Jetpack Compose LazyColumn with animated header

MainActivity.kt

package de.thomaskuenneth.animatedheaderdemo

import android.os.Bundle
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.compose.animation.AnimatedVisibility
import androidx.compose.foundation.background
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.lazy.LazyColumn
import androidx.compose.foundation.lazy.itemsIndexed
import androidx.compose.foundation.lazy.rememberLazyListState
import androidx.compose.material3.MaterialTheme
import androidx.compose.material3.Text
import androidx.compose.runtime.Composable
import androidx.compose.runtime.LaunchedEffect
import androidx.compose.runtime.derivedStateOf
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.runtime.setValue
import androidx.compose.ui.Modifier
import androidx.compose.ui.text.style.TextAlign
import androidx.compose.ui.unit.dp
import kotlinx.coroutines.delay


class MainActivity : ComponentActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            MaterialTheme {
                val list = mutableListOf<ListItem>()
                (1..10).forEach { headerIndex ->
                    (1..(3..10).random()).forEach { itemIndex ->
                        list.add(
                            ListItem(
                                header = "Header #$headerIndex",
                                text = "Item #$itemIndex"
                            )
                        )
                    }
                }
                LazyColumnDemo(list)
            }
        }
    }
}

data class ListItem(val header: String, val text: String)

@Composable
fun LazyColumnDemo(items: List<ListItem>) {
    Box(
        modifier = Modifier
            .fillMaxSize()
            .background(color = MaterialTheme.colorScheme.background)
    ) {
        val listState = rememberLazyListState()
        LazyColumn(state = listState) {
            itemsIndexed(items = items) { index, item ->
                if ((index == 0) || items[index - 1].header != item.header) {
                    Header(text = item.header)
                }
                Item(text = item.text)
            }
        }
        val currentHeader by remember {
            derivedStateOf {
                items[listState.firstVisibleItemIndex].header
            }
        }
        var lastHeader by remember { mutableStateOf(currentHeader) }
        val headerVisible by remember(
            currentHeader, lastHeader
        ) { mutableStateOf(lastHeader != currentHeader) }
        AnimatedVisibility(visible = headerVisible) {
            Header(text = currentHeader)
            LaunchedEffect(key1 = currentHeader) {
                delay(3000)
                lastHeader = currentHeader
            }
        }
    }
}

@Composable
fun Header(text: String) {
    Text(
        text = text,
        modifier = Modifier
            .fillMaxWidth()
            .padding(all = 16.dp),
        style = MaterialTheme.typography.headlineSmall,
        textAlign = TextAlign.Center
    )
}

@Composable
fun Item(text: String) {
    Text(
        text = text,
        modifier = Modifier
            .fillMaxWidth()
            .padding(all = 16.dp),
        style = MaterialTheme.typography.bodyLarge,
        textAlign = TextAlign.Center
    )
}