Just a quick $.02: 1. On some phones it is possible that sensor accuracy may be unreliable always and never change - not likely, but possible, I've seen that with at least one of the sensors, where the reported accuracy never changed - so be sure that's not nerfing your code there, that check you have for event.accuracy.
2. I like the deprecated orientation sensor, I'm probably in the minority though. 3. most implementations I've seen copy the event.values since the array you get back is re-used, and you may be waiting for 2 events before you fuse the values, but that's probably not a problem if it's working for you on many phones On Tuesday, July 10, 2012 6:39:32 AM UTC-4, Nik Cain wrote: > > Hi, > > My app relies heavily on having a compass bearing (it's an open source app > at https://github.com/ShowMeHills/ShowMeHills). Most of the devices work > ok, but on one of my devices I don't get any events from the magnetic field > sensor. > > The device is an Xperia Arc (Lt15i), Android 2.3.4. Quite possibly the > sensor is broken as after googling I've found no-one else seeing the > problem. So I didn't worry about it too much initially. > > However I'm seeing users of other phones reporting that the app doesn't > work while other compass apps do, which obviously makes my app look > terrible (an HTC esspresso phone apparently). I'm assuming either the other > apps are falling back to using the deprecated Orientation sensor, or I've > missed something subtle which most phones are not worrying about (but some > do). > > As far as I know I don't think I'm doing anything wrong - my main activity > class sets up the listener with; > > mSensorManager = (SensorManager)getSystemService(SENSOR_SERVICE); > > accelerometer = > mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER); > magnetometer = > mSensorManager.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD); > > mSensorManager.registerListener(this, accelerometer, > SensorManager.SENSOR_DELAY_GAME); > mSensorManager.registerListener(this, magnetometer, > SensorManager.SENSOR_DELAY_GAME); > > (unregistering and reregistering in pause/resume), then has the listener > which is like; > > public void onSensorChanged(SensorEvent event) { > if (event.accuracy == SensorManager.SENSOR_STATUS_UNRELIABLE) { > return; > } > > 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[] rotationMatrixA = mRotationMatrixA; > if (SensorManager.getRotationMatrix(rotationMatrixA, null, > mGravity, mGeomagnetic)) { > > do my compass bearing calculation... > } > > > The problem is that I never get a magnetic field event (only accelerometer > events), so never get to do my bearing calculation. I assume I can't do > SensorManager.getRotationMatrix without BOTH of those values? Otherwise I > think that's all normal stuff. > > However, the phone's TYPE_ORIENTATION events do work. The trouble is I'm > confused as to how to transform the coordinates so that I get a compass > bearing in the direction of the camera (ie handset isn't flat, it's held up > while looking at the view - landscape mode). I've managed this with the > accelerator/magnetic matrices, but then there were lots of help online for > that - I've not found any examples of transposing the orientation matrix. > Plus it's deprecated, so I doubt it's the smart thing to fall back to. > > So has anyone any ideas why some phones don't fire magnetic sensor events > (which is broken - my code or my phone)? Or failing that a snippet of code > to orient; > > if (event.sensor.getType() == Sensor.TYPE_ORIENTATION) > { > float azimuth_angle = event.values[0]; > float pitch_angle = event.values[1]; > float roll_angle = event.values[2]; > ..bearing = ? > > into a compass bearing when the handset is orientated as > Surface.ROTATION_90 (landscape, camera facing away from you looking at the > view). > > Thanks, > Nik > -- You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
