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

@erdna请参考我下面的代码。也许它会对你有帮助。

     int firstVisibleItem, visibleItemCount, totalItemCount;
   recyclerView.setOnScrollListener(new RecyclerView.OnScrollListener() {

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

            visibleItemCount = layoutManager.getChildCount();
            totalItemCount = layoutManager.getItemCount();
            firstVisibleItem = layoutManager.findFirstVisibleItemPosition();
            Log.e("firstVisibleItem", firstVisibleItem + "");
            Log.e("visibleItemCount", visibleItemCount + "");
            Log.e("totalItemCount", totalItemCount + "");

            if (page != total_page_index) {
                if (loading) {
                    if ((visibleItemCount + firstVisibleItem) >= totalItemCount) {
                        Log.e("page", String.valueOf(page));
                        page=page+1;
                        new GetSummary().execute(String.valueOf(page), "");
                        loading = false;
                    }
                }
            }

        }


    });

其他回答

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
            }

我已经创建LoadMoreRecyclerView使用Abdulaziz Noor回答

LoadMoreRecyclerView

public class LoadMoreRecyclerView extends RecyclerView  {

    private boolean loading = true;
    int pastVisiblesItems, visibleItemCount, totalItemCount;
    //WrapperLinearLayout is for handling crash in RecyclerView
    private WrapperLinearLayout mLayoutManager;
    private Context mContext;
    private OnLoadMoreListener onLoadMoreListener;

    public LoadMoreRecyclerView(Context context) {
        super(context);
        mContext = context;
        init();
    }

    public LoadMoreRecyclerView(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        mContext = context;
        init();
    }

    public LoadMoreRecyclerView(Context context, @Nullable AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        mContext = context;
        init();
    }

    private void init(){
        mLayoutManager = new WrapperLinearLayout(mContext,LinearLayoutManager.VERTICAL,false);
        this.setLayoutManager(mLayoutManager);
        this.setItemAnimator(new DefaultItemAnimator());
        this.setHasFixedSize(true);
    }

    @Override
    public void onScrolled(int dx, int dy) {
        super.onScrolled(dx, 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("...", "Call Load More !");
                    if(onLoadMoreListener != null){
                        onLoadMoreListener.onLoadMore();
                    }
                    //Do pagination.. i.e. fetch new data
                }
            }
        }
    }

    @Override
    public void onScrollStateChanged(int state) {
        super.onScrollStateChanged(state);
    }

    public void onLoadMoreCompleted(){
        loading = true;
    }

    public void setMoreLoading(boolean moreLoading){
        loading = moreLoading;
    }

    public void setOnLoadMoreListener(OnLoadMoreListener onLoadMoreListener) {
        this.onLoadMoreListener = onLoadMoreListener;
    }
}

WrapperLinearLayout

public class WrapperLinearLayout extends LinearLayoutManager
{
    public WrapperLinearLayout(Context context, int orientation, boolean reverseLayout) {
        super(context, orientation, reverseLayout);
    }

    @Override
    public void onLayoutChildren(RecyclerView.Recycler recycler, RecyclerView.State state) {
        try {
            super.onLayoutChildren(recycler, state);
        } catch (IndexOutOfBoundsException e) {
            Log.e("probe", "meet a IOOBE in RecyclerView");
        }
    }
}

//在xml中添加

<your.package.LoadMoreRecyclerView
    android:id="@+id/recycler_view"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
</your.package.LoadMoreRecyclerView>

OnCreate或onViewCreated

mLoadMoreRecyclerView = (LoadMoreRecyclerView) view.findViewById(R.id.recycler_view);
mLoadMoreRecyclerView.setOnLoadMoreListener(new OnLoadMoreListener() {
            @Override
            public void onLoadMore() {
                callYourService(StartIndex);
            }
        });

callYourService

private void callYourService(){
    //callyour Service and get response in any List

    List<AnyModelClass> newDataFromServer = getDataFromServerService();
    //Enable Load More
    mLoadMoreRecyclerView.onLoadMoreCompleted();

    if(newDataFromServer != null && newDataFromServer.size() > 0){
            StartIndex += newDataFromServer.size();

            if (newDataFromServer.size() < Integer.valueOf(MAX_ROWS)) {
                    //StopLoading..
                   mLoadMoreRecyclerView.setMoreLoading(false);
            }
    }
    else{
            mLoadMoreRecyclerView.setMoreLoading(false);
            mAdapter.notifyDataSetChanged();
    }
}

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);

}

没有重复调用,但你滚动。fetchData只会在您位于列表的末尾并且有更多数据要获取时调用

关于我的代码: 1.fetchData()每次调用取10个项。 2.isScrolling是一个类成员变量 3.previousTotalCount也是类成员。它存储以前访问过的最后一个项目

recyclerView.addOnScrollListener(object : RecyclerView.OnScrollListener() {
            override fun onScrollStateChanged(recyclerView: RecyclerView, newState: Int) {
                super.onScrollStateChanged(recyclerView, newState)
                if (newState == AbsListView.OnScrollListener.SCROLL_STATE_TOUCH_SCROLL) {
                    isScrolling = true
                }
            }

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

                val visibleItemCount = layoutManager.childCount
                val totalItemCount = layoutManager.itemCount
                val scrolledOutItems = layoutManager.findFirstVisibleItemPosition()


                if (isScrolling && (visibleItemCount + scrolledOutItems == totalItemCount)
                    && (visibleItemCount + scrolledOutItems != previousTotalCount)) {
                    previousTotalCount = totalItemCount              
                    isScrolling = false
                    fetchData()  //fetches 10 new items from Firestore
                    pagingProgressBar.visibility = View.VISIBLE
                }
            }
        })

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) {}
}