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<!DOCTYPE task

  PUBLIC "-//OASIS//DTD DITA Task//EN" "task.dtd">

<task id="GUID-44FDDA27-1A5D-42B5-8DE0-D9E88EB75C93" xml:lang="en"><title>Querying

for Sensor Channels</title><shortdesc>You can retrieve a list of sensor channels that are available for

a particular sensor type. Once you get the list of sensor channels that are

active, you can perform any required operations such as configuring sensor

channel properties, controlling sensor channels and so on.</shortdesc><prolog><metadata><keywords/></metadata></prolog><taskbody>

<steps id="GUID-4DD07DEC-6017-4237-BE46-1D69E5FBD744-GENID-1-7-1-8-1-1-8-1-4-1-5-1-4-1-3-1">

<step id="GUID-EE1655E2-D4C4-4593-A0E1-BD1DFACB0351"><cmd>Create an instance

of <codeph>TSensrvChannelInfo</codeph> and set the required channel type as

the search criteria. For example, to query for all double tapping channels

provided by accelerometer sensor, set the channel type as <codeph>KSensrvChannelTypeIdAccelerometerDoubleTappingData</codeph>.</cmd>

<stepxmp><codeblock xml:space="preserve">TSensrvChannelInfo channelInfo;

channelInfo.iChannelType = KSensrvChannelTypeIdAccelerometerDoubleTappingData;</codeblock></stepxmp>

</step>

<step id="GUID-176936C5-17FE-49A6-A0A7-0E76EB69C5E8"><cmd>Create an instance

of <codeph>CSensrvChannelFinder</codeph> class and use the <xref href="GUID-5F108D03-C8A6-3EF9-B103-2E8916633602.dita#GUID-5F108D03-C8A6-3EF9-B103-2E8916633602/GUID-E58BAF1B-57AA-3E85-A4F9-8C6C29043FBD"><apiname>CSensrvChannelFinder::FindChannelsL()</apiname></xref> function

to query for available sensor channels.</cmd>

<stepxmp><codeblock xml:space="preserve">CSensrvChannelFinder* finder = CSensrvChannelFinder::NewL();

finder-&gt;FindChannelsL(channelList, searchParameters);</codeblock></stepxmp>

</step>

<step id="GUID-9A69E5AD-E938-4092-A8C2-CB65C37C8962-GENID-1-7-1-8-1-1-8-1-4-1-5-1-4-1-3-1-3"><cmd>Create an instance

of <codeph>RSensrvChannelInfoList</codeph> to store the list of sensor channels.</cmd>

<stepxmp><codeblock xml:space="preserve">RSensrvChannelInfoList channelInfoList;</codeblock></stepxmp>

</step>

</steps>

<result id="GUID-F26EFE38-DF01-4531-89AD-191049E31F36">       <p>The <parmname>channelInfoList</parmname> contains

all the double tapping channels that are found. If several matching channels

are found, you can select the required channel by examining the content of

channel information objects inside <parmname>channelInfoList</parmname>.</p> 

   </result>

<example><p>This following code shows how to find double tapping channels

for accelerometer sensor:</p><codeblock xml:space="preserve">.....

......

/Construct a channel finder.

    CSensrvChannelFinder* channelFinder;

    channelFinder = CSensrvChannelFinder::NewL();

    CleanupStack::PushL( channelFinder );

    // to store list of found channels.

    RSensrvChannelInfoList channelInfoList;

    //Create and fill channel search criteria.

    //In this example double tapping channel is searched.

    TSensrvChannelInfo channelInfo;

    channelInfo.iChannelType = KSensrvChannelTypeIdAccelerometerDoubleTappingData;

    //Find the double tapping channel

    channelFinder->FindChannelsL( channelInfoList, channelInfo );

    CleanupStack::PopAndDestroy( channelFinder ); // finder not needed any more

    if( channelInfoList.Count() != 1 )

        {

        //The device does not support double tapping channel or

        //there are several double tapping channels.

        }

    else

        {

        //double tapping channel found 

        }

.....

....

</codeblock></example>