Compose navigation

Compose Navigation with Typed Routes

Instructions

Use androidx.navigation:navigation-compose:2.8+ with type-safe routes powered by kotlinx.serialization. String-based routes are legacy; do not introduce them in new code.

1. Define Routes as Serializable Objects

@Serializable data object HomeRoute
@Serializable data object SettingsRoute
@Serializable data class ArticleRoute(val id: String)
@Serializable data class SearchRoute(val query: String = "", val tag: String? = null)

Apply the kotlin.plugin.serialization Gradle plugin and depend on org.jetbrains.kotlinx:kotlinx-serialization-json.

2. NavHost

@Composable
fun AppNavHost(navController: NavHostController = rememberNavController()) {
    NavHost(navController = navController, startDestination = HomeRoute) {
        composable<HomeRoute> {
            HomeRoute(
                onOpenArticle = { id -> navController.navigate(ArticleRoute(id)) },
                onOpenSettings = { navController.navigate(SettingsRoute) },
            )
        }
        composable<ArticleRoute> { backStack ->
            val args: ArticleRoute = backStack.toRoute()
            ArticleRoute(id = args.id, onBack = navController::popBackStack)
        }
        composable<SearchRoute> { backStack ->
            val args: SearchRoute = backStack.toRoute()
            SearchRoute(initialQuery = args.query, initialTag = args.tag)
        }
        composable<SettingsRoute> { SettingsRoute() }
    }
}

backStack.toRoute<T>() decodes the arguments type-safely.

3. Nested Graphs and Scopes

navigation<ProfileGraphRoute>(startDestination = ProfileOverviewRoute) {
    composable<ProfileOverviewRoute> { /* ... */ }
    composable<ProfileEditRoute> { /* ... */ }
}

Get a ViewModel scoped to the nested graph:

val parent = remember(backStack) { navController.getBackStackEntry(ProfileGraphRoute) }
val vm: ProfileGraphViewModel = hiltViewModel(parent)

4. Deep Links

composable<ArticleRoute>(
    deepLinks = listOf(navDeepLink<ArticleRoute>(basePath = "https://example.com/a")),
) { /* ... */ }

Declare matching <intent-filter> in AndroidManifest.xml:

<intent-filter android:autoVerify="true">
    <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="/a"/>
</intent-filter>

5. Passing Complex Arguments

Primitives and @Serializable classes work out of the box. For non-primitive types you don't own, provide a NavType:

val FilterNavType = object : NavType<Filter>(isNullableAllowed = false) {
    override fun put(bundle: Bundle, key: String, value: Filter) { bundle.putString(key, Json.encodeToString(value)) }
    override fun get(bundle: Bundle, key: String): Filter = Json.decodeFromString(bundle.getString(key)!!)
    override fun parseValue(value: String): Filter = Json.decodeFromString(Uri.decode(value))
    override fun serializeAsValue(value: Filter): String = Uri.encode(Json.encodeToString(value))
}

composable<SearchRoute>(typeMap = mapOf(typeOf<Filter>() to FilterNavType)) { /* ... */ }

6. Pop, Replace, Single-Top

navController.navigate(HomeRoute) {
    popUpTo(LoginRoute) { inclusive = true }
    launchSingleTop = true
}

7. Events from ViewModels

Do not hold a NavController in a ViewModel. Instead, expose events and let the composable layer navigate:

LaunchedEffect(Unit) {
    vm.events.collect { e ->
        when (e) {
            is LoginEvent.Success -> navController.navigate(HomeRoute) {
                popUpTo(LoginRoute) { inclusive = true }
            }
        }
    }
}

8. Back Handling

BackHandler(enabled = state.hasUnsaved) { showLeaveDialog = true }

Checklist

• All routes are @Serializable objects/classes — no string route templates.
• kotlinx-serialization plugin applied in the module.
• NavHost start destination is a route instance, not a string.
• Deep-link domains are verified in AndroidManifest.xml with android:autoVerify="true".
• ViewModels signal navigation via events; composables call navController.
• Nested graphs use getBackStackEntry(GraphRoute) for scoped hiltViewModel.