使用 Jetpack Compose Paging3，在 Launch Effect 块中的分页项目上调用 refresh() 不会更新 UI

Question

I've applied Paging3 compose with my Android Jetpack Compose project. In one of my screens, the following code is implemented to refresh the list on navigating back from another screen.

LaunchEffect(key1 = Unit) {
      items.refresh()
}

The initial recomposition on navigation back indeed triggers the lambda block in Launch Effect but doesn't reschedule the recomposition again to update the LazyColumn.

LazyColumn(
     modifier = Modifier.fillMaxSize()
) {
     item { Spacer(modifier = Modifier.height(14.dp)) }
     items(items) { item ->
          Item(blog = item!!)
     }
}

Please suggest me a solution to fix this. Right now, I've removed cacheIn() in view model just to force pager to refetch new objects but that'll bring back to page 1, apparently not how it's supposed to be. Also, if we wrap the lazy column with Swipe Refresh and manually refresh, bothe the data and UI got updated. Any solution for this?

Answer 1

I had the same problem as you, and after experimenting I found that there was some differences reg coroutine calls when using LaunchEffect vs fx SwipeToRefresh calls to items.refresh().

So I tried this and it worked for me:

LaunchEffect(key1 = Unit) {
    launch(Dispatchers.Main) {
        items.refresh()
    }
}

Exactly why this works and if there are any unwanted side-effects I don't know.

Bonus info from my small experiment:

• Dispatchers.Default also worked.
• Dispatchers.IO worked sometimes .
• Dispatchers.Unconfined had no effect.
• launch{...} completely invalidated my list (items disappeared while loading)
• launch(Job()){...} completely invalidated my list (items disappeared while loading)
• launch(newSingleThreadContext("MyOwnThread")){...} worked sometimes .