From my records it seems that SensorEventListener.onSensorChanged callback is called by the same thread that registered the callback. I.e there must be some message-queue synchronization going on in the background which allows the activitys UI-Thread to handle the callbacks.

That leads to my question: Is there a need to synchronize SensorEventListener.onSensorChanged with the activitys UI-thread, assuming that the activitys UI-thread registered the SensorEventListener?

I cannot find any documentation references, but can see various examples calling invalidate() unsychronized or synchronize the entire callback.

I used something along the lines of

Log.i(TAG, "" + Thread.currentThread().getId()); 

to retrieve threading information.

I'm running android 2.1 update1.

Best regards, Christoph