Navigation in Jetpack Compose

import androidx.navigation3.runtime.NavKey
import kotlinx.serialization.Serializable

@Serializable data object Home : NavKey
@Serializable data object ProductList : NavKey
@Serializable data class Product(val id: String) : NavKey      // arguments are just properties
@Serializable data object Cart : NavKey

@Composable
fun AppNavigation() {
    val backStack = rememberNavBackStack(Home)          // saveable back stack

    NavDisplay(
        backStack = backStack,
        onBack = { backStack.removeLastOrNull() },
        entryDecorators = listOf(
            rememberSaveableStateHolderNavEntryDecorator(),   // per-entry rememberSaveable state
            rememberViewModelStoreNavEntryDecorator(),        // per-entry ViewModels
        ),
        entryProvider = entryProvider {
            entry<Home> {
                HomeScreen(onBrowse = { backStack.add(ProductList) })
            }
            entry<ProductList> {
                ProductListScreen(onProductClick = { id -> backStack.add(Product(id)) })
            }
            entry<Product> { key ->
                ProductScreen(
                    viewModel = viewModel { ProductViewModel(productId = key.id) },
                    onAddedToCart = { backStack.add(Cart) },
                )
            }
            entry<Cart> {
                CartScreen(onDone = { backStack.removeAll { it != Home } })   // pop back to Home
            }
        },
    )
}

backStack.add(Product("42"))                          // navigate forward
backStack.removeLastOrNull()                           // back
backStack.removeAll { it is Product }                  // pop all product screens
backStack.clear(); backStack.add(Home)                 // reset (e.g. after logout)

// Avoid duplicates when tapping the same tab twice
fun NavBackStack<NavKey>.navigateTopLevel(key: NavKey) {
    if (lastOrNull() != key) { removeAll { it != Home }; if (key != Home) add(key) }
}

@Serializable object HomeRoute
@Serializable data class ProductRoute(val id: String)

@Composable
fun AppNavHost(navController: NavHostController = rememberNavController()) {
    NavHost(navController, startDestination = HomeRoute) {
        composable<HomeRoute> {
            HomeScreen(onProductClick = { id -> navController.navigate(ProductRoute(id)) })
        }
        composable<ProductRoute> { entry ->
            val route: ProductRoute = entry.toRoute()
            ProductScreen(productId = route.id, onBack = navController::popBackStack)
        }
    }
}