Listener to detect whether a view is at the front?

Question

I have RecyclerView and, in some cases, I show another view on top of it - ProgressDialog, AlertDialog or DialogFragment.

Is there some way to notify me about cases when my RecyclerView is at front or another view is above it now?

I tried to add onFocusChangeListener() to my RecyclerView, but no luck.

PS. Definitely, I can in my RecyclerView create some method isOnFront(boolean onFront) and in all my other views call it, but maybe there is some more elegance way?

Answer 1

ProgressDialog, AlertDialog and DialogFragment would lay their content on the Window, not to your activity's/fragment's view hierarchy. Which means, that as soon as either of them is shown, the focus of Window is changed. Hence, you can make use of ViewTreeObserver#addOnWindowFocusChangeListener() API:

    contentView.getViewTreeObserver().addOnWindowFocusChangeListener(
        new ViewTreeObserver.OnWindowFocusChangeListener() {
          @Override public void onWindowFocusChanged(boolean hasFocus) {
            // Remove observer when no longer needed
            // contentView.getViewTreeObserver().removeOnWindowFocusChangeListener(this);

            if (hasFocus) {
              // Your view hierarchy is in the front
            } else {
              // There is some other view on top of your view hierarchy,
              // which resulted in losing the focus of window
            }
          }
        });