안드로이드 기기 회전각도 구하기

안드로이드 센서값을 읽어서 회전정도를 구하는게 필요해서 방법을 찾았는데 검색해서 나오는 것들 대부분이 구버전이라 4.4에서 쓸려고 하니 depress 뜨길래 요즘꺼(?)에 맞는 방법으로 찾아서 쓴거 정리 해둠

public class Activity_Main extends Activity  implements SensorEventListener{
 
    private SensorManager mSensorManager;
    private Sensor accelerometer;
    private Sensor magnetometer;
 	private float[] mGravity = null;
	private float[] mGeomagnetic= null;
	private float R[] = new float[9];
	private float I[] = new float[9];
    
    //-----------------------------------------------------------
    
	@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 onPause() {
		super.onPause();
		mSensorManager.unregisterListener(this);
	}

    @Override
    protected void onResume() {
    	super.onResume();
    	mSensorManager.registerListener(this, accelerometer, SensorManager.SENSOR_DELAY_UI);
    	mSensorManager.registerListener(this, magnetometer, SensorManager.SENSOR_DELAY_UI);
    }
 
	@Override
	public void onAccuracyChanged(Sensor sensor, int accuracy) {
		// TODO Auto-generated method stub
		
	}

	@Override
	public void onSensorChanged(SensorEvent event) {
		if (event.sensor.getType() == Sensor.TYPE_ACCELEROMETER)
			mGravity = event.values;
		if (event.sensor.getType() == Sensor.TYPE_MAGNETIC_FIELD)
			mGeomagnetic = event.values;
		if (mGravity != null && mGeomagnetic != null) {
			boolean success = SensorManager.getRotationMatrix(R, I, mGravity, mGeomagnetic);
			if (success) {
				float orientation[] = new float[3];
				SensorManager.getOrientation(R, orientation);
				double degreeY =  Math.toDegrees(orientation[2]);
			}
		}
	}
}