code: public void showEdgeShadow(boolean left, boolean top, boolean right, boolean bottom) {
          if (SDK_LOLLIPOP) {
              //((OptRoundRectDrawable) getBackground()).showCorner(leftTop, rightTop, leftBottom, rightBottom);
          } else {
              ((OptRoundRectDrawableWithShadow) getBackground()).showEdgeShadow(left, top, right, bottom);
          }
      }
docs: show Edge Shadow