提交列表后未获取PagedListAdapter的itemCount

Question

我已基于PagedListAdapter实现了 分页功能 ，并且已经检查我可以正常工作。我尝试实现以 如果ListAdapter项为空，然后显示EmptyHolder 为特色。我在调用commitCallback之后基于submitList尝试了以下代码。

问题

  

即使响应包含项目，为什么PagedListAdapter的项目计数也显示为0？如何解决这个问题？

FooDataSource

private suspend fun loadItems(beforeId: String) = withContext(Dispatchers.IO) {
    getFooUseCase(beforeId)
}

override fun loadInitial(
    params: LoadInitialParams<String>,
    callback: LoadInitialCallback<String, Foo>
) {
    launch {
        loadItems(null)
            .run {
                Timber.d("loadInitial : ${list.size}") // onResponse : 20
                callback.onResult(list, null, beforeId)
            }
    }
}

FooListFragment

observe(fooList) { items ->
    // items.size or loadedCount always 0
    fooAdapter.submitList(items) {
        //fooAdapter.itemCount, fooAdapter.currentList.size or loadedSize
        //always 0...
        if(fooAdapter.itemCount == 0) {
            //show EmptyHolder
        }
    }
}

Answer 1

PagedList.BoundaryCallback具有onZeroItemsLoaded方法来处理空初始负载

val livedPageList = LivePagedListBuilder(sourceFactory, config)
        .setBoundaryCallback(object: PagedList.BoundaryCallback<YourItem>() {
            override fun onZeroItemsLoaded() {
                super.onZeroItemsLoaded()
                // Handle empty initial load here
            }

            override fun onItemAtEndLoaded(itemAtEnd: YourItem) {
                super.onItemAtEndLoaded(itemAtEnd)
                // Here you can listen to last item on list
            }

            override fun onItemAtFrontLoaded(itemAtFront: YourItem) {
                super.onItemAtFrontLoaded(itemAtFront)
                // Here you can listen to first item on list
            }
        })
        .build()

您可以查看完整答案here