How to prevent autoscroll on LazyColumn update if ...

# compose

[K Merle]

How to prevent autoscroll on LazyColumn update if item index 0 is not visible?

[K Merle]

Every new item that arrives as index 0 makes scroll move for that item height.

[FunkyMuse]

Can you share the code?

[K Merle]

I am unable to share code as it's company project. Should adding an new item to an index 0 not move scroll for that same height amount?

[Dmitrii Smirnov]

and we are unable to answer questions like "I can't show you what I do but what am I doing wrong?"

[K Merle]

I am asking a question, in a sense of, is something true or false. Sorry for not being able to share code.

[K Merle]

Should adding an new item to an index 0 not move scroll for that same height amount?

[Dmitrii Smirnov]

nobody ask you to violate NDA, you can easily share some part of it, replacing sensitive data with "something" - just like in previous question

[Dmitrii Smirnov]

generally it works like "i want some behavior from this code, and it works in another way plz help"

[K Merle]

Lol, okay mate. Here it is.

val lazyListState = rememberLazyListState()
    LazyColumn(
        state = lazyListState,
        reverseLayout = true,
        modifier = modifier
    ) {
        items(messages) { item ->
            MessageItem(item)
        }
}

[Abhinav Suthar]

If you don't provide key then index is used as key. Now assume this
nth item is focused and another item at index 0 is added. So now new nth item (previously (n-1)th item) is now focused.

Try providing unique key per item(message) to items extention function

[K Merle]

Thanks. This solved issue. I was using sealed class for my data and sealed class did not contain any properties. Passing an id to a sealed class and as a key inside items(..,key={id}) solved an issue.

[K Merle]

My first issue was solved with keys, but I've found different issue now. Scrolling to the end of list and Navigating from Screen A that contains this LazyColumn, to Screen B, and returning does not position scroll correctly. Using something like this solves the problem, but looks like hack. Am I missing something? Worth mentioning is that I am showing messages and pictures from the device storage with Coil.

val itemOffset = rememberSaveable { mutableStateOf(0)}
    LaunchedEffect(itemOffset) {
        lazyListState.animateScrollToItem(lazyListState.firstVisibleItemIndex, itemOffset.value)
    }

    SideEffect {
        itemOffset.value = lazyListState.firstVisibleItemScrollOffset
    }

[John Nichol]

For your second issue you need to hoist the LazyListState up so that it is remembered by whatever is composing Screen A, Otherwise a new LazyListState is going to be created and this contains the scroll position.