如何检测RecyclerView何时滚动到最顶部位置

Question

我上面有 RecyclerView，我有一个高度大于 255 px 的 AppBarLayout。当用户滚动 RecyclerView 时，AppBarLayout 出现 fling 问题。为了避免这种情况，我决定手动扩展 AppBarLayout。我的 RecyclerView 由 GridLayoutManager 组成，跨度为 3。我使用下面的代码来监听 RecyclerView 顶部到达

recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
    @Override
    public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
        super.onScrollStateChanged(recyclerView, newState);
        if (newState == RecyclerView.SCROLL_STATE_IDLE) {
            int firstVisiblePosition = ((LinearLayoutManager)recyclerView.getLayoutManager()).findFirstCompletelyVisibleItemPosition();
            if (firstVisiblePosition == 0) {
                appBarLayout.setExpanded(true, true);
            }
        }
    }
});

Answer 1

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

            int firstVisibleItem = gridLayoutManager.findFirstCompletelyVisibleItemPosition();

            if(firstVisibleItem == 0){
                // your code
            }
        }
    });

Answer 2

这个答案会对你有帮助。真心的你

recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
        @Override
        public void onScrollStateChanged(@NonNull RecyclerView recyclerView, int newState) {

            super.onScrollStateChanged(recyclerView, newState);
        }

        @Override
        public void onScrolled(@NonNull RecyclerView recyclerView, int dx, int dy) {
            super.onScrolled(recyclerView, dx, dy);

            totalItemCount = layoutManager.getItemCount();
            visibleItemCount = layoutManager.getChildCount();
            pastVisiblesItems = layoutManager.findFirstVisibleItemPosition();
            if ((visibleItemCount + pastVisiblesItems) >= totalItemCount ) {

                Log.d(TAG, "scroll down");



            }
            else{
                Log.d(TAG, "scroll up");
            }
        }
    });

Answer 3

我找到了一个绝妙的解决方案这里。你可以在你的内部实现它

RecyclerView.OnScrollListener

像这样：

binding.recyclerView.addOnScrollListener(object : RecyclerView.OnScrollListener() {
    override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
        super.onScrolled(recyclerView, dx, dy)

        if (!recyclerView.canScrollVertically(-1)) {
            Log.d(TAG, "THE TOP")
        } else {
            Log.d(TAG, "NOT TOP")
        }
    }
})