CODEWITHSUNDEEP
androidgraphandroid-navigation-graphapplication-restartnavgraph
Andrew
Andrew

Reputation: 2896

NullPointerException: null cannot be cast to non-null type kotlin.Int. When calling navController.setGraph after restarting Activity

Sometimes, the setGraph function causes a NullPointerException: null cannot be cast to non-null type kotlin.Int. It depends on how I restart the application.

When MainActivity is created, it programmatically sets the graph and start destination. Basically, it decides whether the user is logged in or not. If logged in, then it goes to HomeFragment. If not, it shows LoginFragment.

Here is my function that sets the graph and start destination:

private fun openLogin(navGraph: NavGraph, navigateToChatAutomatically: Boolean) {
        navGraph.setStartDestination(R.id.login_nav_graph)

        try {
            navController.setGraph(
                navGraph,
                bundleOf(
                    "pageCount" to 3,
                    "navigateToChatAutomatically" to navigateToChatAutomatically
                )
            )
        }catch (t: Throwable){
            //exception java.lang.NullPointerException: null cannot be cast to non-null type kotlin.Int
        }
       
    }

When I restart activity this way, activity restarts and user gets NullPointerException when setGraph is called inside openLogin function.

fun FragmentActivity.restart(){
    val intent = this.intent
    finish()
    startActivity(intent)
}

I don't know the exact reason why the exception occurs when the activity is restarted. I've only found a working solution (see the answer below). If anyone knows why this happens or maybe there's a better solution, please let me know.

Upvotes: 0

Views: 641

Answers (1)

Andrew
Andrew

Reputation: 2896

When I restart the application from scratch by restarting its process, the application restarts and setGraph works well without any exceptions.

fun FragmentActivity.rebirth(){
    ProcessPhoenix.triggerRebirth(this)
}

And this is the library I use to restart the process:

implementation("com.jakewharton:process-phoenix:2.1.2")

Upvotes: -1

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