code: public void setPadding(int left, int top, int right, int bottom) {
          if ((left | top | right | bottom) == 0) {
              mState.mPadding = null;
          } else {
              if (mState.mPadding == null) {
                  mState.mPadding = new Rect();
              }
              mState.mPadding.set(left, top, right, bottom);
          }
          invalidateSelf();
      }
docs: Sets padding for the shape.
  
  @param left   padding for the left side (in pixels)
  @param top    padding for the top (in pixels)
  @param right  padding for the right side (in pixels)
  @param bottom padding for the bottom (in pixels)