1. Sensors – Part I
SE 395/595

2. Topics Overview of Android sensor types Overview of Sensors Framework
Sensor class
SensorManager class
SensorEvent class
SensorEventListener class
Supported Sensor Types
Basic elements of sensor utilization
Accelerometer Example

3. Android Sensors Motion Position Environmental Rotation Acceleration
Orientation
Location
Environmental
Ambient Temperature
Barometric pressure
Light intensity
Humidity

4. Android Sensors Framework
Three main classes to work with:
SensorManager class
Request access to sensors
Assign sensor event listeners
Sensor class
Encapsulates details of a particular sensor instance
SensorEvent
Encapsulation of new sensor data (data, type, accuracy, timestamp)
SensorEventListener
Responds to changes in value or accuracy for a sensor

5. Sensor.TYPE_<Sensor Type>
List at:
ACCELEROMETER (1)
AMBIENT_TEMEPRATURE (13)
GRAVITY (9)
GYROSCOPE (4)
LIGHT (5)
LINEAR_ACCELERATION (10)
MAGNETIC_FIELD (2)
ORIENATION (deprecated)
PRESSURE (6)
PROXIMITY (8)
RELATIVE_HUMIDITY (12)
ROTATION_VECTOR (11)
TEMPERATURE (deprecated)

6. Sensor Manager Class
Must request the service in your application’s onCreate method
//Get Sensor Manager Instance
_sensorManager = (SensorManager)
getSystemService(Context.SENSOR_SERVICE);

7. Sensor Class Methods Identification Methods: Performance Methods:
getName() – name of the snesor
getType() - what category of component is it?
getVendor() – Who makes it?
getVersion() – Which version of this component are we working with?
Performance Methods:
getPower() – “power” in mA draw
getResolution() – resolution of the sensor’s measurements
getMaximumRange() – maximum
getMinimumDelay() – minimum time interval for updates
Non-zero - streaming at the specified interval
Zero – Reports only when changed
Get it all!!!
toString()

8. Sensor Manager Class: Obtain List of All Sensors
public void printAllSensors() {
List<Sensor> sensors = _sensorManager.getSensorList(Sensor.TYPE_ALL);
for (Sensor s :sensors) {
Log.i("SensorDetails", s.toString()); }

9. Sample Output
:59:17.310: I/SensorDetails(28379): {Sensor name="MPL Gyroscope", vendor="Invensense", version=1, type=4, maxRange= , resolution= , power=5.5, minDelay=1000}
:59:17.310: I/SensorDetails(28379): {Sensor name="MPL Raw Gyroscope", vendor="Invensense", version=1, type=16, maxRange= , resolution= , power=5.5, minDelay=1000}
:59:17.310: I/SensorDetails(28379): {Sensor name="MPL Accelerometer", vendor="Invensense", version=1, type=1, maxRange= , resolution= , power=5.5, minDelay=1000}
:59:17.310: I/SensorDetails(28379): {Sensor name="MPL Magnetic Field", vendor="Invensense", version=1, type=2, maxRange=5461.0, resolution=0.9, power=0.15, minDelay=10000}
:59:17.310: I/SensorDetails(28379): {Sensor name="MPL Raw Magnetic Field", vendor="Invensense", version=1, type=14, maxRange=5461.0, resolution=0.9, power=0.15, minDelay=10000}
:59:17.310: I/SensorDetails(28379): {Sensor name="MPL Orientation", vendor="Invensense", version=1, type=3, maxRange=360.0, resolution=1.0E-5, power=11.15, minDelay=5000}
:59:17.310: I/SensorDetails(28379): {Sensor name="MPL Rotation Vector", vendor="Invensense", version=1, type=11, maxRange=1.0, resolution=1.0E-5, power=11.15, minDelay=5000}

10. SensorEventListener Class
Activity may implement the listener interface
Class inherits interface
Class creates an instance of an object that implements the listener interface
Two methods must be implemented
public void onAccuracyChanged(Sensor sensor, int accuracy)
public void onSensorChaged(SensorEvent event)

11. Sensor Event Class
sensor – instance of Sensor class for sensor that generated the data
values – array stores raw values from the sensor
e.g. If type is TYPE_ACCELEROMETER
event.values[0] – acceleration along x-axis
event.values[1] – acceleration along y-axis
event.values[2] – acceleration along z-axis
accuracy – flag for sensor accuracy
SensorManger.SENSOR_STATUS_ACCURACY_LOW
timestamp – time of event in nanoseconds

12. Android Coordinate System
Source:

13. Accelerometer Example
Let’s write a simple app
Displays x, y, and z axes accelerations in m/s^2
Layout
Appropriate text fields
Class
Implement SensorEventListener
Create stubs for its methods
onCreate – create a sensor manager instance for accelerometer
onResume – register this class as listener for accelerometer
onPause – pause unregister
onSensorChanged
Set text views from layout to the accelerometer values: values[0], values[1], and values[2]

14. Accelerometer Application Demo
Demonstration of the accelerometer class

15. References Android.com, “Sensors Overview | Android Developers”, 2013.
Android.com. SensorEvent Reference