Hello, question about restoring the nav graph when...

# navigation-architecture-component

[Ville Orkas]

Hello, question about restoring the nav graph when the activity is recreated from a configuration change and the nav graph has been defined using the Kotlin DSL API. The fragment restoration process seems to crash with the IllegalStateException: You must call setGraph() before calling getGraph() since the fragment is trying to access route specific parameters on its onCreate method. I located the issue here: https://android.googlesource.com/platform/frameworks/support/+/refs/heads/androidx-naviga[…]ain/java/androidx/navigation/fragment/NavHostFragment.kt


How should the system restore the graph if its not defined in XML and therefore doesn't have a graph ID? I also cannot manually set the graph myself since the NavHostFragment is inflated in the FragmentContainerView in the main activity's layout XML and I do not have access to it before the whole onCreate stack has completed and setContentView is called in the main activity.

[Ville Orkas]

Im using 2.8.9 but it has the same block of code thats handling the graph restoration

[Ville Orkas]

For anyone else wondering about this, one solution I found was to subclass the NavHostFragment and override the onCreate method such as such:

override fun onCreate(savedInstanceState: Bundle?) {
        // Initializes the parent class navHostController
        navController
        // Sets the graph after the above init has restored the back stack
        navController.graph = navController.createGraph(...) { ... }
        // Finally call the super.onCreate to complete the init process
        super.onCreate(savedInstanceState)
}