Basics: Running code in main thread

Issue

Given that posting a task with post() puts the Runnable in a queue, is there any difference between

protected void onCreate(Bundle savedInstanceState) {
    Log.d("UI thread", "Do something");
}    

and

protected void onCreate(Bundle savedInstanceState) {
    new Handler(Looper.getMainLooper()).post(new Runnable() {
        @Override
        public void run() {
            Log.d("UI thread", "Do something");
        }
    });
}

?

In both cases, there should only be one thread running and no concurrency happening - right?

Then what's the benefit in creating a handler that attaches to the UI thread and running tasks on it?

Solution

The timing is different. In the first snippet the code is executed as part of the onCreate execution so it is guaranteed to finish before onCreate returns, in the second snippet, it is executed some time later (maybe after several other callbacks).

Answered By - Henry