RecyclerView Infinite Scroll监听器被调用两次

Question

我有一个RecyclerView尝试实现无限滚动功能.问题是,OnScrolled方法中if语句内的代码正在执行两次.继承我目前的代码:

public abstract class InfiniteScroll extends RecyclerView.OnScrollListener {

private LinearLayoutManager mLayoutManager;
private int previousTotal = 0;
private boolean loading = true;
private int visibleThreshold = 5;
int firstVisibleItem, visibleItemCount, totalItemCount;

private int current_page = 1;

public InfiniteScroll(LinearLayoutManager layoutManager) {
    mLayoutManager = layoutManager;
}

@Override
public void onScrolled(RecyclerView recyclerView, int dx, int 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

        // Do something
        current_page++;
        Log.d("moreitems", "why is this being called twice?");
        loadMore(current_page);

        loading = true;
    }
}

public abstract void loadMore(int current_page);
}

这个代码是作为一个单独的SO问题的答案发布的,其他示例似乎功能类似,但我仍然得到该loadMore()方法执行两次到达底部时RecyclerView,我不知道为什么.

Answer 1

它被调用,因为当你加载更多项时,再次调用onScrolled.

如果在布局计算后可见项目范围发生更改,也将调用此回调.在这种情况下,dx和dy将为0.

所以你可以检查 if (!loading && dy>0) 以及

Answer 2

Try this:

 public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
                super.onScrolled(recyclerView, dx, dy);
                final LinearLayoutManager linearLayoutManager = (LinearLayoutManager) recyclerView.getLayoutManager();
                totalItemCount = linearLayoutManager.getItemCount();
                lastVisibleItem = linearLayoutManager.findLastVisibleItemPosition();
                if (!loading && totalItemCount <= (lastVisibleItem + visibleThreshold)) {
                    loading = true;
                    // End has been reached
                    // Do something
                       current_page++;
                       Log.d("moreitems", "why is this being called twice?");
                       loadMore(current_page);

                }
            }