How can one get hold of SensorManager?
lazarus / 43-Android

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stab · 2013-08-06 08:26

Hi all,

Would like to be able to get magnetic field readings and need to get
hold of SensorManager.

Have been trying with following code with no luck:

  // get sensorManagerClass
  sensorManagerClass := javaEnvRef^^.FindClass(javaEnvRef,
'android/hardware/SensorManager');
  if sensorManagerClass = nil then
    debugln('******** sensorManagerClass NIL ********')
  else
    debugln('******** sensorManagerClass NOT NIL ********');

  // get the string Context.SENSOR_SERVICE remember that NewStringUTF
does not require ReleaseStringUTFChars
  javaString_SENSORMANAGER_SERVICE :=
javaEnvRef^^.NewStringUTF(javaEnvRef, pchar('SENSOR_SERVICE'));

  // Get the SensorManager object
  lParams[0].l := javaString_SENSORMANAGER_SERVICE;
  sensorManagerObject := javaEnvRef^^.CallObjectMethodA(javaEnvRef,
javaActivityObject, javaMethod_getSystemService, @lParams[0]);
  if sensorManagerObject = nil then
    debugln('******** sensorManagerObject NIL ********')
  else
    debugln('******** sensorManagerObject NOT NIL ********');

  javaMethodId_getDefaultSensor :=
    javaEnvRef^^.GetMethodID(javaEnvRef, sensorManagerClass,
'getDefaultSensor', '(I)Landroid/hardware/Sensor;');
  if javaMethodId_getDefaultSensor = nil then
    debugln('******** javaMethodId_getDefaultSensor NIL ********')
  else
    debugln('******** javaMethodId_getDefaultSensor NOT NIL
********');

From this code I find sensorManagerClass and
javaMethodId_getDefaultSensor but
sensorManagerObject is nil.

Reading documentation for SensorManager and code used from java
public class Test extends Activity implements SensorEventListener {
    private SensorManager mgr;
    private Sensor compass;
    private TextView text;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        mgr = (SensorManager) this.getSystemService(SENSOR_SERVICE);

        compass = mgr.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD);

My conclusion is that one should use SENSOR_SERVICE as parameter to
get hold of SensorManager but that doesn't work.

Any hint on this will be appreciated

Regards
stab