Compose Navigation + Paging + ViewModel + Flow

main.kt

const val LIST = "list"
const val OTHER = "other"

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            val navController = rememberNavController()
            ComposeSampleTheme {
                Scaffold(
                    bodyContent = { MainNavHost(navController) },
                    bottomBar = { BottomNav(navController) }
                )
            }
        }
    }
}

@Composable
fun BottomNav(navController: NavHostController) {
    BottomNavigation {
        val screens = listOf(LIST, OTHER)
        screens.forEach {
            BottomNavigationItem(
                icon = { Text(it) },
                selected = false,
                onClick = {
                    navController.navigate(it) {
                        launchSingleTop = true
                        popUpTo = navController.graph.startDestination
                    }
                }
            )
        }
    }
}

@Composable
fun MainNavHost(navController: NavHostController) {
    val lazyListState = rememberLazyListState()
    val listViewModel: ListViewModel = viewModel()
    val items = listViewModel.pagerFlow.collectAsLazyPagingItems() // works if done here
    NavHost(navController = navController, startDestination = LIST) {
        composable(LIST) {
            // val items = listViewModel.pagerFlow.collectAsLazyPagingItems() // does not work if done here
            LazyColumn(
                modifier = Modifier.fillMaxSize(),
                state = lazyListState
            ) {
                items(items) { Text("Item #$it") }
            }
        }
        composable(OTHER) { Text("Coucou !") }
    }
}

class ListViewModel : ViewModel() {
    private val pagingConfig = PagingConfig(pageSize = 10)
    private val pager = Pager(pagingConfig) { IntsPagingSource() }
    val pagerFlow = pager.flow.cachedIn(viewModelScope)
}

class IntsPagingSource : PagingSource<Int, Int>() {
    override suspend fun load(params: LoadParams<Int>): LoadResult<Int, Int> {
        val page = params.key ?: 0
        val pageSize = params.loadSize
        Log.d("FETCH", "PAGE #$page")
        return LoadResult.Page(
            data = List(pageSize) { (page * pageSize) + it },
            prevKey = null,
            nextKey = page + 1,
        )
    }
}