android - RecyclerView Infinite Scroll 监听器被调用两次

Question

我有一个 RecyclerView，我试图在其中实现无限滚动功能。问题是，OnScrolled 方法中 if 语句中的代码被执行了两次。这是我当前的代码:

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);
}

这段代码是作为对一个单独的 SO 问题的回答而发布的，其他示例的功能似乎相似，但我仍然在到达 底部时执行了两次 loadMore() 方法>RecyclerView，我不确定为什么。

Answer 1

它被调用是因为当您加载更多项目时，onScrolled 会再次被调用。

This callback will also be called if visible item range changes after a layout calculation. In that case, dx and dy will be 0.

所以你可以检查if (!loading && dy>0)还有