RecycleView滑动监听

很多app的需求就有用RecycleView来实现，但是一般我们是从后端请求到RecycleView的数据，如何动态请求呢，即RecycleView下滑到底部时继续请求数据

private fun freshRecycleView() {
        var isSliding: Boolean = false
        rv.addOnScrollListener(object : RecyclerView.OnScrollListener() {
            override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
                super.onScrolled(recyclerView, dx, dy)
                //dx为横向滚动 dy为竖向滚动
                //如果为竖向滚动,则isSliding属性为true，横向滚动则为false
                isSliding = dy > 0
            }
            override fun onScrollStateChanged(recyclerView: RecyclerView, newState: Int) {
                super.onScrollStateChanged(recyclerView, newState)
                //manager必须为LinearLayoutManager
                val manager: LinearLayoutManager = rv.layoutManager as LinearLayoutManager
                //newState是RecycleView的状态 如果它的状态为没有滚动时
                if (newState == RecyclerView.SCROLL_STATE_IDLE) {
                    //获取最后一个完全显示的ItemPosition
                    val lastVisibleItem = manager.findLastCompletelyVisibleItemPosition()
                    //获取目前的item的数量
                    val totalItem = manager.itemCount
                    if (lastVisibleItem == (totalItem - 1)) {
                        //当滑动到最后一个时，加载更多数据
                        loadMoreData()
                    }
                }
            }
        })
    }

第一个函数onScrolled()是监听RecycleView的滚动方向

第二个函数onScrollStateChanged()是监听RecycleView滑动状态的改变