Are Android's BroadcastReceivers started in a new thread?

Question

If I have an inner class that extends BroadcastReceiver within my Service class, should I care about synchronization, when the BroadcastRecei

Answer 1

Android Broadcast receivers are by default start in GUI thread (main thread) if you use RegisterReceiver(broadcastReceiver, intentFilter).

But it can be run in a worker thread as follows;

When using a HandlerThread, be sure to exit the thread after unregistering the BroadcastReceiver. If not, File Descriptor (FD) leaks occur in Linux level and finally the application gets crashed if continue to Register / Unregister.

unregisterReceiver(...);

Then looper.quit(); Or looper.quitSafely();

private Handler broadcastReceiverHandler = null;
private HandlerThread broadcastReceiverThread = null;
private Looper broadcastReceiverThreadLooper = null;

private BroadcastReceiver broadcastReceiverReadScans = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {

    }
}

private void registerForIntents() {
    broadcastReceiverThread = new HandlerThread("THREAD_NAME");//Create a thread for BroadcastReceiver
    broadcastReceiverThread.start();

    broadcastReceiverThreadLooper = broadcastReceiverThread.getLooper();
    broadcastReceiverHandler = new Handler(broadcastReceiverThreadLooper);

    IntentFilter filterScanReads = new IntentFilter();
    filterScanReads.addAction("ACTION_SCAN_READ");
    filterScanReads.addCategory("CATEGORY_SCAN");

    context.registerReceiver(broadcastReceiverReadScans, filterScanReads, null, broadcastReceiverHandler);
}

private void unregisterIntents() {
    context.unregisterReceiver(broadcastReceiverReadScans);
    broadcastReceiverThreadLooper.quit();//Don't forget
}