Android-Position Sensors

The Android platform provides two sensors that let you determine the position of a device: the geomagnetic field sensor and the orientation sensor.

Note: The orientation sensor was deprecated in Android 2.2 (API Level 8).

》Using the Game Rotation Vector Sensor

The following code shows you how to get an instance of the default game rotation vector sensor:

private SensorManager mSensorManager;private Sensor mSensor;...mSensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);mSensor = mSensorManager.getDefaultSensor(Sensor.TYPE_GAME_ROTATION_VECTOR);

》Using the Geomagnetic Rotation Vector Sensor

The following code shows you how to get an instance of the default geomagnetic rotation vector sensor:

private SensorManager mSensorManager;private Sensor mSensor;...mSensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);mSensor = mSensorManager.getDefaultSensor(Sensor.TYPE_GEOMAGNETIC_ROTATION_VECTOR);

》Using the Orientation Sensor

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The orientation sensor lets you monitor the position of a device relative to the earth's frame of reference (specifically, magnetic north). The following code shows you how to get an instance of the default orientation sensor:

private SensorManager mSensorManager;private Sensor mSensor;...mSensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);mSensor = mSensorManager.getDefaultSensor(Sensor.TYPE_ORIENTATION);

》The following code sample shows how to acquire orientation data directly from the orientation sensor. We recommend that you do this only if a device has negligible roll.

public class SensorActivity extends Activity implements SensorEventListener {  private SensorManager mSensorManager;  private Sensor mOrientation;  @Override  public void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.main);    mSensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);    mOrientation = mSensorManager.getDefaultSensor(Sensor.TYPE_ORIENTATION);  }  @Override  public void onAccuracyChanged(Sensor sensor, int accuracy) {    // Do something here if sensor accuracy changes.    // You must implement this callback in your code.  }  @Override  protected void onResume() {    super.onResume();    mSensorManager.registerListener(this, mOrientation, SensorManager.SENSOR_DELAY_NORMAL);  }  @Override  protected void onPause() {    super.onPause();    mSensorManager.unregisterListener(this);  }  @Override  public void onSensorChanged(SensorEvent event) {    float azimuth_angle = event.values[0];    float pitch_angle = event.values[1];    float roll_angle = event.values[2];    // Do something with these orientation angles.  }}

》Using the Geomagnetic Field Sensor

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The geomagnetic field sensor lets you monitor changes in the earth's magnetic field. The following code shows you how to get an instance of the default geomagnetic field sensor:

private SensorManager mSensorManager;private Sensor mSensor;...mSensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);mSensor = mSensorManager.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD);

》Using the Uncalibrated Magnetometer

private SensorManager mSensorManager;private Sensor mSensor;...mSensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);mSensor = mSensorManager.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD_UNCALIBRATED);

》Using the Proximity Sensor

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The proximity sensor lets you determine how far away an object is from a device. The following code shows you how to get an instance of the default proximity sensor:

private SensorManager mSensorManager;private Sensor mSensor;...mSensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);mSensor = mSensorManager.getDefaultSensor(Sensor.TYPE_PROXIMITY);

》

public class SensorActivity extends Activity implements SensorEventListener {  private SensorManager mSensorManager;  private Sensor mProximity;  @Override  public final void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.main);    // Get an instance of the sensor service, and use that to get an instance of    // a particular sensor.    mSensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);    mProximity = mSensorManager.getDefaultSensor(Sensor.TYPE_PROXIMITY);  }  @Override  public final void onAccuracyChanged(Sensor sensor, int accuracy) {    // Do something here if sensor accuracy changes.  }  @Override  public final void onSensorChanged(SensorEvent event) {    float distance = event.values[0];    // Do something with this sensor data.  }  @Override  protected void onResume() {    // Register a listener for the sensor.    super.onResume();    mSensorManager.registerListener(this, mProximity, SensorManager.SENSOR_DELAY_NORMAL);  }  @Override  protected void onPause() {    // Be sure to unregister the sensor when the activity pauses.    super.onPause();    mSensorManager.unregisterListener(this);  }}

Note: Some proximity sensors return binary values that represent "near" or "far." In this case, the sensor usually reports its maximum range value in the far state and a lesser value in the near state. Typically, the far value is a value > 5 cm, but this can vary from sensor to sensor. You can determine a sensor's maximum range by using the getMaximumRange() method.