Sensing

Possible sensors on devices – Documented in SensorEvent class Accelerometer (m/s 2 ) – acceleration in x, y, z axes Magnetic Field (micro Tesla) – ambient magnetic field in x, y, z axes Light (lux) – ambient light level Proximity (cm) Temperature (degrees C) Other

Components of Sensing in Android SensorManager class Sensor class – Additional class (relative to Location) to handle multiple Sensor types – Metadata stored here (name, type, etc.) SensorEvent class – Sensor data stored here SensorEventListener interface – SensorListener interface has been deprecated

SensorManager class

SensorManager Concrete class Gives access to Sensor devices and classes Not instantiated directly – instantiated through the given context’s getSystemService() method Sensor Manager sm = (SensorManager)getSystemService(Context.SENSOR_SERVICE);

SensorManager important methods – getSensorList argument: integer indicating desired sensor type (or all sensors) returns List of all sensors of argument type – getDefaultSensor argument: integer indicating desired sensor type returns device’s sensor of argument type – registerListener arguments: context, sensor, and delay rate – unregisterListener arguments: SensorEventListener and optionally a Sensor

SensorManager Some fields in SensorManager class – Valid delay rates when registering a listener SENSOR_DELAY_X – X: FASTEST, GAME, NORMAL, UI – UI is most standard – good for typical development use – Other constants MAGNETIC_FIELD_EARTH_MAX (or MIN) GRAVITY_X – X: EARTH, MARS, NEPTUNE, etc. – GRAVITY_DEATH_STAR_I (first Star Wars Death Star) » x 10 –7 (of course, this is just an estimate…) Other (LIGHT_X, PRESSURE_STANDARD_ATMOSPHERE, etc.)

Sample code Instantiation SensorManager sm = (SensorManager)getSystemService(Context.SENSOR_SERVICE); Retrieve sensors List ls = sm.getSensorList(Sensor.TYPE_ALL); Retrieve specific sensor Sensor myAccelerometer = sm.getDefaultSensor(Sensor.TYPE_ACCELEROMETER); Registering a listener sm.registerListener(this, sm.getDefaultSensor(Sensor.TYPE_ACCELEROMETER), SensorManager.SENSOR_DELAY_UI); Unregistering a listener sm.unregisterListener(this, sm.getDefaultSensor(Sensor.TYPE_ACCELEROMETER));

Sensor class

Concrete class Represents specific sensor Contains: – methods to obtain general metadata information – fields for specific sensor types

Sensor class important methods – getters for data getName() – returns String value (on Emulator: “Goldfish 3-axis Accelerometer”) getType() – returns int value (1 for Accelerometer) others important fields (all integers) – TYPE_ALL – TYPE_ZZZ (ZZZ is sensor type) ACCELEROMETER, LIGHT, TEMPERATURE, etc.

SensorEvent class

Concrete class Represents an event tied to a specific sensor Contains: – identification of the sensor causing the event – data associated with the event

SensorEvent class no methods (other than Object’s methods) important fields (all public) – sensor, accuracy, and timestamp – values – documented in SensorEvent class float array containing values associated with the sensed information – if sensor is accelerometer » 3 element array with x, y, z axes’ data – if sensor is temperature » 1 element array containing temperature – etc.

SensorEventListener interface

SensorEventListener Interface Notified by SensorManager if status changes SensorManager must register with the SensorEventListener for all desired Sensors

SensorEventListener 2 abstract methods – onAccuracyChanged sensors can have one of four levels of accuracy placement or calibration may affect accuracy parameters are the sensor (Sensor) and the accuracy (int) – onSensorChanged called whenever the value(s) of a Sensor have changed 1 parameter – the SensorEvent

Sample Code – onSensorChanged() public void onSensorChanged(SensorEvent event) { switch (event.sensor.getType()) { case Sensor.TYPE_ACCELEROMETER: ((TextView)findViewById(R.id.tvAccX)).setText("Acc X: " + event.values[0]); ((TextView)findViewById(R.id.tvAccY)).setText("Acc Y: " + event.values[1]); ((TextView)findViewById(R.id.tvAccZ)).setText("Acc Z: " + event.values[2]); break; case Sensor.TYPE_AMBIENT_TEMPERATURE: ((TextView)findViewById(R.id.tvTemp)).setText("Temp: " + event.values[0]); break;...cases continue for all desired sensors... }

SensorEventListener Registering/Unregistering a Manager with a Listener – methods in SensorManager class – take care to utilize resources effectively register in onResume() unregister in onPause()