code: public static void setBackgroundResource(EfficientCacheView cacheView, int viewId,
              @DrawableRes int resid) {
          View view = cacheView.findViewByIdEfficient(viewId);
          if (view != null) {
              view.setBackgroundResource(resid);
          }
      }
docs: Equivalent to calling View.setBackgroundResource
  
  @param cacheView The cache of views to get the view from
  @param viewId    The id of the view whose background should change
  @param resid     The new background resource for the view