code: private Drawable createPressedBackgroundDrawable() {
          Drawable drawable = createBackgroundDrawable(getColor());
          Drawable hoverDrawable = createBackgroundDrawable(getPressedColor());
          return new LayerDrawable(new Drawable[]{drawable, hoverDrawable});
      }
docs: Creates and returns a drawable, which can be used as the floating action button's background,
  when it is pressed.
  
  @return The drawable, which has been created, as an instance of the class {@link Drawable}