[SOLVED] Listener to detect whether a view is at the front?

Listener to detect whether a view is at the front?

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?

Solution

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
            }
          }
        });