Android Kompass zeigt auf meinen Standort statt Norden

Question

Ich entwickle Kompass-Anwendung, wo ich möchte, dass der Kompass auf eine bestimmte Breitengrad-Position statt des üblichen Nordens zeigt. Ich habe einige questions zu meinem Problem gefunden, aber ich schaffe es nicht, dass sie für mich funktionieren. Hier ist mein Code:

public class MainActivity extends AppCompatActivity implements SensorEventListener { 
    private ImageView image; 
    private float currentDegree = 0f; 
    private SensorManager mSensorManager; 
    private TextView tvHeading; 
    private Location location = new Location("A"); 
    private Location target = new Location("B"); 
    private LocationManager locationManager; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 

     image = (ImageView) findViewById(R.id.imageViewCompass); 
     tvHeading = (TextView) findViewById(R.id.tvHeading); 

     mSensorManager = (SensorManager) getSystemService(SENSOR_SERVICE); 

     location.setLatitude(54.903535); 
     location.setLongitude(23.979342); 

     target.setLatitude(54.904618); 
     target.setLongitude(23.978782); 
    } 

    @Override 
    protected void onResume() { 
     super.onResume(); 

     mSensorManager.registerListener(this, mSensorManager.getDefaultSensor(Sensor.TYPE_ORIENTATION), 
       SensorManager.SENSOR_DELAY_GAME); 
    } 

    @Override 
    protected void onPause() { 
     super.onPause(); 
     mSensorManager.unregisterListener(this); // to stop the listener and save battery 
    } 

    @Override 
    public void onSensorChanged(SensorEvent event) { 
     float degree = Math.round(event.values[0]); 
     tvHeading.setText("Heading: " + Float.toString(degree) + " degrees"); 
     RotateAnimation ra = new RotateAnimation(
       currentDegree, 
       -degree, 
       Animation.RELATIVE_TO_SELF, 0.5f, 
       Animation.RELATIVE_TO_SELF, 
       0.5f); 
     ra.setDuration(210); 
     ra.setFillAfter(true); 

     image.startAnimation(ra); 
     currentDegree = -degree; 
    } 

    @Override 
    public void onAccuracyChanged(Sensor sensor, int accuracy) { 
     // not in use 
    } 
} 

derzeit zeigt mein Zeiger nur in Norden statt meiner Zielort harcoded.

Answer 1

Ich glaube, ich den Weg gefunden, es zu tun: Hier ist die Methode, die ich geändert haben das erwartete Verhalten zu bekommen (Basierend auf this Frage und Cookie Antwort)

@Override 
    public void onSensorChanged(SensorEvent event) { 
     // get the angle around the z-axis rotated 
     float degree = Math.round(event.values[0]); 
     degree += geoField.getDeclination(); 

     float bearing = location.bearingTo(target); 
     degree = (bearing - degree) * -1; 
     degree = normalizeDegree(degree); 

     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; 
    } 

private float normalizeDegree(float value) { 
     if (value >= 0.0f && value <= 180.0f) { 
      return value; 
     } else { 
      return 180 + (180 + value); 
     } 
    }