CountdownTimer in a separate thread with looper

Question

I am trying to implement a countdown to warn users when they are exiting an area. To do this, I am attempting to use a CountdownTimer in a JobIntentService; however, this means the CountdownTimer is in a thread without a looper causing an exception to be thrown. java.lang.RuntimeException: Can't create handler inside thread Thread[AsyncTask #1,5,main] that has not called Looper.prepare()

I have found this Question on a CountdownTimer in its own thread with looper, but the answer there is 6-7 years old and I want to be using the best practices for threading and handlers.

If anyone could give a little insight into how to do this in a cleaner way, it would definitely be appreciated.

Answer 1

Always create handler with the use of Looper.

1) Creater UI handler to update the UI

Handler mainThreadhandler = new Handler(context.getMainLooper());
mainThreadhandler.post(new Runnable(){
   public void run(){
    // UI work
   }
});

2) Create Thread handler, to run the background task.

HandlerThread bgThread = new HandlerThread("MyHandlerThread");
bgThread.start();
Handler bgHandler = new Handler(bgThread.getLooper());
bgHandler.post(new Runnable(){
   public void run(){
    // background work
   }
});

Don't forget to cleanup while finishing the activity.

@Override
public void onDestroy() {
  bgHandler.getLooper().quit();
  super.onDestroy();
}