code: private void findScrollView(ViewGroup viewGroup) {
          scrollChild = viewGroup;
          if (viewGroup.getChildCount() > 0) {
              int count = viewGroup.getChildCount();
              View child;
              for (int i = 0; i < count; i++) {
                  child = viewGroup.getChildAt(i);
                  if (child instanceof AbsListView || child instanceof ScrollView || child instanceof ViewPager || child instanceof WebView) {
                      scrollChild = child;
                      return;
                  }
              }
          }
      }
docs: Find out the scrollable child view from a ViewGroup.
  
  @param viewGroup