How would I go about remembering my scroll position so that I can navigating back to it? `LazyListSt...

# compose-wear

[Nat Strangerweather]

How would I go about remembering my scroll position so that I can navigating back to it? LazyListState has firstVisibleItemIndex, but it seems as if ScalingLazyListState doesn't.

[yschimke]

rememberScalingLazyListState() will do it. I think it's positioned from the center, but raise a bug if you find it's not restoring position.

[yschimke]

https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:wear/compose/compose-material/src/main/java/androidx/wear/compose/material/ScalingLazyListState.kt;l=385?q=Rememberscaling

[Nat Strangerweather]

Actually, I did not express myself properly. What I need is to get the scroll position of my scalingLazyList. I can't seem to do it without the firstVisibleItemIndex. Is there an example that I could use, or could you please point me in the right direction?

[yschimke]

listState.centerItemIndex and listState.centerItemScrollOffset

[yschimke]

This sample screen uses it, the sample is designed to explain the initial layout of SLC, which I frequently struggle with if using directly.

https://github.com/google/horologist/blob/main/sample/src/main/java/com/google/android/horologist/scratch/ScratchActivity.kt

[Nat Strangerweather]

Fabulous, many thanks!

[Nat Strangerweather]

Ok, I understand why it's not working for me. It's because I am using the Horologist ScalingLazyColumn like this:

columnState: ScalingLazyColumnState = ScalingLazyColumnDefaults.belowTimeText().create()

If I use the ordinary ScalingLazyColumn, it works out of the box.
So I am stuck now.

[yschimke]

I'll send you the code you need tomorrow. Horologist does this with navigation already. Just needs to be adapted for direct saveable use.

[Nat Strangerweather]

Ok, thank you, looking forward to it!

[yschimke]

Try this

@Composable
public fun rememberColumnState(factory: ScalingLazyColumnState.Factory = ScalingLazyColumnDefaults.belowTimeText()): ScalingLazyColumnState {
    val columnState = factory.create()

    columnState.state = rememberSaveable(saver = ScalingLazyListState.Saver) {
        columnState.state
    }

    return columnState
}

[yschimke]

Usable like

val columnState = rememberColumnState(
            ScalingLazyColumnDefaults.scalingLazyColumnDefaults(
                initialCenterIndex = initialOffset.index,
                initialCenterOffset = initialOffset.offset,
                autoCentering = autoCentering,
                anchorType = anchorType
            )
        )

[Nat Strangerweather]

Works perfectly! Many thanks. 👍