code: private static void notifyDrawable(Drawable drawable, final boolean isDisplayed) {
          if (drawable instanceof RecyclingBitmapDrawable) {
              // The drawable is a CountingBitmapDrawable, so notify it
              ((RecyclingBitmapDrawable) drawable).setIsDisplayed(isDisplayed);
          } else if (drawable instanceof LayerDrawable) {
              // The drawable is a LayerDrawable, so recurse on each layer
              LayerDrawable layerDrawable = (LayerDrawable) drawable;
              for (int i = 0, z = layerDrawable.getNumberOfLayers(); i < z; i++) {
                  notifyDrawable(layerDrawable.getDrawable(i), isDisplayed);
              }
          }
      }
docs: Notifies the drawable that it's displayed state has changed.
  
  @param drawable
  @param isDisplayed