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

这里我的解决方案使用AsyncListUtil,在网络上说: 注意,这个类使用一个线程来加载数据,所以它适合从二级存储(如磁盘)加载数据,但不适合从网络加载数据。 但是我使用odata来读取数据并工作良好。 我在示例中遗漏了数据实体和网络方法。 我只包括示例适配器。

public class AsyncPlatoAdapter extends RecyclerView.Adapter {

    private final AsyncPlatoListUtil mAsyncListUtil;
    private final MainActivity mActivity;
    private final RecyclerView mRecyclerView;
    private final String mFilter;
    private final String mOrderby;
    private final String mExpand;

    public AsyncPlatoAdapter(String filter, String orderby, String expand, RecyclerView recyclerView, MainActivity activity) {
        mFilter = filter;
        mOrderby = orderby;
        mExpand = expand;
        mRecyclerView = recyclerView;
        mActivity = activity;
        mAsyncListUtil = new AsyncPlatoListUtil();

    }

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View itemView = LayoutInflater.from(parent.getContext()).
                inflate(R.layout.plato_cardview, parent, false);

        // Create a ViewHolder to find and hold these view references, and
        // register OnClick with the view holder:
        return new PlatoViewHolderAsync(itemView, this);
    }

    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
        final Plato item = mAsyncListUtil.getItem(position);
        PlatoViewHolderAsync vh = (PlatoViewHolderAsync) holder;
        if (item != null) {
            Integer imagen_id = item.Imagen_Id.get();
            vh.getBinding().setVariable(BR.plato, item);
            vh.getBinding().executePendingBindings();
            vh.getImage().setVisibility(View.VISIBLE);
            vh.getProgress().setVisibility(View.GONE);
            String cacheName = null;
            String urlString = null;
            if (imagen_id != null) {
                cacheName = String.format("imagenes/imagen/%d", imagen_id);
                urlString = String.format("%s/menusapi/%s", MainActivity.ROOTPATH, cacheName);
            }
            ImageHelper.downloadBitmap(mActivity, vh.getImage(), vh.getProgress(), urlString, cacheName, position);
        } else {
            vh.getBinding().setVariable(BR.plato, item);
            vh.getBinding().executePendingBindings();
            //show progress while loading.
            vh.getImage().setVisibility(View.GONE);
            vh.getProgress().setVisibility(View.VISIBLE);
        }
    }

    @Override
    public int getItemCount() {
        return mAsyncListUtil.getItemCount();
    }

    public class AsyncPlatoListUtil extends AsyncListUtil<Plato> {
        /**
         * Creates an AsyncListUtil.
         */
        public AsyncPlatoListUtil() {
            super(Plato.class, //my data class
                    10, //page size
                    new DataCallback<Plato>() {
                        @Override
                        public int refreshData() {
                            //get count calling ../$count ... odata endpoint
                            return countPlatos(mFilter, mOrderby, mExpand, mActivity);
                        }

                        @Override
                        public void fillData(Plato[] data, int startPosition, int itemCount) {
                            //get items from odata endpoint using $skip and $top
                            Platos p = loadPlatos(mFilter, mOrderby, mExpand, startPosition, itemCount, mActivity);
                            for (int i = 0; i < Math.min(itemCount, p.value.size()); i++) {
                                data[i] = p.value.get(i);
                            }

                        }
                    }, new ViewCallback() {
                        @Override
                        public void getItemRangeInto(int[] outRange) {
                            //i use LinearLayoutManager in the RecyclerView
                            LinearLayoutManager layoutManager = (LinearLayoutManager) mRecyclerView.getLayoutManager();
                            outRange[0] = layoutManager.findFirstVisibleItemPosition();
                            outRange[1] = layoutManager.findLastVisibleItemPosition();
                        }

                        @Override
                        public void onDataRefresh() {
                            mRecyclerView.getAdapter().notifyDataSetChanged();
                        }

                        @Override
                        public void onItemLoaded(int position) {
                            mRecyclerView.getAdapter().notifyItemChanged(position);
                        }
                    });
            mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
                @Override
                public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
                    onRangeChanged();
                }
            });
        }
    }
}

对于那些只想在最后一项完全显示时得到通知的人,可以使用view . canscrollvertical()。

这是我的实现:

public abstract class OnVerticalScrollListener
        extends RecyclerView.OnScrollListener {

    @Override
    public final void onScrolled(RecyclerView recyclerView, int dx, int dy) {
        if (!recyclerView.canScrollVertically(-1)) {
            onScrolledToTop();
        } else if (!recyclerView.canScrollVertically(1)) {
            onScrolledToBottom();
        } else if (dy < 0) {
            onScrolledUp();
        } else if (dy > 0) {
            onScrolledDown();
        }
    }

    public void onScrolledUp() {}

    public void onScrolledDown() {}

    public void onScrolledToTop() {}

    public void onScrolledToBottom() {}
}

注意:如果你想支持API < 14,你可以使用recyclerView.getLayoutManager(). canscrollvertical()。

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);

@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;
                    }
                }
            }

        }


    });

检查的每一件事都有详细的解释: 使用RecyclerView从A到Z分页

    mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
    @Override
    public void onScrollStateChanged(RecyclerView recyclerView,
                                     int newState) {
        super.onScrollStateChanged(recyclerView, newState);
    }

    @Override
    public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
        super.onScrolled(recyclerView, dx, dy);
        int visibleItemCount = mLayoutManager.getChildCount();
        int totalItemCount = mLayoutManager.getItemCount();
        int firstVisibleItemPosition = mLayoutManager.findFirstVisibleItemPosition();

        if (!mIsLoading && !mIsLastPage) {
            if ((visibleItemCount + firstVisibleItemPosition) >= totalItemCount
                    && firstVisibleItemPosition >= 0) {
                loadMoreItems();
            }
        }
    }
})

loadMoreItems ():

private void loadMoreItems() {
    mAdapter.removeLoading();
    //load data here from the server

    // in case of success
    mAdapter.addData(data);
    // if there might be more data
    mAdapter.addLoading();
}

在MyAdapter中:

private boolean mIsLoadingFooterAdded = false;

public void addLoading() {
    if (!mIsLoadingFooterAdded) {
        mIsLoadingFooterAdded = true;
        mLineItemList.add(new LineItem());
        notifyItemInserted(mLineItemList.size() - 1);
    }
}

public void removeLoading() {
    if (mIsLoadingFooterAdded) {
        mIsLoadingFooterAdded = false;
        int position = mLineItemList.size() - 1;
        LineItem item = mLineItemList.get(position);

        if (item != null) {
            mLineItemList.remove(position);
            notifyItemRemoved(position);
        }
    }
}

public void addData(List<YourDataClass> data) {

    for (int i = 0; i < data.size(); i++) {
        YourDataClass yourDataObject = data.get(i);
        mLineItemList.add(new LineItem(yourDataObject));
        notifyItemInserted(mLineItemList.size() - 1);
    }
}