Android旋转箭头到GPS位置

Question

我正在Android中实现一项功能，将箭头指向GPS位置。 根据本教程http://www.javacodegeeks.com/2013/09/android-compass-code-example.html。最初，onSensorChanged事件中的代码会将指南针指向真正的北方，现在我在onSensorChanged事件中更改了代码以指向我的GPS位置，如下所示：

@Override
public void onSensorChanged(SensorEvent event) {

    // get the angle around the z-axis rotated
    float degree = Math.round(event.values[0]);

    /*----------------This is the code I added to the original code------*/
    Location currentLoc = // get location from GPS or network
    GeomagneticField geoField = new GeomagneticField(
         (float) currentLoc.getLatitude(),
         (float) currentLoc.getLongitude(),
         (float) currentLoc.getAltitude(),
         System.currentTimeMillis());
    degree += geoField.getDeclination();
    /*----------------------------------------------------------------------*/

    tvHeading.setText("Heading: " + Float.toString(degree) + " degrees");

    // create a rotation animation (reverse turn degree degrees)
    RotateAnimation ra = new RotateAnimation(
            currentDegree, 
            -degree,
            Animation.RELATIVE_TO_SELF, 0.5f, 
            Animation.RELATIVE_TO_SELF,
            0.5f);

    // how long the animation will take place
    ra.setDuration(210);

    // set the animation after the end of the reservation status
    ra.setFillAfter(true);

    // Start the animation
    image.startAnimation(ra);
    currentDegree = -degree;

}

但经过一些测试，它并没有指向正确的位置。任何人都可以帮我解释或解释我做错了什么。

非常感谢。