docs: public void onPrepareMenu(){
          if(mGroupChanged || mMenuDataChanged){
              mToolbar.getViewTreeObserver().addOnGlobalLayoutListener(mOnGlobalLayoutListener);
  
              Menu menu = mToolbar.getMenu();
              for(int i = 0, count = menu.size(); i < count; i++){
                  MenuItem item = menu.getItem(i);
                  item.setVisible(item.getGroupId() == mCurrentGroup || item.getGroupId() == 0);
              }
  
              mMenuDataChanged = false;
          }
      }