kotlin - How to check if the current route has a parent interface using type-safe navigation in Jetpack Compose? - Stack Overflo

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My routes are defined like this:

@Serializable
sealed interface Routes {

    @Serializable
    sealed interface TopLevel: Routes {
        @Serializable
        data object Home : TopLevel
        @Serializable
        data object Journal : TopLevel
        @Serializable
        data object Meals : TopLevel
        @Serializable
        data object Workouts : TopLevel
        @Serializable
        data object Profile : TopLevel
    }

    @Serializable
    data object Onboarding : Routes
    @Serializable
    data object Settings : Routes
}

I want to check if my current route is of type Routes.TopLevel. I tried this, but my understanding is that it checks if the Route is Routes.TopLevel and not one of its derivatives.

val navHostController = rememberNavController()
val currentBackStackEntry by navHostController.currentBackStackEntryAsState()
val currentDestination = currentBackStackEntry?.destination

val isTopLevelRoute = currentDestination?.isRoute<Routes.TopLevel>() == true

// NavDestinationExt.kt
inline fun <reified T : Routes> NavDestination.isRoute(): Boolean =
    this.hierarchy.any { it.hasRoute<T>() }

My routes are defined like this:

@Serializable
sealed interface Routes {

    @Serializable
    sealed interface TopLevel: Routes {
        @Serializable
        data object Home : TopLevel
        @Serializable
        data object Journal : TopLevel
        @Serializable
        data object Meals : TopLevel
        @Serializable
        data object Workouts : TopLevel
        @Serializable
        data object Profile : TopLevel
    }

    @Serializable
    data object Onboarding : Routes
    @Serializable
    data object Settings : Routes
}

I want to check if my current route is of type Routes.TopLevel. I tried this, but my understanding is that it checks if the Route is Routes.TopLevel and not one of its derivatives.

val navHostController = rememberNavController()
val currentBackStackEntry by navHostController.currentBackStackEntryAsState()
val currentDestination = currentBackStackEntry?.destination

val isTopLevelRoute = currentDestination?.isRoute<Routes.TopLevel>() == true

// NavDestinationExt.kt
inline fun <reified T : Routes> NavDestination.isRoute(): Boolean =
    this.hierarchy.any { it.hasRoute<T>() }

• kotlin
• android-jetpack-compose
• android-jetpack-compose-navigation

Share Improve this question Follow asked Mar 28 at 16:34 mainrsmainrs 6311 silver badge55 bronze badges

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1 Answer 1

Sorted by: Reset to default 0

What you need is not possible in jetpack compose navigation.

The library doesn't store the type of passed object or class as a route.
Here is the code from Jetpack compose library:

public fun <T : Any> navigate(
        route: T,
        navOptions: NavOptions? = null,
        navigatorExtras: Navigator.Extras? = null
    ) {
        val finalRoute : String = generateRouteFilled(route)
        navigate(
            NavDeepLinkRequest.Builder.fromUri(createRoute(finalRoute).toUri()).build(),
            navOptions,
            navigatorExtras
        )
    }

the route passed as a parameter is converted to a String using generateRouteFilled function. and never used afterward.
On the other hand, when building the navgraph, only a navigator, id, and route (string) are stored.

public open class NavDestinationBuilder<out D : NavDestination>
internal constructor(
    protected val navigator: Navigator<out D>,
    @IdRes public val id: Int,
    public val route: String?
)

That ID is used to determine whether or not a route is generated using a type by getting hashcode of it's serializer. So it's impossible to retrieve the actual type.

A similar solution:

If your inner destinations (in your case, TopLevel) represents a nested graph, you can nest them inside a graph and check that the graph is in the current backstack.

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