# Sensor Service API example

This section presents the full source code of a working sample widget for the Sensor Service. You can download the `wgz` package for this widget from section Example widgets.

For general information about creating widgets, see section Widget component files.

For widget development and debugging purposes, this example writes its output to `c:\data\jslog_widget.log` using `console.info`. For instructions on how to enable logging in the Web browser for S60, see section JavaScript console.

### Info.plist

    <?xml version="1.0" encoding="UTF-8"?>
    <!DOCTYPE plist PUBLIC "-//Nokia//DTD PLIST 1.0//EN" "http://www.nokia.com/NOKIA_COM_1/DTDs/plist-1.0.dtd">
    <plist version="1.0">
    <dict>
      <key>DisplayName</key>
      <string>SensorSample</string>
      <key>Identifier</key>
      <string>com.nokia.widget.sapi.sensor.sample</string>
      <key>Version</key>
      <string>1.0</string>
      <key>MainHTML</key>
      <string>sensor-sample.html</string>
    </dict>
    </plist>

### sensor-sample.html

    <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
    <html>
      <head>
        <script type="text/javascript" src="js/common.js"></script>
        <script type="text/javascript" src="js/sensor-sample.js" charset="utf-8"></script>
      </head>
      <body onload='setup()' bgcolor="#ddeeff">
        <form name="frm">
          <h3>Sapi Sensor Sample Widget</h3>
          <input type="button" onclick="findSensorChannel('img1')" value="FindSensorChannel"><img id="img1" src="pic/blank.png" width="25" height="25" align="center"><br>
          <input type="button" onclick="getChannelProperty('img2')" value="GetChannelProperty"><img id="img2" src="pic/blank.png" width="25" height="25" align="center"><br>
          <input type="button" onclick="setChannelProperty('img3')" value="RegisterForNotification"><img id="img5" src="pic/blank.png" width="25" height="25" align="center"><br>
          <input type="button" onclick="stopReceivingNotification('img6')" value="Cancel"><img id="img6" src="pic/blank.png" width="25" height="25" align="center"><hr>
          <div class='sensor' id='sensor' bgcolor="#ddeeff" style=width:100%;height:100%;overflow:auto></div>
        </form>
      </body>
    </html>

### common.js

    // common.js
    //
    // This file contains some utility functions

    // Check the error code and show the information to users
    function checkError(message, resultList, divId, imgId)
    {
      var errCode = resultList.ErrorCode;
      var msg = "";

      if (errCode) {
        msg = message + "<BR>" + "Failed Error: " + errCode + "<BR>";
        if(resultList.ErrorMessage != undefined)
          msg += "Error Message: " + resultList.ErrorMessage;
        showIMG(imgId,"no");
      } else {
        showIMG(imgId,"yes");
      }

      //print error message
      if(divId != null && divId != undefined)
        document.getElementById(divId).innerHTML = msg;
      console.info(msg);

      return errCode;
    }

    // Build the message by reading a iteratorable list in a recursive manner
    function showIterableList(iterator)
    {
      var msg = "";
      try
      {
        iterator.reset();
        var item;
        while (( item = iterator.getNext()) != undefined ){
          msg += showObject( item );
        }
      }
      catch(e)
      {
        alert('<showIterableList> ' + e);
      }
      return msg;
    }

    // Build the message by reading a JS object in a recursive manner
    function showObject( obj )
    {
      var txt = "";
      try {
        if ( typeof obj != 'object' )
          return "" + obj + '<BR/>';
        else {
          for(var key in obj) {
            txt +=  key + ":";
            txt += showObject( obj[key] );
            txt += '<BR/>';
          }
          txt += '<BR/>';
        }
      }
      catch (e)
      {
        alert("showObject: " + e);
      }
      return txt;
    }

    // Show the image to indicate the test result
    function showIMG(imgId, isOK)
    {
      if(imgId == null || imgId == undefined)
        return;

      if(isOK == "yes")
        document.getElementById(imgId).src = "pic/yes.png";
      else if(isOK == "no")
        document.getElementById(imgId).src = "pic/no.png";
      else
        document.getElementById(imgId).src = "pic/blank.png";
    }

    // Show elements in object by using 'alert'
    function testObject(obj)
    {
      var msg = "";
      for(var key in obj) {
        msg = msg + ":" + key + "=" + obj[key];
      }
      alert(msg);
    }

    // Test whether the input is numeric
    function IsNumeric(sText)
    {
      var ValidChars = "0123456789.";
      var IsNumber=true;
      var Char;

      for (i = 0; i < sText.length && IsNumber == true; i++)
      {
        Char = sText.charAt(i);
        if (ValidChars.indexOf(Char) == -1)
        {
          IsNumber = false;
        }
      }
      return IsNumber;
    }

### sensor-sample.js

    // sensor-sample.js
    //
    // In this sample the sensor will be found, get and set;
    // Also, async operation will be canceled.
    //

    // SAPI Error Codes
    // 0  - Success
    // 1000 - InvalidServiceArgument
    // 1001 - UnknownArgumentName
    // 1002 - BadArgumentType
    // 1003 - MissingArgument
    // 1004 - ServiceNotSupported
    // 1005 - ServiceInUse
    // 1006 - ServiceNotReady
    // 1007 - NoMemory
    // 1008 - HardwareNotAvailable
    // 1009 - ServerBusy
    // 1010 - EntryExists
    // 1011 - AccessDenied
    // 1012 - NotFound
    // 1013 - UnknownFormat
    // 1014 - GeneralError
    // 1015 - CancelSuccess
    // 1016 - ServiceTimedOut
    // 1017 - PathNotFound

    // Usage:
    // 1. Call FindSensorChannel (input searchCriterion) - this call obtains a list of maps.The list can be fetched using the key : ReturnValue
    // 2. From the list you need to fetch one ChannelInfo as a map.The fetching depends on how the runtime fetches items from an CLiwDefaultList.
    // 3. It is this ChannelInfo map that needs to be supplied to all the other APIs that follow.

    // Declare the service object
    var so;

    // imgid for callback1 function
    var imgid_callback1;

    // id of the div used to display information
    const DIV_ID = 'sensor';

    // transaction id
    var transactionID;

    // Called from onload()
    function setup()
    {
      try {
        so = device.getServiceObject("Service.Sensor", "ISensor");
        console.info("setup: so: %s", so);
      }
      catch (e) {
        alert('<setup> ' +e);
      }
    }

    //FindSensorChannel - searches and list available sensor channels.
    function findSensorChannel(imgId)
    {
      var criteria = new Object();
      criteria.SearchCriterion = "Rotation";

      try
      {
        var result = so.ISensor.FindSensorChannel(criteria);
        if(!checkError("ISensor::findSensorChannel",result,DIV_ID,imgId)) {
          document.getElementById(DIV_ID).innerHTML = showIterableList(result.ReturnValue);
        }
      }
      catch (e)
      {
        showIMG(imgId,"no");
        alert ("findSensorChannel: " + e);
      }
    }

    // GetChannelProperty
    function getChannelProperty(imgId)
    {
      var channelInfoMap = new Object();
      channelInfoMap.ChannelId = 1;
      channelInfoMap.ContextType = 0;  // 0-not defined; 1- to measure pressure, ...
      channelInfoMap.Quantity = 0;
      channelInfoMap.ChannelType = 0 ;

      var criteria = new Object();
      criteria.PropertyId = "Description";
      criteria.ChannelInfoMap = channelInfoMap;

      try
      {
        var result = so.ISensor.GetChannelProperty(criteria);
        if(!checkError("ISensor::getChannelProperty",result,DIV_ID,imgId)) {
          document.getElementById(DIV_ID).innerHTML = showIterableList(result.ReturnValue);
        }
      }
      catch (e)
      {
        showIMG(imgId,"no");
        alert ("getChannelProperty: " + e);
      }
    }

    // RegisterForNotification - register to receive
    // notification about channel data.
    function registerForNotification(imgId)
    {
      var channelInfoMap = new Object();
      channelInfoMap.ChannelId = 1;
      channelInfoMap.ContextType = 0;  // 0-not defined; 1- to measure pressure, ...
      channelInfoMap.Quantity = 0;
      channelInfoMap.ChannelType = 0 ;

      var criteria = new Object();
      criteria.ListeningType = "ChannelData";
      criteria.ChannelInfoMap = channelInfoMap;

      try
      {
        imgid_callback1 = imgId
        var result = so.ISensor.RegisterForNotification(criteria, callback1);
        transactionID = result.TransactionID;
        if(!checkError("ISensor::registerForNotification",result,DIV_ID,imgId)){
          showIMG(imgId,"");
        }
      }
      catch (e)
      {
        showIMG(imgId,"no");
        alert ("registerForNotification: " + e);
      }
    }

    //Cancel Notification
    function Cancel(imgId)
    {
      var criteria = new Object();
      criteria.TransactionID = transactionID;
      try
      {
        var result = so.ISensor.Cancel(criteria);
        checkError("ISensor::Cancel",result,DIV_ID,imgId)
      }
      catch (e)
      {
        showIMG(imgId,"no");
        alert ("Cancel: " + e);
      }
    }

    // This is the asynchronous callback handler
    function callback1(transId, eventCode, result)
    {
      console.info("callback1: transId: %d  eventCode: %d result.ErrorCode: %d", transId, eventCode, result.ErrorCode);
      if(!checkError("ISensor::registerForNotification",result,DIV_ID,imgid_callback1)) {
        document.getElementById(DIV_ID).innerHTML = "Channel Property changes";
      }
    }