Professional Android 4 Application Development

Monitoring a Device’s Movement and Orientation x 495
3. Add a calibration constant that represents the acceleration due to gravity:
private final double calibration = SensorManager.STANDARD_GRAVITY;
4. Create a new SensorEventListener implementation that sums the acceleration detected
along each axis and negates the acceleration due to gravity. It should update the current (and
possibly maximum) acceleration whenever a change in acceleration is detected:
private final SensorEventListener sensorEventListener = new SensorEventListener() {
public void onAccuracyChanged(Sensor sensor, int accuracy) { }
public void onSensorChanged(SensorEvent event) {
double x = event.values[0];
double y = event.values[1];
double z = event.values[2];
double a = Math.round(Math.sqrt(Math.pow(x, 2) +
Math.pow(y, 2) +
Math.pow(z, 2)));
currentAcceleration = Math.abs((float)(a-calibration));
}
};
if (currentAcceleration > maxAcceleration)
maxAcceleration = currentAcceleration;
5. Update the onCreate method to get a reference to the two Text Views and the Sensor
Manager:
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
accelerationTextView = (TextView)findViewById(R.id.acceleration);
maxAccelerationTextView = (TextView)findViewById(R.id.maxAcceleration);
sensorManager = (SensorManager)getSystemService(Context.SENSOR_SERVICE);
6. Override the onResume handler to register your new Listener for accelerometer updates using
the SensorManager:
@Override
protected void onResume() {
super.onResume();
Sensor accelerometer = sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
sensorManager.registerListener(sensorEventListener,
accelerometer,
SensorManager.SENSOR_DELAY_FASTEST);
}