public synchronized void onPause() {
   cancel();
   if (registered) {
     activity.unregisterReceiver(powerStatusReceiver);
     registered = false;
   } else {
     Log.w(TAG, "PowerStatusReceiver was never registered?");
   }
 }
 void shutdown() {
   cancel();
 }
 synchronized void onActivity() {
   cancel();
   inactivityTask = new InactivityAsyncTask();
   inactivityTask.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
 }