//
                // Android 2.2 has introduced a new way of handling headset
                // action button presses. This involves registering to handle
                // the button presses every time one needs it and unregistering
                // once the button events are no longer needed. Last app to
                // register gets the focus.
                //
                
                ...
                
                //
                // Register am event receiver for ACTION_MEDIA_BUTTON events,
                // and adjust its priority to make sure we get these events
                // before any media player which hijacks the button presses.
                //
                IntentFilter intentFilter = new IntentFilter(Intent.ACTION_MEDIA_BUTTON);
                intentFilter.setPriority(IntentFilter.SYSTEM_HIGH_PRIORITY - 1);
                service.registerReceiver(headsetButtonReceiver, intentFilter);