Android页面库如何调用LoadAfter只有当我到达可见/加载数据的末尾时?

我使用PageKeyedDataSource来实现无限滚动列表。它起作用了。它看起来像这样(简化版):

class ProfilePostDataSource: PageKeyedDataSource<Pair<Long, Long>, ProfilePost> {
  fun loadInitial(... ...) {
    val list = retrofitClient.getSomeData();
    callback.onResult(list, null, next);
  }

  fun loadBefore(...) {} 

  fun loadAfter(...) { 
    val pageNumber = params.key;
    val next = pageNumber + 1;   
    Log.e(TAG, "onLoadAfter -> "+pageNumber);   // <---------- tells me in the log which page is loading
    val list = retrofitClient.getSomeData(pageNumber);
    callback.onResult(list, next);
  }
}

        //1
        val config: PagedList.Config = PagedList.Config.Builder()
                .setPageSize(15)          // Don't google. Hit ctrl+b and read doc. Be happy
                .setPrefetchDistance(1)  // Don't google. Hit ctrl+b and read doc. Be happy
                .setMaxSize(32)           // Don't google. Hit ctrl+b and read doc. Be happy
                .setEnablePlaceholders(false) // true -> show a dummy placeholder for unloaded items. false -> dont show
                .build();

loadAfter() 太快了。所以在我的日志里,我看到了:

onLoadAfter -> 2   
onLoadAfter -> 3
onLoadAfter -> 4
onLoadAfter -> 5   // 5 / 6 loadAfter are called

所以当我完成我的清单,下一个 loadAfter 被称为。

onLoadAfter ->6 // only one loadAfter is called. Subsequently, when I scroll to the end, the next loadAfter is called