Full example to calculate bearing in Android, useful in augmented reality apps.
I wrote this example to thank you to all users that have posted in interner some kind of solution to solve bearing calculation.
The "engine" is BearingSensor class that initializes sensors, get data from them and apply some formulas to received data:
BearingSensor class initializes and uses these sensors: gravity, accelerometer and magnetometer sensors.
this.mGravity = this.mSensorManager.getDefaultSensor( Sensor.TYPE_GRAVITY );
haveGravity = this.mSensorManager.registerListener( mSensorEventListener, this.mGravity, SensorManager.SENSOR_DELAY_GAME );
this.mAccelerometer = this.mSensorManager.getDefaultSensor( Sensor.TYPE_ACCELEROMETER );
haveAccelerometer = this.mSensorManager.registerListener( mSensorEventListener, this.mAccelerometer, SensorManager.SENSOR_DELAY_GAME );
this.mMagnetometer = this.mSensorManager.getDefaultSensor( Sensor.TYPE_MAGNETIC_FIELD );
haveMagnetometer = this.mSensorManager.registerListener( mSensorEventListener, this.mMagnetometer, SensorManager.SENSOR_DELAY_GAME );
BearingSensor class retrieves data using SensorManager listener:
@Override
public void onAccuracyChanged( Sensor sensor, int accuracy );
@Override
public void onSensorChanged( SensorEvent event );
onAccuracyChanged is not important, so its body is empty.
In onSensorChanged we get data from sensors and apply some formulas on them, using
SensorManager.getRotationMatrix
to obtain rotation matrix from sensor data, then
SensorManager.remapCoordinateSystem
to apply a remapping of coordinate system due to device orientation, finally
SensorManager.getOrientation
to compute the device's orientation based on the rotation matrix.
To use BearingSensor you have to instantiate it passing a context instance and the listener that will receive bearing changes.
public class MainActivity extends AppCompatActivity implements BearingSensor.BearingSensorListener {
private BearingSensor bearingSensor;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
bearingSensor = new BearingSensor(this, this);
}
@Override
public void onBearingSensorAngleChanged(int azimuth) {
Log.i("BearingSensor", String.format("%d degrees", azimuth));
}
@Override
public void onResume()
{
super.onResume();
bearingSensor.start();
}
@Override
public void onPause()
{
super.onPause();
bearingSensor.stop();
}
}
The callback
public void onBearingSensorAngleChanged(int azimuth);
contains azimuth parameter that indicates current angle from north pole in degrees.