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

我检测加载事件的方法不是检测滚动,而是监听最后一个视图是否附加。如果附加了最后一个视图,我认为这是加载更多内容的时机。

class MyListener implements RecyclerView.OnChildAttachStateChangeListener {
    RecyclerView mRecyclerView;

    MyListener(RecyclerView view) {
        mRecyclerView = view;
    }

    @Override
    public void onChildViewAttachedToWindow(View view) {

    RecyclerView.Adapter adapter = mRecyclerView.getAdapter();
    RecyclerView.LayoutManager mgr = mRecyclerView.getLayoutManager();
    int adapterPosition = mgr.getPosition(view);

    if (adapterPosition == adapter.getItemCount() - 1) {
        // last view was attached
        loadMoreContent();
    }

    @Override
    public void onChildViewDetachedFromWindow(View view) {}
}

其他回答

我的答案是一个改良版的努尔。我从一个ListView,在那里我有EndlessScrollListener(你可以很容易地在SO上找到许多答案)到一个RecyclerView,所以我想要一个endlessrecyscrolllistener轻松地更新我过去的监听器。

下面是代码,希望能有所帮助:

public abstract class EndlessScrollRecyclListener extends RecyclerView.OnScrollListener
{
    // The total number of items in the dataset after the last load
    private int previousTotalItemCount = 0;
    private boolean loading = true;
    private int visibleThreshold = 5;
    int firstVisibleItem, visibleItemCount, totalItemCount;
    private int startingPageIndex = 0;
    private int currentPage = 0;

    @Override
    public void onScrolled(RecyclerView mRecyclerView, int dx, int dy)
    {
        super.onScrolled(mRecyclerView, dx, dy);
        LinearLayoutManager mLayoutManager = (LinearLayoutManager) mRecyclerView
                .getLayoutManager();

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

    public void onScroll(int firstVisibleItem, int visibleItemCount, int totalItemCount)
    {
        // If the total item count is zero and the previous isn't, assume the
        // list is invalidated and should be reset back to initial state
        if (totalItemCount < previousTotalItemCount)
        {
            this.currentPage = this.startingPageIndex;
            this.previousTotalItemCount = totalItemCount;
            if (totalItemCount == 0)
            {
                this.loading = true;
            }
        }
        // If it’s still loading, we check to see if the dataset count has
        // changed, if so we conclude it has finished loading and update the current page
        // number and total item count.
        if (loading && (totalItemCount > previousTotalItemCount))
        {
            loading = false;
            previousTotalItemCount = totalItemCount;
            currentPage++;
        }

        // If it isn’t currently loading, we check to see if we have breached
        // the visibleThreshold and need to reload more data.
        // If we do need to reload some more data, we execute onLoadMore to fetch the data.
        if (!loading && (totalItemCount - visibleItemCount) <= (firstVisibleItem +
                visibleThreshold))
        {
            onLoadMore(currentPage + 1, totalItemCount);
            loading = true;
        }
    }

    // Defines the process for actually loading more data based on page
    public abstract void onLoadMore(int page, int totalItemsCount);

}

也可以在没有滚动侦听器的情况下实现,只使用数据模型的纯逻辑。滚动视图需要按位置获取项目以及最大项目计数。模型可以具有后台逻辑,以块的形式获取所需的项,而不是一个一个地获取,并在后台线程中执行此操作,在数据准备就绪时通知视图。

这种方法允许获取队列优先选择最近请求的(所以当前可见)项而不是旧的(很可能已经滚动了)提交,控制使用的并行线程的数量等等。这个方法的完整源代码(演示应用程序和可重用库)可以在这里找到。

正如约翰·T所建议的。只需使用下面的代码块,真的很简短,美观简单:D

public void loadMoreOnRecyclerView() {
    mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
        @Override
        public void onScrolled(@NonNull @NotNull RecyclerView recyclerView, int dx, int dy) {
            super.onScrolled(recyclerView, dx, dy);
            if (!recyclerView.canScrollVertically(1) && dy != 0) {
                //Load more items here
            }
        }
    });
}

你可以跟随我的回购来了解它的工作方式。

https://github.com/Nghien-Nghien/PokeAPI-Java/blob/0d8d69d348e068911b883f0ae7791d904cc75cb5/app/src/main/java/com/example/pokemonapi/MainActivity.java

关于应用程序的描述信息如下:https://github.com/skydoves/Pokedex#readme

我有一个关于如何使用RecyclerView进行分页的非常详细的示例。在高层次,我有一个设置PAGE_SIZE,让我们说30。所以我请求30个项目,如果我得到30个,我就请求下一页。如果我得到的条目少于30个,我就标记一个变量来指示已经到达最后一页,然后停止请求更多的页面。看看吧,告诉我你的想法。

https://medium.com/@etiennelawlor/pagination-with-recyclerview-1cb7e66a502b

有一个方法public void setOnScrollListener (RecyclerView。OnScrollListener监听器)在https://developer.android.com/reference/android/support/v7/widget/RecyclerView.html#setOnScrollListener%28android.support.v7.widget.RecyclerView.OnScrollListener%29。使用这个

编辑:

在onScrollListener中重写onScrollStateChanged方法并执行此操作

            boolean loadMore = firstVisibleItem + visibleItemCount >= totalItemCount;

            //loading is used to see if its already loading, you have to manually manipulate this boolean variable
            if (loadMore && !loading) {
                 //end of list reached
            }