SL4A SensorManagerFacade

Exposes the SensorManager related functionality.

Guidance notes
For reasons of economy the sensors on smart phones are usually low cost and, therefore, low accuracy (usually represented by 10 bit data). The floating point data values obtained from sensor readings have up to 16 decimal places, the majority of which are noise. On many phones the accelerometer is limited (by the phone manufacturer) to a maximum reading of 2g. The magnetometer (which also provides orientation readings) is strongly affected by the presence of ferrous metals and can give large errors in vehicles, on board ship etc.

Following a startSensingTimed(A,B) api call sensor events are entered into the Event Queue (see EventFacade). For the A parameter: 1 = All Sensors, 2 = Accelerometer, 3 = Magnetometer and 4 = Light. The B parameter is the minimum delay between recordings in milliseconds. To avoid duplicate readings the minimum delay should be 20 milliseconds. The light sensor will probably be much slower (taking about 1 second to register a change in light level). Note that if the light level is constant no sensor events will be registered by the light sensor.

Following a startSensingThreshold(A,B,C) api call sensor events greater than a given threshold are entered into the Event Queue. For the A parameter: 1 = Orientation, 2 = Accelerometer, 3 = Magnetometer and 4 = Light. The B parameter is the integer value of the required threshold level. For orientation sensing the integer threshold value is in milliradians. Since orientation events can exceed the threshold value for long periods only crossing and return events are recorded. The C parameter is the required axis (XYZ) of the sensor: 0 = No axis, 1 = X, 2 = Y, 3 = X+Y, 4 = Z, 5= X+Z, 6 = Y+Z, 7 = X+Y+Z. For orientation X = azimuth, Y = pitch and Z = roll.

Example (python)

 import android, time
 droid = android.Android()
 droid.startSensingTimed(1, 250)
 time.sleep(1)
 s1 = droid.readSensors().result
 s2 = droid.sensorsGetAccuracy().result
 s3 = droid.sensorsGetLight().result
 s4 = droid.sensorsReadAccelerometer().result
 s5 = droid.sensorsReadMagnetometer().result
 s6 = droid.sensorsReadOrientation().result
 droid.stopSensing()
 

Returns:
s1 = {u'accuracy': 3, u'pitch': -0.47323511242866517, u'xmag': 1.75, u'azimuth': -0.26701245009899138, u'zforce': 8.4718560000000007, u'yforce': 4.2495484000000001, u'time': 1297160391.2820001, u'ymag': -8.9375, u'zmag': -41.0625, u'roll': -0.031366908922791481, u'xforce': 0.23154590999999999}
s2 = 3 (Highest accuracy)
s3 = None ---(not available on many phones)
s4 = [0.23154590999999999, 4.2495484000000001, 8.4718560000000007] ----(x, y, z accelerations)
s5 = [1.75, -8.9375, -41.0625] -----(x, y, z magnetic readings)
s6 = [-0.26701245009899138, -0.47323511242866517, -0.031366908922791481] ---(azimuth, pitch, roll in radians)

readSensors	Returns the most recently recorded sensor data.
sensorsGetAccuracy	Returns the most recently received accuracy value.
sensorsGetLight	Returns the most recently received light value.
sensorsReadAccelerometer	Returns the most recently received accelerometer values. returns: (List) a List of Floats [(acceleration on the) X axis, Y axis, Z axis].
sensorsReadMagnetometer	Returns the most recently received magnetic field values. returns: (List) a List of Floats [(magnetic field value for) X axis, Y axis, Z axis].
sensorsReadOrientation	Returns the most recently received orientation values. returns: (List) a List of Doubles [azimuth, pitch, roll].
startSensing	Starts recording sensor data to be available for polling. sampleSize (Integer) number of samples for calculating average readings (default=5) Deprecated in 4. Use startSensingTimed or startSensingThreshhold instead.
startSensingThreshold	Records to the Event Queue sensor data exceeding a chosen threshold. sensorNumber (Integer) 1 = Orientation, 2 = Accelerometer, 3 = Magnetometer and 4 = Light threshold (Integer) Threshold level for chosen sensor (integer) axis (Integer) 0 = No axis, 1 = X, 2 = Y, 3 = X+Y, 4 = Z, 5= X+Z, 6 = Y+Z, 7 = X+Y+Z
startSensingTimed	Starts recording sensor data to be available for polling. sensorNumber (Integer) 1 = All, 2 = Accelerometer, 3 = Magnetometer and 4 = Light delayTime (Integer) Minimum time between readings in milliseconds
stopSensing	Stops collecting sensor data.