code: private int[] gotExistedPadding() {
          int[] ret = new int[4];
          ret[0] = getPaddingLeft();
          if (0 == ret[0]) {
              ret[0] = cornerSizeLeftTop > cornerSizeLeftBottom ? cornerSizeLeftTop : cornerSizeLeftBottom;
          }
  
          ret[1] = getPaddingTop();
          if (0 == ret[1]) {
              ret[1] = cornerSizeLeftTop > cornerSizeRightTop ? cornerSizeLeftTop : cornerSizeRightTop;
          }
  
          ret[2] = getPaddingRight();
          if (0 == ret[2]) {
              ret[2] = cornerSizeRightTop > cornerSizeRightBottom ? cornerSizeRightTop : cornerSizeRightBottom;
          }
  
          ret[3] = getPaddingBottom();
          if (0 == ret[3]) {
              ret[3] = cornerSizeLeftBottom > cornerSizeRightBottom ? cornerSizeLeftBottom : cornerSizeRightBottom;
          }
          return ret;
      }
docs: 获取已设置了的padding值