compass.watchHeading

At a regular interval, get the compass heading in degrees.

var watchID = navigator.compass.watchHeading(compassSuccess, compassError, [compassOptions]);

Description

The compass is a sensor that detects the direction or heading that the device is pointed. It measures the heading in degrees from 0 to 359.99.

The compass.watchHeading gets the device's current heading at a regular interval. Each time the heading is retrieved, the headingSuccess callback function is executed. Specify the interval in milliseconds via the frequency parameter in the [compassOptions](parameters/compassOptions.html) object.

The returned watch ID references references the compass watch interval. The watch ID can be used with [compass.clearWatch](compass.clearWatch.html) to stop watching the compass.

Supported Platforms

  • Android
  • iPhone
  • Windows Phone 7 ( Mango ) if available in hardware

Quick Example

function onSuccess(heading) {
    var element = document.getElementById('heading');
    element.innerHTML = 'Heading: ' + heading.magneticHeading;
};

function onError(compassError) {
        alert('Compass error: ' + compassError.code);
};

var options = { frequency: 3000 };  // Update every 3 seconds

var watchID = navigator.compass.watchHeading(onSuccess, onError, options);

Full Example

<!DOCTYPE html>
<html>
  <head>
    <title>Compass Example</title>

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

    // The watch id references the current `watchHeading`
    var watchID = null;
    
    // Wait for PhoneGap to load
    //
    document.addEventListener("deviceready", onDeviceReady, false);

    // PhoneGap is ready
    //
    function onDeviceReady() {
        startWatch();
    }

    // Start watching the compass
    //
    function startWatch() {
        
        // Update compass every 3 seconds
        var options = { frequency: 3000 };
        
        watchID = navigator.compass.watchHeading(onSuccess, onError, options);
    }
    
    // Stop watching the compass
    //
    function stopWatch() {
        if (watchID) {
            navigator.compass.clearWatch(watchID);
            watchID = null;
        }
    }
    
    // onSuccess: Get the current heading
    //
    function onSuccess(heading) {
        var element = document.getElementById('heading');
        element.innerHTML = 'Heading: ' + heading.magneticHeading;
    }

    // onError: Failed to get the heading
    //
    function onError(compassError) {
        alert('Compass error: ' + compassError.code);
    }

    </script>
  </head>
  <body>
    <div id="heading">Waiting for heading...</div>
    <button onclick="startWatch();">Start Watching</button>
    <button onclick="stopWatch();">Stop Watching</button>
  </body>
</html>