How to keep navigation state with Compose Destination?

Question

class BaseActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent { 
            MyTheme {
                DestinationsNavHost(
                    navGraph = NavGraphs.root,
                    startRoute = FirstScreenDestination
                )
            }
        }
    }
}

I use Compose Destination like this. When the Activity is destroyed and then restored, the navigation goes back to the very first screen. How can I save the current navigation state across activity/process death?

Answer 1

use the NavHostController

val navController = rememberNavController()
NavHost(
    navController = navController,
    startDestination = FirstScreenDestination
) {
    // your composable destinations here
}

save the state

override fun onSaveInstanceState(outState: Bundle) {
    super.onSaveInstanceState(outState)
    navController.saveState() // this is where you save the state of the navController
}

restore the state

val restoredState = savedInstanceState?.getParcelable<Bundle>("nav_state")
val navController = rememberNavController()
navController.restoreState(restoredState)

save onSaveInstanceState

outState.putParcelable("nav_state", navController.saveState())

Using NavHost with the navController:

NavHost(
    navController = navController,
    startDestination = FirstScreenDestination
) {
    // your composable destinations here
}

baseActivity

class BaseActivity : AppCompatActivity() {
   
   private lateinit var navController: NavHostController

   override fun onCreate(savedInstanceState: Bundle?) {
       super.onCreate(savedInstanceState)
       
       val restoredState = savedInstanceState?.getParcelable<Bundle>("nav_state")

       setContent {
           MyTheme {
               navController = rememberNavController()
               navController.restoreState(restoredState)

               NavHost(
                   navController = navController,
                   startDestination = FirstScreenDestination
               ) {
                   // your composable destinations here
               }
           }
       }
   }

   override fun onSaveInstanceState(outState: Bundle) {
       super.onSaveInstanceState(outState)
       outState.putParcelable("nav_state", navController.saveState())
   }
}