clear Focus
Called when this view wants to give up focus. If focus is cleared onFocusChanged(boolean, int, android.graphics.Rect) is called.
Note: When not in touch-mode, the framework will try to give focus to the first focusable View from the top after focus is cleared. Hence, if this View is the first from the top that can take focus, then all callbacks related to clearing focus will be invoked after which the framework will give focus to this view.