Recyclerview StaggeredGridLayoutManager - 查找最後一個可見項

Question

我正在使用RecyclerView和StaggeredGridLayoutManager以及無盡滾動。當列表的最後一項對用戶可見時，我想進行網絡調用。所以這裏是我的代碼：

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; 
        } 
       } 
      }); 

     } 

我在第一次調用時從服務器獲得9個值。所以，當我移動到最後一個索引[8]時，lastVisibleItem將爲8，visibleThreshold爲1，totalItemCount爲9，因此下一次網絡調用應該發生。現在實際發生的情況是，當屏幕第一次加載時，lastVisibleItem應該是1或2，但是它返回8，結果，loadMore（）被調用。

的logcat：

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() 

什麼是錯在上面的代碼？需要幫助請叫我。相同的代碼之前運作良好。

Answer 1

試試這個。

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      
           } 
          } 
         } 
        } 
       }); 
    } 

請不要忘記將負荷=真 API調用成功後。

希望它可以幫助..

Answer 2

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

       if (dy > 0) { 

        totalItemCount = staggeredGridLayoutManager.getItemCount(); 
        if (lastPositions == null) 
         lastPositions = new int[staggeredGridLayoutManager.getSpanCount()]; 
        lastPositions = staggeredGridLayoutManager.findLastCompletelyVisibleItemPositions(lastPositions); 
        lastVisibleItem = Math.max(lastPositions[0], lastPositions[1]);//findMax(lastPositions); 

        if (!loading && totalItemCount >= 20 && totalItemCount <= (lastVisibleItem + visibleThreshold)) { 
         // End has been reached 
         if (onLoadMoreListener != null) { 
          onLoadMoreListener.onLoadMore(); 
         } 
         loading = true; 
        } 
       } 
      } 
     }); 
    }