The problem is in the assigment of mGravity
and mGeomagnetic
it should be event.values.clone()
. mGravity has class scope but, by using mGravity = event.values, you assign its value to a value in an address that has method scope. So as soon as onSensorChanged is called again and it is magnetic type, the mGravity is now pointing to a variable which no longer exists and thus can have any value.
Android magnetometer returning random values
-
29-03-2022 - |
Domanda
I am building an Android application which logs the degrees of the compass of the device into a file. There are two methods the get this degrees:
Method 1:
SensorManager mSensorManager = (SensorManager) getSystemService(SENSOR_SERVICE);
Sensor orientationSensor = mSensorManager.getDefaultSensor(Sensor.TYPE_ORIENTATION);
mSensorManager.registerListener(this, orientationSensor, SensorManager.SENSOR_DELAY_NORMAL);
public void onSensorChanged(SensorEvent event) {
float azimuthInDegrees = event.values[0]
}
Method 2:
SensorManager mSensorManager = (SensorManager) getSystemService(SENSOR_SERVICE);
Sensor accelerometer = mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
Sensor magnetometer = mSensorManager.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD);
mSensorManager.registerListener(this, accelerometer, SensorManager.SENSOR_DELAY_NORMAL);
mSensorManager.registerListener(this, magnetometer, SensorManager.SENSOR_DELAY_NORMAL);
float[] mGravity;
float[] mGeomagnetic;
public void onSensorChanged(SensorEvent event) {
if (event.sensor.getType() == Sensor.TYPE_ACCELEROMETER) {
mGravity = event.values;
}
if (event.sensor.getType() == Sensor.TYPE_MAGNETIC_FIELD) {
mGeomagnetic = event.values;
}
if (mGravity != null && mGeomagnetic != null) {
float R[] = new float[9];
float I[] = new float[9];
boolean success = SensorManager.getRotationMatrix(R, I, mGravity, mGeomagnetic);
if (success) {
float orientation[] = new float[3];
SensorManager.getOrientation(R, orientation);
float azimuthInDegress = ((float) Math.toDegrees(orientation[0]) + 360) % 360;
}
}
}
I tried out both methods by placing my device in the North direction (which is around 360 degrees):
Method 1 returns perfect results but unfortunately this method is deprecated:
- 359.6567
- 359.5034
- 359.859
- 359.76212
- 359.8878
- 359.87048
- 359.8356
- 359.80356
- 359.81192
- 359.7671
- 359.84668
- 359.88528
Method 2 also returns good results but sometimes (randomly) it returns an incorrect degree:
- 359.91495
- 359.83652
- 263.67697
- 359.67993
- 359.70038
- 359.688
- 359.71155
- 359.70276
- 359.6984
- 359.6429
- 270.6323
- 359.62302
- 359.49954
- 359.44757
- 359.47803
- 359.4947
- 359.39572
As you can see, some incorrect degrees are randomly returned with the second method. The device is calibrated and I think that the problem is with the second method as the first method returns perfect results. Can you guys help me out?
Soluzione
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