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

我使用了recyclerview。adapter的onBindViewHolder方法。

适配器:

public interface OnViewHolderListener {
    void onRequestedLastItem();
}

@Override
public void onBindViewHolder(ViewHolder holder, int position) {

    ...

    if (position == getItemCount() - 1) onViewHolderListener.onRequestedLastItem();
}

片段(或活动):

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    contentView = inflater.inflate(R.layout.comments_list, container, false);
    recyclerView = (RecyclerView) mContentView.findViewById(R.id.my_recycler_view);
    adapter = new Adapter();
    recyclerView.setAdapter(adapter);

    ...

    adapter.setOnViewHolderListener(new Adapter.OnViewHolderListener() {
        @Override
        public void onRequestedLastItem() {
            //TODO fetch new data from webservice
        }
    });
    return contentView;
}

其他回答

这个解决方案对我来说非常有效。

//Listener    

public abstract class InfiniteScrollListener     extendsRecyclerView.OnScrollListener {

public static String TAG = InfiniteScrollListener.class.getSimpleName();
int firstVisibleItem, visibleItemCount, totalItemCount;
private int previousTotal = 0;
private boolean loading = true;
private int visibleThreshold = 1;
private int current_page = 1;

private LinearLayoutManager mLinearLayoutManager;

public InfiniteScrollListener(LinearLayoutManager linearLayoutManager) {
    this.mLinearLayoutManager = linearLayoutManager;
}

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

    visibleItemCount = recyclerView.getChildCount();
    totalItemCount = mLinearLayoutManager.getItemCount();
    firstVisibleItem = mLinearLayoutManager.findFirstVisibleItemPosition();

    if (loading) {
        if (totalItemCount > previousTotal) {
            loading = false;
            previousTotal = totalItemCount;
        }
    }
    if (!loading && (totalItemCount - visibleItemCount - firstVisibleItem <= visibleThreshold)) {

        current_page++;

        onLoadMore(current_page);

        loading = true;
    }
}

public void resetState() {
    loading = true;
    previousTotal = 0;
    current_page = 1;
}

public abstract void onLoadMore(int current_page);
}

//Implementation into fragment 
 private InfiniteScrollListener scrollListener;

scrollListener = new InfiniteScrollListener(manager) {
        @Override
        public void onLoadMore(int current_page) {
            //Load data
        }
    };
    rv.setLayoutManager(manager);
    rv.addOnScrollListener(scrollListener);

我会尝试扩展使用的LayoutManager(例如LinearLayoutManager)和覆盖scrollVerticallyBy()方法。首先,我会先调用super,然后检查返回的整数值。如果值等于0,则到达底部或顶部边界。然后我将使用findLastVisibleItemPosition()方法来找出到达哪个边界,并在需要时加载更多数据。只是一个想法。

此外,您甚至可以从该方法中返回您的值,允许滚动并显示“loading”指示器。

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

                @Override
                public void onScrollStateChanged(RecyclerView recyclerView,int newState) 
                {
                    int totalItemCount = layoutManager.getItemCount();
                    int lastVisibleItem = layoutManager.findLastVisibleItemPosition();

                    if (totalItemCount> 1) 
                    {
                        if (lastVisibleItem >= totalItemCount - 1) 
                        {
                            // End has been reached
                            // do something 
                        }
                    }          
                }
            });  

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。

@kushal @abdulaziz

为什么不使用这个逻辑呢?

public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
    int totalItemCount, lastVisibleItemPosition;

    if (dy > 0) {
      totalItemCount = _layoutManager.getItemCount();
      lastVisibleItemPosition = _layoutManager.findLastVisibleItemPosition();

      if (!_isLastItem) {
        if ((totalItemCount - 1) == lastVisibleItemPosition) {
          LogUtil.e("end_of_list");

          _isLastItem = true;
        }
      }
    }
  }