Java – Is it possible to block the UI thread when displaying an alert dialog

I have this method, which basically waits for the items in the singleton queue to become empty, there is a running background service that stops once it deletes all the items in the queue and processes them one by one. This code runs in the main thread, what happens if I call wait here? Does the alert dialog still appear and prevent the user from performing any other action?

void waitForService() {
    openConnectionToUploadQueue();
    if(answersQueue.getCount(objInterviewQuestion.getQid()) <= 0){
        answersQueue.close();
        return;
    }
    if(!answersQueue.isInterviewUploadServiceRunning()) {
        answersQueue.startInterviewUploadService();
    }
    AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
    builder.setTitle(getString(R.string.auto_submit_alert_title));
    builder.setCancelable(false);
    builder.setMessage(R.string.uploading_pending_answers);
    AlertDialog waitForServiceDialog = builder.create();
    waitForServiceDialog.show();
    while (answersQueue.getCount(objInterviewQuestion.getQid()) > 0) {
         do nothing and keep loop running till answersQueue is empty
    }
    waitForServiceDialog.dismiss();
}

You should never block the UI thread. When you hold the UI thread for too long, a dialog box appears that says XXX is not responding and asks the user to terminate your application.

Instead, you

should use callback-style calls, and when the service starts, you receive a method call from the callback to close the dialog box.

Edit:

As mentioned earlier, you need to implement BroadcastReceiver

This is a demo project that you can use as an example of how to create and use BroadcastReceiver.

https://github.com/cyfung/ActivityRecognitionSample