Android direction sensor

Question

is it possible to know which direction the phone is pointing while looking at the camera preview, or do you have to have the phone flat like a compass.

Thanks

Answer 1

Yes - The following code should do the job

public class Test extends Activity  implements SensorEventListener{

    public static float swRoll;
    public static float swPitch;
    public static float swAzimuth;


    public static SensorManager mSensorManager;
    public static Sensor accelerometer;
    public static Sensor magnetometer;

    public static float[] mAccelerometer = null;
    public static float[] mGeomagnetic = null;


    public void onAccuracyChanged(Sensor sensor, int accuracy) {
    }

    @Override
    public void onSensorChanged(SensorEvent event) {
        // onSensorChanged gets called for each sensor so we have to remember the values
        if (event.sensor.getType() == Sensor.TYPE_ACCELEROMETER) {
            mAccelerometer = event.values;
        }

        if (event.sensor.getType() == Sensor.TYPE_MAGNETIC_FIELD) {
            mGeomagnetic = event.values;
        }

        if (mAccelerometer != null && mGeomagnetic != null) {
            float R[] = new float[9];
            float I[] = new float[9];
            boolean success = SensorManager.getRotationMatrix(R, I, mAccelerometer, mGeomagnetic);

            if (success) {
                float orientation[] = new float[3];
                SensorManager.getOrientation(R, orientation);
                // at this point, orientation contains the azimuth(direction), pitch and roll values.
                  double azimuth = 180 * orientation[0] / Math.PI;
                  double pitch = 180 * orientation[1] / Math.PI;
                  double roll = 180 * orientation[2] / Math.PI;
            }
        }
    }



    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mSensorManager = (SensorManager)getSystemService(SENSOR_SERVICE);
        accelerometer = mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
        magnetometer = mSensorManager.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD);
    }

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

        mSensorManager.registerListener(this, accelerometer, SensorManager.SENSOR_DELAY_GAME);
        mSensorManager.registerListener(this, magnetometer, SensorManager.SENSOR_DELAY_GAME);
    }

    @Override
    protected void onPause() {
        super.onPause();
        mSensorManager.unregisterListener(this, accelerometer);
        mSensorManager.unregisterListener(this, magnetometer);
    }
}