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

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();
                }
            });
        }
    }
}

其他回答

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);
    }
}

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

@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;
        }
      }
    }
  }

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
            }

Create an abstract class and extends RecyclerView.OnScrollListener public abstract class EndlessRecyclerOnScrollListener extends RecyclerView.OnScrollListener { private int previousTotal = 0; private boolean loading = true; private int visibleThreshold; private int firstVisibleItem, visibleItemCount, totalItemCount; private RecyclerView.LayoutManager layoutManager; public EndlessRecyclerOnScrollListener(RecyclerView.LayoutManager layoutManager, int visibleThreshold) { this.layoutManager = layoutManager; this.visibleThreshold = visibleThreshold; } @Override public void onScrolled(RecyclerView recyclerView, int dx, int dy) { super.onScrolled(recyclerView, dx, dy); visibleItemCount = recyclerView.getChildCount(); totalItemCount = layoutManager.getItemCount(); firstVisibleItem = ((LinearLayoutManager)layoutManager).findFirstVisibleItemPosition(); if (loading) { if (totalItemCount > previousTotal) { loading = false; previousTotal = totalItemCount; } } if (!loading && (totalItemCount - visibleItemCount) <= (firstVisibleItem + visibleThreshold)) { onLoadMore(); loading = true; } } public abstract void onLoadMore();} in activity (or fragment) add addOnScrollListener to recyclerView LinearLayoutManager mLayoutManager = new LinearLayoutManager(this); recyclerView.setLayoutManager(mLayoutManager); recyclerView.addOnScrollListener(new EndlessRecyclerOnScrollListener(mLayoutManager, 3) { @Override public void onLoadMore() { //TODO ... } });