmp><codeblock xml:space="preserve">//Instance of the property listener implementation+
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PropertyListener propListener;+
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...+
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CSensrvChannel* channel;+
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...+
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channel-&gt;SetPropertyListenerL(&amp;propListener);+
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...</codeblock></stepxmp>+
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<info>When a property change occurs, a <parmname>PropertyChanged()</parmname> notification+
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is delivered through the <parmname>MSensrvPropertyListener</parmname> callback+
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interface to the clients that are listening for property changes.<note> The+
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client that set the property is not notified.</note></info>+
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</step>+
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<step id="GUID-8AD85E3B-EBBC-41E4-A32C-AF2A52B018E6"><cmd>Once you get the+
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required property changes associated with the sensor channel, you can stop+
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property listening by passing a NULL parameter to the <xref href="GUID-22DC917F-D833-3531-AB2D-A6E2D52EF844.dita#GUID-22DC917F-D833-3531-AB2D-A6E2D52EF844/GUID-4552066A-4FC1-3876-89AA-DC9B081B3814"><apiname>CSensrvChannel::SetPropertyListenerL()</apiname></xref> function.</cmd>+
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<stepxmp><codeblock xml:space="preserve">channel-&gt;SetPropertyListenerL();</codeblock></stepxmp>+
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</step>+
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</steps>+
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</taskbody></task>+
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