Jetpack compose remember function not working - kotlin

Question

I'm trying to create a scrollable background in Jetpack Compose.
The problem is that the variable "currentPadding" isn't updating it's state after the value "padding" is modified after recomposition. In the first composition (loading state) the "padding" value is set to 112.dp and after load the value changes to 160.dp.
It's strange because I have used the remember function this way multiple times in other places in the app and it's the first time that this happens.
Could you help me out?
Thanks a lot.
#Composable
fun ScrollableBackground(
scrollState: ScrollState,
composable: ComposableFun,
modifier: Modifier = Modifier,
isBannerListEmpty: Boolean,
) {
val padding = if (isBannerListEmpty) {
112.dp
} else {
160.dp
}
val minPadding: Dp = 29.dp
val dp0 = dimensionResource(id = R.dimen.no_dp)
var currentPadding: Dp by remember { mutableStateOf(padding) }
val state: Dp by animateDpAsState(targetValue = currentPadding)
val nestedScrollConnection: NestedScrollConnection = remember {
object : NestedScrollConnection {
override fun onPreScroll(available: Offset, source: NestedScrollSource): Offset {
val percent = scrollState.value.toFloat() / scrollState.maxValue.toFloat() * 100f
val delta = available.y.dp
val newSize = currentPadding + delta / 3
currentPadding = when {
percent > 20f -> minPadding
newSize < minPadding -> minPadding
newSize > padding -> padding
else -> newSize
}
return Offset.Zero
}
}
}
Box(
modifier = modifier
.fillMaxSize()
.nestedScroll(nestedScrollConnection)
) {
Surface(
color = White,
modifier = Modifier
.padding(top = state)
.fillMaxSize()
.clip(
CircleShape.copy(
topStart = Shapes.medium.topStart,
topEnd = Shapes.medium.topEnd,
bottomEnd = CornerSize(dp0),
bottomStart = CornerSize(dp0)
)
)
) {}
composable.invoke()
}
}
I tried sending other kind of parameters from the view model to the composable (instead of a boolean, in this case "isBannerListEmpty"), like the current desired padding value, and nothing seems to work.

Answer 1

You have put nestedScrollConnection in remember. It also remembers the padding variable when first encountered. So when the actual value of padding is changed, this change is not propagated in remember of nestedScrollConnection.
Put padding inside onPreScroll.
override fun onPreScroll(available: Offset, source: NestedScrollSource): Offset {
val padding = if (...) { //Don't use isBannerListEmpty here as neither this will update on recomposition
112.dp
} else {
160.dp
}
...