ComposeNestedScrollSampleCompleteCode.kt

Surface(
    modifier = Modifier.fillMaxSize(),
    color = MaterialTheme.colorScheme.background
) {
    val appBarMaxHeightPx = with(LocalDensity.current) { AppBarHeight.roundToPx() }
    val connection = remember(appBarMaxHeightPx) {
        CollapsingAppBarNestedScrollConnection(appBarMaxHeightPx)
    }
    val density = LocalDensity.current
    val spaceHeight by remember(density) {
        derivedStateOf {
            with(density) {
                (appBarMaxHeightPx + connection.appBarOffset).toDp()
            }
        }
    }

    Box(Modifier.nestedScroll(connection)) {
        Column {
            Spacer(
                Modifier
                    .padding(4.dp)
                    .height(spaceHeight)
            )
            LazyColumn {
                items(Contents) {
                    ListItem(item = it)
                }
            }
        }

        TopAppBar(
            modifier = Modifier.offset { IntOffset(0, connection.appBarOffset) },
            title = { Text(text = "Jetpack Compose") },
            colors = TopAppBarDefaults.topAppBarColors(
                containerColor = Purple40,
                titleContentColor = Color.White
            )
        )
    }
}