Hi, I would like to scroll to top when I update my...

# compose

[Raed Ghazal]

Hi, I would like to scroll to top when I update my LizyColumn data (on refresh), here is how I did it

LaunchedEffect(state.receipts) {
    if (state.receipts.isNotEmpty()) {
        listState.scrollToItem(0)
    }
}

but it doesn't always work, its always called, but it doesn't scroll, and my guess here is that the LazyColumn hasn't rendered/updated its content yet at this point so it scrolls in the old list, then updates the list with new data,

if I put a delay(500) before calling scrollToItem it works, but I don't wanna put some random value, that might not work for slower devices, any advise here?

[Raed Ghazal]

example of what happens:

old list:
receipt x <--- first visible item
receipt y
receipt z

new list after refresh:
receipt a
receipt x <--- still first visible item, I have to scroll up to see `a`
receipt y
receipt z

[Louis]

I think it would be simpler if you put an empty item at the beginning, so that the anchoring is done on this one and you'll see your new items appear at the beginning of your list

[Louis]

item {}

[Raed Ghazal]

hmmm

[Raed Ghazal]

this kinda makes sense, but it feels hacky xD

[Louis]

The only difference is that it only works if you're already at the top of the list (and not if you've already scrolled).

[Raed Ghazal]

I think it will work with my above scroll to item 0 even if we're at the middle

cuz if my call happens before rendering the new list, the empty item will become first and then stay first, and if my call happens after rendering the list, then it will scroll correctly, let me give it a try

[Raed Ghazal]

it actually worked 😄 I'll keep it for now till I find a better solution thats intuitively understandable, I'm sure I'll be confused in the future of why I have this empty item

[Dmitry Strekha]

try requestScrollToItem
https://developer.android.com/reference/kotlin/androidx/compose/foundation/lazy/LazyListState#requestScrollToItem(kotlin.Int,kotlin.Int)

here's example of usage - https://x.com/and_kulikov/status/1775574132207358264

[Raed Ghazal]

oh thanks for sharing @Dmitry Strekha!

I did try requestScrollToItem but it had the same issue, I guess what I did wrong was using LaunchEffect rather than SideEffect which runs AFTER the composition is done, while LaunchEffect actually ran at the beginning of the composition so it was getting invoked before the list gets the state change

[efemoney]

LaunchedEffect does not run at the beginning of (or before) composition. Its also run after composition.