CODEWITHSUNDEEP
androidmultithreadingfirebasefirebase-realtime-databaseexecutorservice
Tord Larsen
Tord Larsen

Reputation: 2840

Where will Firebase onDataChange() run in this example?

I know the onDataChange() in Firebase for let say addListenerForSingleValueEvent is running on Android Main Ui thread.

I Wanted to understand what will happen if I run this code inside the ExecutorService:

runInBackground(new Runnable() {
@Override
public void run() {
    ref.child("SOME_KEY")
            .addListenerForSingleValueEvent
                    (new ValueEventListener() {
                         @Override
                         public void onDataChange(final DataSnapshot dataSnapshot) {
                             //.. do some work on Ui Thread or not??
                         }

                         @Override
                         public void onCancelled(DatabaseError databaseError) {
                             notificationRunning = false;
                         }
                     }
                    );
}
});
}

Will the onDataChange() still run on the Main Ui Thread in Android? And here´s the ExecutorService runner

/**
 * Submits request to be executed in background.
 * Threads submitted will be executed synchronously.
 *
 * @param runnable
 */
private void runInBackground(final Runnable runnable) {
    mBackgroundExecutor.submit(new Runnable() {
        @Override
        public void run() {
            try {
                runnable.run();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    });
}

And the ExecutorService

mBackgroundExecutor = Executors
        .newSingleThreadExecutor(new ThreadFactory() {
            @Override
            public Thread newThread(Runnable runnable) {
                Thread thread = new Thread(runnable,
                        "Background executor service for OneSignal");
                thread.setPriority(Thread.MIN_PRIORITY);
                thread.setDaemon(true);
                return thread;
            }
        });

Upvotes: 0

Views: 500

Answers (1)

Bob Snyder
Bob Snyder

Reputation: 38289

The listener callbacks always run on the main/UI thread. The thread that was used to add the listener does not affect the callback thread. You can confirm this by adding a log statement to your callback that outputs the thread name:

Log.d(TAG, "onDataChange: Thread=" + Thread.currentThread().getName());

Upvotes: 1

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