IssueTracker

This has been fixed internally and will be available in the Navigation 2.4.0-alpha08 release.

This will allow the creation of custom NavTypes, meaning when using the Navigation Kotlin DSL you can set your own custom argument type that defines how it should be parsed and it will work in navigation:

Given:

@Serializable
@Parcelize
data class SearchParameters(val searchQuery: String, val filters: List<String>)

A custom NavType could be written as:

class SearchParametersType : NavType<SearchParameters>(
  isNullableAllowed = false
) {
  override fun put(bundle: Bundle, key: String, value: SearchParameters) {
    bundle.putParcelable(key, value)
  }

  override fun get(bundle: Bundle, key: String): SearchParameters {
    return bundle.getParcelable(key) as SearchParameters
  }

  override fun parseValue(value: String): SearchParameters {
    return Json.decodeFromString<SearchParameters>(value)
  }

  // Only required when using Navigation 2.4.0-alpha07 and lower
  override val name = "SearchParameters"
}

This can then be used in your Kotlin DSL like any other type:

fragment<SearchFragment>(nav_routes.plant_search) {
    label = getString(R.string.plant_search_title)
    argument(nav_arguments.search_parameters) {
        type = SearchParametersType
        defaultValue = SearchParameters("cactus", emptyList())
    }
}

This example uses Kotlin Serialization to parse the value from the string, which means that Kotlin Serialization must also be used when you navigate to the destination to ensure the formats match:

val params = SearchParameters("rose", listOf("available"))
val searchArgument = Uri.encode(Json.encodeToString(params))
navController.navigate("${nav_routes.plant_search}/$searchArgument")

The custom NavType:

val params: SearchParameters? = arguments?.getParcelable(nav_arguments.search_parameters)