SensorEventListener doesn't get unregistered with unregisterListener() method

Question

I have very simple Android app: in activity I have a button and I start/stop the OrientationListener. However, after unregistering it, in ddms I can still see the thread

Answer 1

I'm having the same problem. I checked the Android code. The relevant code is in SensorManager.java

private void unregisterListener(Object listener) {
    if (listener == null) {
        return;
    }

    synchronized (sListeners) {
        final int size = sListeners.size();
        for (int i=0 ; i<size ; i++) {
            ListenerDelegate l = sListeners.get(i);
            if (l.getListener() == listener) {
                sListeners.remove(i);
                // disable all sensors for this listener
                for (Sensor sensor : l.getSensors()) {
                    disableSensorLocked(sensor);
                }
                break;
            }
        }
    }
}

and

        public void run() {
            //Log.d(TAG, "entering main sensor thread");
            final float[] values = new float[3];
            final int[] status = new int[1];
            final long timestamp[] = new long[1];
            Process.setThreadPriority(Process.THREAD_PRIORITY_URGENT_DISPLAY);

            if (!open()) {
                return;
            }

            synchronized (this) {
                // we've open the driver, we're ready to open the sensors
                mSensorsReady = true;
                this.notify();
            }

            while (true) {
                // wait for an event
                final int sensor = sensors_data_poll(sQueue, values, status, timestamp);

                int accuracy = status[0];
                synchronized (sListeners) {
                    if (sensor == -1 || sListeners.isEmpty()) {
                        // we lost the connection to the event stream. this happens
                        // when the last listener is removed or if there is an error
                        if (sensor == -1 && !sListeners.isEmpty()) {
                            // log a warning in case of abnormal termination
                            Log.e(TAG, "_sensors_data_poll() failed, we bail out: sensors=" + sensor);
                        }
                        // we have no more listeners or polling failed, terminate the thread
                        sensors_destroy_queue(sQueue);
                        sQueue = 0;
                        mThread = null;
                        break;
                    }
                    final Sensor sensorObject = sHandleToSensor.get(sensor);
                    if (sensorObject != null) {
                        // report the sensor event to all listeners that
                        // care about it.
                        final int size = sListeners.size();
                        for (int i=0 ; i<size ; i++) {
                            ListenerDelegate listener = sListeners.get(i);
                            if (listener.hasSensor(sensorObject)) {
                                // this is asynchronous (okay to call
                                // with sListeners lock held).
                                listener.onSensorChangedLocked(sensorObject,
                                        values, timestamp, accuracy);
                            }
                        }
                    }
                }
            }
            //Log.d(TAG, "exiting main sensor thread");
        }
    }
}

So it looks like the thread should be terminated when there are no listeners any more