code: public void setPaddingRelative(int start, int top, int end, int bottom) {
          final LayerState layerState = mLayerState;
          layerState.mPaddingStart = start;
          layerState.mPaddingTop = top;
          layerState.mPaddingEnd = end;
          layerState.mPaddingBottom = bottom;
  
          // Clear absolute padding values.
          layerState.mPaddingLeft = -1;
          layerState.mPaddingRight = -1;
      }
docs: Sets the relative padding.
  <p/>
  If padding in a dimension is specified as {@code -1}, the resolved padding will use the value
  computed according to the padding mode (see {@link #setPaddingMode(int)}).
  <p/>
  Calling this method clears any absolute padding values previously set using {@link
  #setPadding(int, int, int, int)}.
  
  @param start  the start padding in pixels, or -1 to use computed padding
  @param top    the top padding in pixels, or -1 to use computed padding
  @param end    the end padding in pixels, or -1 to use computed padding
  @param bottom the bottom padding in pixels, or -1 to use computed padding
  @attr ref android.R.styleable#LayerDrawable_paddingStart
  @attr ref android.R.styleable#LayerDrawable_paddingTop
  @attr ref android.R.styleable#LayerDrawable_paddingEnd
  @attr ref android.R.styleable#LayerDrawable_paddingBottom
  @see #setPadding(int, int, int, int)