kotlinx.serialization.SerializationException: Serializer for class 'Companion' is not found: Type safe in Nested Graph Navigation

Question

I am working on a Jetpack Compose project with nested navigation, and I am following the official documentation on type-safe arguments in navigation, as explained in the Android Developer guide.

However, I am encountering the following error when I try to navigate using a data class inside a nested graph:

kotlinx.serialization.SerializationException: Serializer for class 'Companion' is not found. Please ensure that class is marked as '@Serializable' and that the serialization compiler plugin is applied.

Here is the relevant code where I define the route and the navigation:

Data class:

@Serializable
data class GroupDetail(val id: String)

Navigation logic: This is how I am navigating within my nested graph:

rootNavController.navigate(
    GroupDetail(
        id = selectedGroup.id.toString()
    )
)

Nested Graph: Here’s how I set up my nested navigation graph:

fun NavGraphBuilder.groupDetailNavGraph(rootNavController: NavHostController) {
    navigation<GroupDetailGraph>(
        startDestination = GroupDetail
    ) {
        composable<GroupDetail> { backStackEntry ->
            val group: GroupDetail = backStackEntry.toRoute()
            GroupDetailScreen(rootNavController = rootNavController)
        }
    }
}

Despite the GroupDetail class being marked as @Serializable, I keep getting the SerializationException.

What I've tried:

Verified that I am using the kotlinx.serialization plugin. Ensured that the GroupDetail class is annotated with @Serializable. Is there something I'm missing with serialization or passing arguments in the nested navigation? How can I resolve this issue?

Answer 1

I was able to resolve the issue I was facing with the kotlinx.serialization.SerializationException. After some troubleshooting, I discovered the root of the problem was related to two things:

Initialization of the route class: I needed to ensure that the route class is initialized with default or null values.

Setting the correct startDestination in the nested navigation graph: I had to use GroupDetail() as the startDestination when defining the navigation graph.

Solution Step 1: Initialize the Route Class with Default/Null Values

The first issue was with the initialization of my route. I needed to ensure that GroupDetail was initialized with null or default values when declaring the start destination in the navigation graph.

@Serializable
data class GroupDetail(val id: String? = null)

Step 2: Define Nested Graph with Correct startDestination

In my nested graph, I was missing the proper initialization of the startDestination. The solution was to ensure that GroupDetail() (with null/default values) was passed as the startDestination.

Here’s the updated navigation setup:

fun NavGraphBuilder.groupDetailNavGraph(rootNavController: NavHostController) {
    navigation<GroupDetailGraph>(
        startDestination = GroupDetail() // Ensure to use GroupDetail() here
    ) {
        composable<GroupDetail> { backStackEntry ->
            val group: GroupDetail = backStackEntry.toRoute()
            GroupDetailScreen(rootNavController = rootNavController)
        }
    }
}