如何在 Android 中使用 Paging 3 库显示空视图

Question

我想在 paging3 加载空列表时显示空视图。

它似乎适用于以下代码。这是处理分页 3 库的正确方法吗？:

        adapter?.addLoadStateListener { loadState ->
            adapter?.apply {
                if (itemCount <= 0 && !loadState.source.refresh.endOfPaginationReached) {
                    Timber.d("==> to show empty view")
                    tvEmptyView.isGone = false
                } else {
                    Timber.d("==> to hide empty view")
                    tvEmptyView.isGone = true
                }
            }
        }

Answer 1

您可以直接插入适配器loadStateFlow，例如

    lifecycleScope.launchWhenCreated {
        @OptIn(ExperimentalCoroutinesApi::class)
        adapter.loadStateFlow.collectLatest { loadStates ->
            val refresher = loadStates.refresh
            val displayEmptyMessage =  (refresher is LoadState.NotLoading && refresher.endOfPaginationReached && adapter.itemCount == 0)
            layoutBinding.emptyStateMessage.isVisible = displayEmptyMessage
            layoutBinding.emptyStateImage.isVisible = displayEmptyMessage
            layoutBinding.swipeToRefresh.isRefreshing = refresher is LoadState.Loading
        }
    }

Answer 2

这对我有用：

if (loadState.source.refresh is LoadState.NotLoading &&
    loadState.append.endOfPaginationReached &&
    adapter.itemCount < 1
) {
   recyclerView.isVisible = false
   textViewEmpty.isVisible = true
} else {
    textViewEmpty.isVisible = false
}

Answer 3

在我的例子中，如果它们小于 11，我不得不使用 concatAdapter 来显示低于正常结果的空视图。不幸的是，分页 3 库会给我很多误报关于 LoadState.NotLoading 和 loadState.append.endOfPaginationReached 状态的结果，所以我不得不通过引入计数器来仔细检查它。 Florian 或 Paul 的回答都可以。

     offersAdapter.addLoadStateListener { updateUiOnNewLoadSate(it) }
    
     private fun updateUiOnNewLoadSate(loadState: CombinedLoadStates) {
    
            Timber.i("STATE $loadState")
          
            // Show empty view if results are less or equal 10
            val displayEmptySearch =
                loadState.source.refresh is LoadState.NotLoading && loadState.append.endOfPaginationReached && offersAdapter.itemCount <= 10 && loadStatesCounter > 1
            if (displayEmptySearch) {
    //here I display the empty view as a part of the
   //infinite scrolling recyclerview by using concatAdapter
                concatAdapter.addAdapter(emptyViewAdapter)
            } else {
                concatAdapter.removeAdapter(emptyViewAdapter)
            }
            loadStatesCounter++ //only apply above block when loadStatesCounter > 1
    }

如何在 Android 中使用 Paging 3 库显示空视图

How to show empty view with Paging 3 library in Android

android

android-layout

android-paging-3