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

@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;
        }
      }
    }
  }

其他回答

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) {}
}

@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;
                    }
                }
            }

        }


    });

这是另一种方法。它将与任何布局管理器工作。

使Adapter类抽象 然后在适配器类中创建一个抽象方法。load ()) 在onBindViewHolder中检查位置,如果最后调用load() 在活动或片段中创建适配器对象时重写load()函数。 在重载加载函数实现你的loadmore调用

为了详细了解,我写了一篇博客文章和示例项目 http://sab99r.com/blog/recyclerview-endless-load-more/

MyAdapter.java

public abstract class MyAdapter extends RecyclerView.Adapter<ViewHolder>{

        @Override
        public void onBindViewHolder(ViewHolder holder, int position) {
            //check for last item
            if ((position >= getItemCount() - 1))
                load();
        }

        public abstract void load();
}

MyActivity.java

public class MainActivity extends AppCompatActivity {
    List<Items> items;
    MyAdapter adapter;

   @Override
    protected void onCreate(Bundle savedInstanceState) {
    ...
    adapter=new MyAdapter(items){
            @Override
            public void load() {
                //implement your load more here
                Item lastItem=items.get(items.size()-1);
                loadMore();
            }
        };
   }
}

我让你接近我。对我来说没问题。

我希望这对你有所帮助。

/**
 * Created by Daniel Pardo Ligorred on 03/03/2016.
 */
public abstract class BaseScrollListener extends RecyclerView.OnScrollListener {

    protected RecyclerView.LayoutManager layoutManager;

    public BaseScrollListener(RecyclerView.LayoutManager layoutManager) {

        this.layoutManager = layoutManager;

        this.init();
    }

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

        super.onScrolled(recyclerView, dx, dy);

        this.onScroll(recyclerView, this.getFirstVisibleItem(), this.layoutManager.getChildCount(), this.layoutManager.getItemCount(), dx, dy);
    }

    private int getFirstVisibleItem(){

        if(this.layoutManager instanceof LinearLayoutManager){

            return ((LinearLayoutManager) this.layoutManager).findFirstVisibleItemPosition();
        } else if (this.layoutManager instanceof StaggeredGridLayoutManager){

            int[] spanPositions = null; //Should be null -> StaggeredGridLayoutManager.findFirstVisibleItemPositions makes the work.

            try{

                return ((StaggeredGridLayoutManager) this.layoutManager).findFirstVisibleItemPositions(spanPositions)[0];
            }catch (Exception ex){

                // Do stuff...
            }
        }

        return 0;
    }

    public abstract void init();

    protected abstract void onScroll(RecyclerView recyclerView, int firstVisibleItem, int visibleItemCount, int totalItemCount, int dx, int dy);

}

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
                }
            }
        })