如何在 Android 中使用 Paging 3 库显示空视图

Question

我想在 paging3 加载一个空列表时显示空视图。

它似乎适用于以下代码。这是使用 paging 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

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 2

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 3

在我的情况下，如果它们小于 11，我必须使用 concatAdapter 来显示空视图低于正常结果。不幸的是，分页 3 库会给我很多关于 @987654321 的误报结果@ 和 loadState.append.endOfPaginationReached 状态所以我不得不通过引入一个计数器来仔细检查它。 Florian 或 Paul 的答案都可以。

     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
    }