为什么我加载不止一次时，实现加载更多的数据在回收视图的底部

Question

我实现了以下代码。它可以工作，但我多次检索它，它在我的数据中产生了许多重复。我如何使它只运行一次检索更多数据?

final LinearLayoutManager layoutManager = (LinearLayoutManager) getLayoutManager();
recyclerView.setOnScrollListener(new RecyclerView.OnScrollListener() {
	boolean loading = true;
	@Override
	public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
	    int pastVisibleItems, visibleItemCount, totalItemCount;
	    visibleItemCount = layoutManager.getChildCount();
	    totalItemCount = layoutManager.getItemCount();
	    pastVisibleItems = layoutManager.findFirstVisibleItemPosition();
	    if (loading) {
		if ((visibleItemCount + pastVisibleItems) >= totalItemCount) {
		    loading = false;
		    //retrieve more data from internet
		    loading = true;
		}
	    }
	}
});

Answer 1

结果证明下面的算法更好

private int previousTotal = 0;
private boolean loading = true;
private int visibleThreshold = 5;
int firstVisibleItem, visibleItemCount, totalItemCount;
mRecyclerView.setOnScrollListener(new RecyclerView.OnScrollListener() {
    @Override
    public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
        super.onScrolled(recyclerView, dx, dy);
        visibleItemCount = mRecyclerView.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("...", "end called");
            // Do something
            loading = true;
        }
    }
});

源