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title: geolocation.watchPosition

geolocation.watchPosition

Watches for changes to the device's current position.

var watchId = navigator.geolocation.watchPosition(geolocationSuccess,
                                                  [geolocationError],
                                                  [geolocationOptions]);

Parameters

geolocationSuccess: The callback that is called with the current position.
geolocationError: (Optional) The callback that is called if there was an error.
geolocationOptions: (Optional) The geolocation options.

Returns

String: returns a watch id that references the watch position interval. The watch id can be used with [geolocation.clearWatch](geolocation.clearWatch.html) to stop watching for changes in position.

Description

Function geolocation.watchPosition is an asynchronous function. It returns the device's current position when a change in position has been detected. When the device has retrieved a new location, the [geolocationSuccess](parameters/geolocationSuccess.html) callback is invoked with a [Position](Position/position.html) object as the parameter. If there is an error, the [geolocationError](parameters/geolocationError.html) callback is invoked with a [PositionError](PositionError/positionError.html) object.

Supported Platforms

Android
BlackBerry (OS 4.6)
BlackBerry WebWorks (OS 5.0 and higher)
iPhone
Windows Phone 7 ( Mango )

Quick Example

// onSuccess Callback
//   This method accepts a `Position` object, which contains
//   the current GPS coordinates
//
function onSuccess(position) {
    var element = document.getElementById('geolocation');
    element.innerHTML = 'Latitude: '  + position.coords.latitude      + '<br />' +
                        'Longitude: ' + position.coords.longitude     + '<br />' +
                        '<hr />'      + element.innerHTML;
}

// onError Callback receives a PositionError object
//
function onError(error) {
    alert('code: '    + error.code    + '\n' +
          'message: ' + error.message + '\n');
}

// Options: retrieve the location every 3 seconds
//
var watchID = navigator.geolocation.watchPosition(onSuccess, onError, { frequency: 3000 });

Full Example

<!DOCTYPE html>
<html>
  <head>
    <title>Device Properties Example</title>

    <script type="text/javascript" charset="utf-8" src="cordova-1.5.0.js"></script>
    <script type="text/javascript" charset="utf-8">

    // Wait for PhoneGap to load
    //
    document.addEventListener("deviceready", onDeviceReady, false);

    var watchID = null;

    // PhoneGap is ready
    //
    function onDeviceReady() {
        // Update every 3 seconds
        var options = { frequency: 3000 };
        watchID = navigator.geolocation.watchPosition(onSuccess, onError, options);
    }

    // onSuccess Geolocation
    //
    function onSuccess(position) {
        var element = document.getElementById('geolocation');
        element.innerHTML = 'Latitude: '  + position.coords.latitude      + '<br />' +
                            'Longitude: ' + position.coords.longitude     + '<br />' +
                            '<hr />'      + element.innerHTML;
    }

    // onError Callback receives a [PositionError](PositionError/positionError.html) object
    //
    function onError(error) {
        alert('code: '    + error.code    + '\n' +
              'message: ' + error.message + '\n');
    }

    </script>
  </head>
  <body>
    <p id="geolocation">Watching geolocation...</p>
  </body>
</html>