Question

我有一个RecyclerView，我希望它从顶部拉出时是SwipeRefreshLayout，所以我可以获得最新的20项并在RecyclerView上显示它。同时，当到达底部的第20项时，然后获取另一个来自数据库的第20项。

因此，我得到了下面的最后一项，所以我可以获取下一个第20项。

//for endless scroll
    recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {

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

            visibleItemCount = recyclerView.getChildCount();
            totalItemCount = mLayoutManager.getItemCount();
            firstVisibleItem = mLayoutManager.findFirstVisibleItemPosition();

            if (loading) {
                if (totalItemCount > previousTotal) {
                    loading = false;
                    previousTotal = totalItemCount;
                }
            }
            if (!loading && (totalItemCount - visibleItemCount)
                    <= (firstVisibleItem + visibleThreshold)) {
                // End has been reached

                Log.i("Yaeye!", "end called");
                fetchPost(feedItems.get(feedItems.size()-1).getId());
                //This function is fetch the next 20th item from database




                // Do something

                loading = true;
            }
        }
    });

}

当它到达Recycleview的底部时，这是好的，但问题是当现在是顶部（RecyclerView中的第一项）时，我拉下来，假设它获取新项目，但它崩溃。这是错误：

java.lang.ArrayIndexOutOfBoundsException：length = 27;指数= -1

以下是我的代码：，SwipeRefreshLayout获取数据库中的最新第20项

// show loader and fetch messages
    swipeRefreshLayout.post(
            new Runnable() {
                @Override
                public void run() {
                    clear();
                    fetchIntialPost(); // this one,fetch the latest item
                }
            }
    );

所以我知道它引起的，当在第1项时，它也考虑到RecyclerView的结束，所以它调用fetchPost(feedItems.get(feedItems.size()-1).getId());这个函数而不是这个函数fetchIntialPost();

所以现在我的问题是，当在顶部（第1项）时，在向下拉fetchIntialPost();时调用SwipeRefreshLayout？和最后一项，只需致电fetchPost(feedItems.get(feedItems.size()-1).getId());。

由于

Answer 1

我在执行此行代码feedItems.size()-1之前检查fetchPost(feedItems.get(feedItems.size()-1).getId());的值来解决此问题

这是我的工作代码：

//top and bottom also consider end of the list
recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {

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

            visibleItemCount = recyclerView.getChildCount();
            totalItemCount = mLayoutManager.getItemCount();
            firstVisibleItem = mLayoutManager.findFirstVisibleItemPosition();
            lastVisibleItem = mLayoutManager.findLastVisibleItemPosition();

            if (loading) {
                if (totalItemCount > previousTotal) {
                    loading = false;
                    previousTotal = totalItemCount;
                }
            }
            if (!loading && (totalItemCount - visibleItemCount)
                    <= (firstVisibleItem + visibleThreshold)) {
                // End has been reached
                //top and bottom also consider end of the list
                Log.i("Yaeye!", "end called");
                if(feedItems.size() - 1 > 0) {
                    //when pull down SwipeRefreshLayout,feedItems.size = -1
                    //so if greater than 0,means is bottom of the list
                    // Do something
                    fetchPost(feedItems.get(feedItems.size() - 1).getId());

                    loading = true;
                }else{
                  //here is the top of the list
                }
            }

        }

    });

Answer 2

你能试试吗？

lastVisibleItem = mLayoutManager.findLastVisibleItemPosition();

if (!loading && lastVisibleItem == (totalItemCount - 1)) {
  // End has been reached
}

顶部和底部的RecycleView的SwipeRefreshLayout？

2 个答案: