android - Recyclerview StaggeredGridLayoutManager - 查找最后一个可见项目

Question

我正在使用带有 StaggeredGridLayoutManager 和 Endless Scroll 的 Recyclerview。当列表的最后一项对用户可见时，我想进行网络调用。所以这是我的代码:

   public RecyclerViewAdapter(Context context) {

            Log.d(Const.DEBUG, "RecyclerViewAdapter Constructor()");

            this.context = context;

            final StaggeredGridLayoutManager staggeredGridLayoutManager = (StaggeredGridLayoutManager) recyclerView.getLayoutManager();

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

                    totalItemCount = staggeredGridLayoutManager.getItemCount();
                    lastVisibleItems = staggeredGridLayoutManager.findLastVisibleItemPositions(new int[mStaggeredLayoutManager.getSpanCount()]);

                    Log.d(Const.DEBUG, "LastVisibleItems: " + Arrays.toString(lastVisibleItems));
                    Log.d(Const.DEBUG, "LastVisibleItems Count: " + lastVisibleItems.length);

                    if (staggeredGridLayoutManager.getSpanCount() == 1) {
                        lastVisibleItem = lastVisibleItems[0];
                    } else if (staggeredGridLayoutManager.getSpanCount() == 2) {
                        lastVisibleItem = Math.max(lastVisibleItems[0], lastVisibleItems[1]);
                    } else if (staggeredGridLayoutManager.getSpanCount() == 3) {
                        lastVisibleItem = Math.max(Math.max(lastVisibleItems[0], lastVisibleItems[1]), lastVisibleItems[2]);
                    }


                    if (!isRefreshing && (totalItemCount <= lastVisibleItem + visibleThreshold)) {

                        Log.d(Const.DEBUG, "isRefreshing: " + isRefreshing);
                        Log.d(Const.DEBUG, "totalItemCount: " + totalItemCount);
                        Log.d(Const.DEBUG, "lastVisibileItem: " + lastVisibleItem);
                        Log.d(Const.DEBUG, "visibileThreshold: " + visibleThreshold);

                        Log.d(Const.DEBUG, "calling LoadMore()");

                        if (mIOnLoadMoreListener != null) {
                            mIOnLoadMoreListener.onLoadMore();
                        }

                        isRefreshing = true;
                    }
                }
            });

        }

我在第一次调用时从服务器获得了 9 个值。因此，当我移动到最后一个索引 [8] 时，lastVisibleItem 将为 8，visibleThreshold 为 1，totalItemCount 为 9，因此下一次网络调用应该发生。现在实际发生的事情是，当第一次加载屏幕时，lastVisibleItem 应该是 1 或 2，但它返回 8，因此，将调用 loadMore()。

日志:

D/xx: Items Count: 9
D/xx: LastVisibleItems: [8]
03-22 15:22:52.772 5957-5957/codsiga.com.xx D/xx: LastVisibleItems Count: 1
03-22 15:22:52.772 5957-5957/codsiga.com.xx D/xx: isRefreshing: false
03-22 15:22:52.772 5957-5957/codsiga.com.xx D/xx: totalItemCount: 9
03-22 15:22:52.772 5957-5957/codsiga.com.xx D/xx: lastVisibileItem: 8
03-22 15:22:52.772 5957-5957/codsiga.com.xx D/xx: visibileThershold: 1
03-22 15:22:52.772 5957-5957/codsiga.com.xx D/xx: calling LoadMore()
03-22 15:22:52.772 5957-5957/codsiga.com.xx D/xx: onLoadMore()
03-22 15:22:52.798 5957-5957/codsiga.com.xx D/xx: getDataFromServer()

上面的代码有什么问题？需要帮助请叫我。相同的代码以前运行良好。

Answer 1

试试这个。

    private int pastVisiblesItems, visibleItemCount, totalItemCount;
        private boolean loading = true;   
        private StaggeredGridLayoutManager layoutManager;
        private RecyclerView recyclerView ;

    @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            layoutManager=new StaggeredGridLayoutManager(2,1);
            recyclerView = (RecyclerView) findViewById(R.id.recycler_view);   
            recyclerView.setLayoutManager(layoutManager);
            recycleView.addOnScrollListener(new RecyclerView.OnScrollListener() {
                    @Override
                    public void onScrolled(RecyclerView recyclerView, int dx, int dy) {

                        if (dy > 0) //for vertical scrolling
                        {

                        } else if (dy < 0) {

                        }
                        if (dx > 0)//for horizontal scrolling
                        {
                           visibleItemCount = layoutManager.getChildCount();
                            totalItemCount = layoutManager.getItemCount();
                            pastVisiblesItems = layoutManager.findFirstVisibleItemPosition();

                            if (loading) {
                                if ((visibleItemCount + pastVisiblesItems) >= totalItemCount) {
                                    loading = false;                        
                                    loadMore();  //desired function call                      
                                }
                            }
                        } 
                    }
                });
    }

API调用成功后请不要忘记设置loading=true。

希望对你有帮助