Jetpack Navigation Compose 2026: การนำทางแบบ Type-Safe และคำถามสัมภาษณ์งาน

plugins {
    id("org.jetbrains.kotlin.plugin.serialization") version "2.1.0"
}

dependencies {
    implementation("androidx.navigation:navigation-compose:2.10.0")
    implementation("org.jetbrains.kotlinx:kotlinx-serialization-json:1.7.3")
}

import kotlinx.serialization.Serializable

@Serializable
object Home

@Serializable
object ProductList

@Serializable
data class ProductDetail(val productId: String)

@Serializable
data class Checkout(val cartId: String, val promoCode: String? = null)

@Composable
fun AppNavigation(
    navController: NavHostController = rememberNavController()
) {
    NavHost(
        navController = navController,
        startDestination = Home
    ) {
        composable<Home> {
            HomeScreen(
                onNavigateToProducts = { navController.navigate(ProductList) }
            )
        }

        composable<ProductList> {
            ProductListScreen(
                onProductClick = { productId ->
                    navController.navigate(ProductDetail(productId))
                }
            )
        }

        composable<ProductDetail> { backStackEntry ->
            // ดึง route ที่มีชนิดจาก back stack entry
            val route: ProductDetail = backStackEntry.toRoute()
            ProductDetailScreen(
                productId = route.productId,
                onCheckout = { cartId ->
                    navController.navigate(Checkout(cartId))
                }
            )
        }

        composable<Checkout> { backStackEntry ->
            val route: Checkout = backStackEntry.toRoute()
            CheckoutScreen(
                cartId = route.cartId,
                promoCode = route.promoCode
            )
        }
    }
}

@Serializable
object AuthGraph  // ตัวระบุ graph

@Serializable
object Login

@Serializable
object Register

@Serializable
data class PasswordReset(val email: String)

fun NavGraphBuilder.authNavGraph(navController: NavHostController) {
    navigation<AuthGraph>(startDestination = Login) {
        composable<Login> {
            LoginScreen(
                onRegisterClick = { navController.navigate(Register) },
                onForgotPassword = { email ->
                    navController.navigate(PasswordReset(email))
                },
                onLoginSuccess = {
                    navController.navigate(Home) {
                        popUpTo<AuthGraph> { inclusive = true }
                    }
                }
            )
        }

        composable<Register> {
            RegisterScreen(
                onRegistrationComplete = {
                    navController.navigate(Home) {
                        popUpTo<AuthGraph> { inclusive = true }
                    }
                }
            )
        }

        composable<PasswordReset> { backStackEntry ->
            val route: PasswordReset = backStackEntry.toRoute()
            PasswordResetScreen(email = route.email)
        }
    }
}

@JvmInline
@Serializable
value class ProductId(val value: String)

@JvmInline
@Serializable
value class UserId(val value: String)

@Serializable
data class ProductDetail(val productId: ProductId)

@Serializable
data class UserProfile(val userId: UserId)

composable<ProductDetail>(
    deepLinks = listOf(
        navDeepLink {
            uriPattern = "https://example.com/products/{productId}"
        }
    )
) { backStackEntry ->
    val route: ProductDetail = backStackEntry.toRoute()
    ProductDetailScreen(productId = route.productId)
}

<!-- AndroidManifest.xml -->
<activity android:name=".MainActivity">
    <intent-filter>
        <action android:name="android.intent.action.VIEW" />
        <category android:name="android.intent.category.DEFAULT" />
        <category android:name="android.intent.category.BROWSABLE" />
        <data
            android:scheme="https"
            android:host="example.com"
            android:pathPrefix="/products" />
    </intent-filter>
</activity>

NavHost(
    navController = navController,
    startDestination = Home,
    enterTransition = { slideIntoContainer(AnimatedContentTransitionScope.SlideDirection.Start) },
    exitTransition = { slideOutOfContainer(AnimatedContentTransitionScope.SlideDirection.Start) },
    popEnterTransition = { slideIntoContainer(AnimatedContentTransitionScope.SlideDirection.End) },
    popExitTransition = { slideOutOfContainer(AnimatedContentTransitionScope.SlideDirection.End) }
) {
    // destination
}

@HiltViewModel
class ProductViewModel @Inject constructor(
    private val repository: ProductRepository,
    savedStateHandle: SavedStateHandle
) : ViewModel() {
    // ดึง route ที่มีชนิดจาก SavedStateHandle
    private val productId: String = savedStateHandle.toRoute<ProductDetail>().productId

    val product = repository.getProduct(productId)
        .stateIn(viewModelScope, SharingStarted.WhileSubscribed(5000), null)
}

class NavigationTest {
    @get:Rule
    val composeTestRule = createComposeRule()

    @Test
    fun clickingProduct_navigatesToDetail() {
        val navController = TestNavHostController(ApplicationProvider.getApplicationContext())
        navController.navigatorProvider.addNavigator(ComposeNavigator())

        composeTestRule.setContent {
            AppNavigation(navController = navController)
        }

        // นำทางไปยังรายการสินค้า
        composeTestRule.onNodeWithText("View Products").performClick()

        // คลิกสินค้าแรก
        composeTestRule.onNodeWithTag("product_item_0").performClick()

        // ตรวจสอบ destination ปัจจุบัน
        val currentRoute = navController.currentBackStackEntry?.toRoute<ProductDetail>()
        assertThat(currentRoute).isNotNull()
    }
}

@Composable
fun MainScreen(
    authState: AuthState,
    navController: NavHostController = rememberNavController()
) {
    LaunchedEffect(authState) {
        when (authState) {
            is AuthState.Authenticated -> {
                navController.navigate(Home) {
                    popUpTo(0) { inclusive = true }
                }
            }
            is AuthState.Unauthenticated -> {
                navController.navigate(AuthGraph) {
                    popUpTo(0) { inclusive = true }
                }
            }
            else -> { /* กำลังโหลด ไม่ทำอะไร */ }
        }
    }

    NavHost(
        navController = navController,
        startDestination = if (authState is AuthState.Authenticated) Home else AuthGraph
    ) {
        authNavGraph(navController)
        composable<Home> { HomeScreen() }
    }
}

NavHost(
    navController = navController,
    startDestination = "home"  // Route แบบ string เก่า
) {
    // Destination แบบ string เก่า
    composable("home") {
        HomeScreen(onNavigateToProduct = { id ->
            navController.navigate(ProductDetail(id))  // การนำทางแบบ type-safe ใหม่
        })
    }

    // Destination แบบ type-safe ใหม่
    composable<ProductDetail> { backStackEntry ->
        val route: ProductDetail = backStackEntry.toRoute()
        ProductDetailScreen(productId = route.productId)
    }
}