Android - How to tell when a specific view has been rendered?

Question

I have a regular button that I want to display a timer on. So imagine the text of the button changes every second as a countdown timer. However, I need this timer to only st

Answer 1

OnGlobalLayoutListener() is the right place to go. It's guaranteed that it will be called when your button has been layed out ("fully rendered and ready to go on the screen"). For example, in onCreate() you could do:

btn = (Button) findViewById(R.id.bn);   
btn.getViewTreeObserver().addOnGlobalLayoutListener(new OnGlobalLayoutListener() {

    @Override
    public void onGlobalLayout() {
        new AsyncTaskTimer.execute();
        // prevent the listener to be called more than once
        btn.getViewTreeObserver().removeOnGlobalLayoutListener(this);
    }
});