code: public static int getCenterYChildPosition(RecyclerView recyclerView) {
          int childCount = recyclerView.getChildCount();
          for (int i = 0; i < childCount; i++) {
              View child = recyclerView.getChildAt(i);
              if (isChildInCenterY(recyclerView, child)) {
                  return recyclerView.getChildAdapterPosition(child);
              }
          }
          return childCount;
      }
docs: Get position of center child in Y Axes