How to know when an activity finishes a layout pass?

Question

I have a background thread that updates the UI of my activity, after the onCreate(). It can be adding layouts, or changing the size of others.

I simply

Answer 1

You can use the ViewTreeObserver.OnPreDrawListener

per the docs at https://developer.android.com/reference/android/view/ViewTreeObserver.OnPreDrawListener

At this point, all views in the tree have been measured and given a frame.

Only if a view in your tree requests another layout pass, will any layout bounds change. You could also use similar technique using the ViewTreeObserver.OnDrawListener to get the callback even later

myView.getViewTreeObserver().addOnPreDrawListener(
    new ViewTreeObserver.OnPreDrawListener() {
        @Override
        public boolean onPreDraw() {
            myView.getViewTreeObserver().removeOnPreDrawListener(this);
            // view is measured and laid out
        });