Android app: Basic accelerometer

AccelerometerActivity.java

public class AccelerometerActivity extends ActionBarActivity implements SensorEventListener{
    
    //...
    private TextView acceleration;
    private SensorManager sm;
    private Sensor accelerometer;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_accelerometer);
        
        //get sensor manager service and init accelerometer sensor already existing
        sm = (SensorManager) getSystemService(SENSOR_SERVICE);
        accelerometer = sm.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
        startSensor();

        //get acceleration values shown on screen
        acceleration = (TextView) findViewById(R.id.acceleration);
        //...
        // added button to stop sensor and quit the app
        Button myButton = (Button) findViewById(R.id.button_exit);
        myButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                stopSensor();
                finish();
            }
        });
    }

    @Override
    protected void onResume() {
        super.onResume();
        startSensor();
    }
    
    @Override
    public void onAccuracyChanged(Sensor sensor, int accuracy) {
        //Do nothing
    }
    
    @Override
    public void onSensorChanged(SensorEvent event) {
        //every time the sensor captures an event, the view is updated with the new values
        Acceleration capturedAcceleration = getAccelerationFromSensor(event);
        updateTextView(capturedAcceleration);
        //...
    }

    private void updateTextView(Acceleration capturedAcceleration) {
        acceleration.setText("X:" + capturedAcceleration.getX() +
                "\nY:" + capturedAcceleration.getY() +
                "\nZ:" + capturedAcceleration.getZ() +
                "\nTimestamp:" + capturedAcceleration.getTimestamp());
    }

    private void startSensor() {
        sm.registerListener(this, accelerometer, SensorManager.SENSOR_DELAY_NORMAL);
    }

    private void stopSensor() {
        sm.unregisterListener(this);
    }
    
    private Acceleration getAccelerationFromSensor(SensorEvent event) {
        //format timestamp 
        long timestamp = (new Date()).getTime() + (event.timestamp - System.nanoTime()) / 1000000L;
        
        //create a new acceleration bean with X,Y and Z axes values and timestamp
        return new Acceleration(event.values[0], event.values[1], event.values[2], timestamp);
    }
   
   //... 
}