license: Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE file distributed with this work for additional information regarding copyright ownership. The ASF licenses this file to you under the Apache License, Version 2.0 (the “License”); you may not use this file except in compliance with the License. You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

     Unless required by applicable law or agreed to in writing,
     software distributed under the License is distributed on an
     "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
     KIND, either express or implied.  See the License for the
     specific language governing permissions and limitations
     under the License.

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 should be used with geolocation.clearWatch to stop watching for changes in position.

Description

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 callback is invoked with a Position object as the parameter. If there is an error, the geolocationError callback is invoked with a PositionError object.

Supported Platforms

Android
BlackBerry WebWorks (OS 5.0 and higher)
iOS
Windows Phone 7 ( Mango )
Bada 1.2 & 2.x
webOS

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: throw an error if no update is received every 30 seconds.
//
var watchID = navigator.geolocation.watchPosition(onSuccess, onError, { timeout: 30000 });

Full Example

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

    <script type="text/javascript" charset="utf-8" src="cordova-1.8.1.js"></script>
    <script type="text/javascript" charset="utf-8">

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

    var watchID = null;

    // Cordova is ready
    //
    function onDeviceReady() {
        // Throw an error if no update is received every 30 seconds
        var options = { timeout: 30000 };
        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 object
    //
    function onError(error) {
        alert('code: '    + error.code    + '\n' +
              'message: ' + error.message + '\n');
    }

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