code: public Drawable findDrawableByLayerId(int id) {
          final ChildDrawable[] layers = mLayerState.mChildren;
          for (int i = mLayerState.mNum - 1; i >= 0; i--) {
              if (layers[i].mId == id) {
                  return layers[i].mDrawable;
              }
          }
  
          return null;
      }
docs: Looks for a layer with the given ID and returns its {@link Drawable}.
  <p/>
  If multiple layers are found for the given ID, returns the {@link Drawable} for the matching
  layer at the highest index.
  
  @param id The layer ID to search for.
  @return The {@link Drawable} for the highest-indexed layer that has the given ID, or null if
  not found.