Toast if a component gains focus

Question

I want to display a Toast if the map view gains focus. What I’ve been able to do so far is:

        mapView.setOnFocusChangeListener(new View.OnFocusChangeListener() {
        @Override
        public void onFocusChange(View v, boolean hasFocus) {
            if (hasFocus) {
                Toast.makeText(getApplicationContext(), "Tem o foco", Toast.LENGTH_SHORT).show();
            }
        }
    });

But apparently, just scrolling the screen does not give the focus to the component. How to proceed?