我想把ListView改为RecyclerView。我想在RecyclerView中使用OnScrollListener的onScroll来确定用户是否滚动到列表的末尾。

我如何知道用户是否滚动到列表的末尾以便我可以从REST服务获取新数据?


当前回答

虽然这个问题有很多答案,但我还是想分享一下我们创建无尽列表视图的经验。我们最近实现了自定义Carousel LayoutManager,可以在循环中无限滚动列表以及到某个点。下面是GitHub上的详细描述。

我建议您看看这篇关于创建自定义LayoutManagers的简短但有价值的建议:http://cases.azoft.com/create-custom-layoutmanager-android/

其他回答

感谢@Kushal,这是我实现它的方式

private boolean loading = true;
int pastVisiblesItems, visibleItemCount, totalItemCount;

mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
    @Override
    public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
        if (dy > 0) { //check for scroll down
            visibleItemCount = mLayoutManager.getChildCount();
            totalItemCount = mLayoutManager.getItemCount();
            pastVisiblesItems = mLayoutManager.findFirstVisibleItemPosition();

            if (loading) {
                if ((visibleItemCount + pastVisiblesItems) >= totalItemCount) {
                    loading = false;
                    Log.v("...", "Last Item Wow !");
                    // Do pagination.. i.e. fetch new data

                    loading = true;
                }
            }
        }
    }
});

别忘了加上

LinearLayoutManager mLayoutManager;
mLayoutManager = new LinearLayoutManager(this);
mRecyclerView.setLayoutManager(mLayoutManager);

对我来说,这很简单:

     private boolean mLoading = false;

     mList.setOnScrollListener(new RecyclerView.OnScrollListener() {

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

            int totalItem = mLinearLayoutManager.getItemCount();
            int lastVisibleItem = mLinearLayoutManager.findLastVisibleItemPosition();

            if (!mLoading && lastVisibleItem == totalItem - 1) {
                mLoading = true;
                // Scrolled to bottom. Do something here.
                mLoading = false;
            }
        }
    });

小心异步作业:mLoading必须在异步作业结束时更改。希望对大家有所帮助!

我刚试了一下:

    final LinearLayoutManager rvLayoutManager = new LinearLayoutManager(this);
    rvMovieList = (RecyclerView) findViewById(R.id.rvMovieList);
    rvMovieList.setLayoutManager(rvLayoutManager);
    adapter = new MovieRecyclerAdapter(this, movies);
    rvMovieList.setAdapter(adapter);
    adapter.notifyDataSetChanged();

    rvMovieList.addOnScrollListener(new OnScrollListener() {
        boolean loading = true;
        int pastVisiblesItems, visibleItemCount, totalItemCount;
        @Override
        public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
            super.onScrolled(recyclerView, dx, dy);

            visibleItemCount = rvLayoutManager.getChildCount();
            totalItemCount = rvLayoutManager.getItemCount();
            pastVisiblesItems = rvLayoutManager.findFirstVisibleItemPosition();

            int lastitem = visibleItemCount + pastVisiblesItems;

            if ( lastitem == totalItemCount
                    && page < total_pages
                    && !keyword.equals("") ) {
                // hit bottom ..

                String strnext;
                if (page == total_pages - 1) {
                    int last = total_results - (page * 20);
                    strnext = String.format(getResources().getString(R.string.next), last);
                } else {
                    strnext = String.format(getResources().getString(R.string.next), 20);
                }
                btNext.setText(strnext);
                btNext.setVisibility(View.VISIBLE);
            } else {
                btNext.setVisibility(View.INVISIBLE);
            }

            if(pastVisiblesItems == 0 &&  page > 1){
                // hit top
                btPrev.setVisibility(View.VISIBLE);
            } else {
                btPrev.setVisibility(View.INVISIBLE);
            }
        }
    });

我搞不清楚在哪里加载真或假,所以我试图删除它,这段代码工作如我所料。

做这些变量。

private int previousTotal = 0;
private boolean loading = true;
private int visibleThreshold = 5;
int firstVisibleItem, visibleItemCount, totalItemCount;

设置为滚动回收视图。

mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {

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

        visibleItemCount = mRecyclerView.getChildCount();
        totalItemCount = mLayoutManager.getItemCount();
        firstVisibleItem = mLayoutManager.findFirstVisibleItemPosition();

        if (loading) {
            if (totalItemCount > previousTotal) {
                loading = false;
                previousTotal = totalItemCount;
            }
        }
        if (!loading && (totalItemCount - visibleItemCount) 
            <= (firstVisibleItem + visibleThreshold)) {
            // End has been reached

            Log.i("Yaeye!", "end called");

            // Do something

            loading = true;
        }
    }
});

注意:确保你使用LinearLayoutManager作为RecyclerView的布局管理器。

LinearLayoutManager mLayoutManager;
mLayoutManager = new LinearLayoutManager(this);
mRecyclerView.setLayoutManager(mLayoutManager);

对于网格来说

GridLayoutManager mLayoutManager;
mLayoutManager = new GridLayoutManager(getActivity(), spanCount);
mRecyclerView.setLayoutManager(mLayoutManager);

有乐趣与你无尽的卷轴!!^ ^。

更新:mRecyclerView.setOnScrollListener()已弃用,只需替换为mRecyclerView.addOnScrollListener(),警告将消失!你可以从这个SO问题中读到更多。

由于Android现在正式支持Kotlin,这里是相同的更新-

使OnScrollListener

class OnScrollListener(val layoutManager: LinearLayoutManager, val adapter: RecyclerView.Adapter<RecyclerAdapter.ViewHolder>, val dataList: MutableList<Int>) : RecyclerView.OnScrollListener() {
    var previousTotal = 0
    var loading = true
    val visibleThreshold = 10
    var firstVisibleItem = 0
    var visibleItemCount = 0
    var totalItemCount = 0

    override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
        super.onScrolled(recyclerView, dx, dy)

        visibleItemCount = recyclerView.childCount
        totalItemCount = layoutManager.itemCount
        firstVisibleItem = layoutManager.findFirstVisibleItemPosition()

        if (loading) {
            if (totalItemCount > previousTotal) {
                loading = false
                previousTotal = totalItemCount
            }
        }

        if (!loading && (totalItemCount - visibleItemCount) <= (firstVisibleItem + visibleThreshold)) {
            val initialSize = dataList.size
            updateDataList(dataList)
            val updatedSize = dataList.size
            recyclerView.post { adapter.notifyItemRangeInserted(initialSize, updatedSize) }
            loading = true
        }
    }
}

然后像这样把它添加到你的RecyclerView中

recyclerView.addOnScrollListener(OnScrollListener(layoutManager, adapter, dataList))

要获得完整的代码示例,请参阅Github repo。

虽然这个问题有很多答案,但我还是想分享一下我们创建无尽列表视图的经验。我们最近实现了自定义Carousel LayoutManager,可以在循环中无限滚动列表以及到某个点。下面是GitHub上的详细描述。

我建议您看看这篇关于创建自定义LayoutManagers的简短但有价值的建议:http://cases.azoft.com/create-custom-layoutmanager-android/