recycleview 的名字是FoodsNameRecycle

 FoodsNameRecycle.setOnScrollListener(new RecyclerView.OnScrollListener() {
            @Override
            public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
                super.onScrolled(recyclerView, dx, dy);
            }

            @Override
            public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
                super.onScrollStateChanged(recyclerView, newState);
                RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();
                //判断是当前layoutManager是否为LinearLayoutManager
                // 只有LinearLayoutManager才有查找第一个和最后一个可见view位置的方法
                if (layoutManager instanceof LinearLayoutManager) {
                    LinearLayoutManager linearManager = (LinearLayoutManager) layoutManager;
                    //获取最后一个可见view的位置
                    int lastItemPosition = linearManager.findLastVisibleItemPosition();
                    //获取第一个可见view的位置
                    int firstItemPosition = linearManager.findFirstVisibleItemPosition();
                    if (foodsArrayList.get(firstItemPosition) instanceof Foods) {
                        int foodTypePosion = ((Foods) foodsArrayList.get(firstItemPosition)).getFood_stc_posion();
                        FoodsTypeListview.getChildAt(foodTypePosion).setBackgroundResource(R.drawable.choose_item_selected);
                    }
                    System.out.println(lastItemPosition + " " + firstItemPosition);
                }
            }
        });