code: public DrawerBuilder withFooter(@LayoutRes int footerViewRes) {
          if (mActivity == null) {
              throw new RuntimeException("please pass an activity first to use this call");
          }
  
          if (footerViewRes != -1) {
              //i know there should be a root, bit i got none here
              this.mFooterView = mActivity.getLayoutInflater().inflate(footerViewRes, null, false);
          }
  
          return this;
      }
docs: Add a footer to the DrawerBuilder ListView defined by a resource.
  
  @param footerViewRes
  @return