Cordova compass API (navigator.compass.watchHeadin

2019-06-11 08:52发布

站内问答 / JavaScript
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I'm trying to get a sample app running using the cordova compass, but each time the error callback is called with error code 3.

I use cordova V4.0 and of course I added the plugin org.apache.cordova.device-orientation. Here's the code:

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

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

    // The watch id references the current `watchHeading`
    var gWatchID = null;

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

    // device APIs are available
    function onDeviceReady() {
        startWatch();
    }

    // Start watching the compass
    function startWatch() {
        // Update compass every 3 seconds
        var options = { frequency: 3000 };

        if (!gWatchID)
            gWatchID = navigator.compass.watchHeading(onSuccess, onError, options);
    }

    // Stop watching the compass
    function stopWatch() {
        if (gWatchID) {
            navigator.compass.clearWatch(watchID);
            gWatchID = 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>

The app is built, deployed and started successfully. But when it is started, only error code 3 is displayed.

According to the documentation only two error code are definded: CompassError.COMPASS_INTERNAL_ERR = 0; CompassError.COMPASS_NOT_SUPPORTED = 20;

So I wonder what's the meaning error code 3? And what am I doing wrong?

Thanks for your answers, Dante

1条回答
Deceive 欺骗
2楼-- · 2019-06-11 09:49

Either your device does not have a magnetic sensor, or the vendor has not implemented support for it in the OS.

Looking at the Android source code for the device-orientation plugin, the startup code is written like this (modified for brevity):

List<Sensor> list = this.sensorManager.getSensorList(Sensor.TYPE_ORIENTATION);

// If found, then register as listener
if (list != null)
    this.setStatus(CompassListener.STARTING);

// If error, then set status to error
else
    this.setStatus(CompassListener.ERROR_FAILED_TO_START);

Not sure why they made up their own error code there (public static int ERROR_FAILED_TO_START = 3), but really they should be reporting COMPASS_NOT_SUPPORTED as defined in the documentation.

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