在显示带有分页库3的进度栏后加载新项

Question

我有实现性分页库3，它工作并显示数据，我需要实现的是加载更多的功能，所以当用户向下滚动时，它会获取一个页面10项，所以基本上在加载新数据之间，我希望在底部显示一个进度条，但是由于这是我第一次使用分页库3，我不知道如何做到这一点，如果有人可以的话，谢谢。

• ，我试图根据适配器类的加载状态显示和隐藏进度条，但没有显示

。

    lifecycleScope.launch {
           newsAdapter.loadStateFlow.collectLatest { loadingState ->
               if(loadingState.refresh is LoadState.Loading){
                   binding.progressBar.visibility = View.GONE
               }
               if(loadingState.refresh is LoadState.Loading) {
                   binding.progressBar.visibility = View.VISIBLE
               }
               if(loadingState.refresh is LoadState.NotLoading){
                   binding.progressBar.visibility = View.GONE
               }

           }
       }

Answer 1

用于向下滚动的LoadState是CombinedLoadStates.append，而不是.refresh，当列表被替换时(初始加载/刷新)。

实际上，如果您对LoadState感知的ConcatAdapter风格的页脚感兴趣，那么分页有一个内置的内容，请参阅：https://developer.android.com/topic/libraries/architecture/paging/v3-paged-data#load-state-adapter

Answer 2

查看https://medium.com/@yash786agg/jetpack-paging-3-0-android-bae37a56b92d，我发现我们也应该观察append状态，正如@dlam所写的那样。

adapter.addLoadStateListener { loadState ->

    if (loadState.refresh is LoadState.Loading ||
        loadState.append is LoadState.Loading)
        // Show ProgressBar
    else {
        // Hide ProgressBar

        // If we have an error, show a toast
        val errorState = when {
            loadState.append is LoadState.Error -> loadState.append as LoadState.Error
            loadState.prepend is LoadState.Error ->  loadState.prepend as LoadState.Error
            loadState.refresh is LoadState.Error -> loadState.refresh as LoadState.Error
            else -> null
        }
        errorState?.let {
            Toast.makeText(this, it.error.toString(), Toast.LENGTH_LONG).show()
        }
    }
}