Hi everyone, I have a question about the new navig...

# compose-android

[Yusuf Ibragimov]

Hi everyone, I have a question about the new navigation version. I updated my navigation to the last version of 2.8.1. After that, popBackStack(Destination. SpecificScreen(id = 12)) is not working. I changed my Destination object to class and set @Serializable annotation. I don't know what the problem is. Here, popBackStack() works fine but when I want to return a specific destination that is in the back stack that isn't working. Who has experience in these situations?

[Ian Lake]

If you called navigate(Destination.SpecificScreen(id = 12)) then popBackStack(Destination.SpecificScreen(id = 12)) will work. Otherwise, you would not expect it to work. Is that how you navigated to that screen?

[Yusuf Ibragimov]

I tell you my case: I have 4 screen, and first is home and I navigate second screen with parameter. From second screen I navigate to the third then the fourth. From the fourth screen, I want to popBackStack to the second screen, but the second screen takes parameters. But even when I try to popBackStack to second screen with fake params, this is not working.

[Ian Lake]

I'm not sure what you mean by fake params. It would need to match exactly if you are using the version that takes an instance of SpecificScreen

[Yusuf Ibragimov]

why we need to add params while poping back stack, for example I cannot carry parameters to any upcoming screens.

[Ian Lake]

If you want to pop up to the topmost copy no matter what the params, you'd use the reified one popBackStack<Destination.SecondScreen>()

[Yusuf Ibragimov]

I didn't understand popBackStack how works, old version we didn't need parameters to return to the second screen from the fourth.

[Ian Lake]

You don't need it now either

[Ian Lake]

Instance = with params. <Class> = no params

[Yusuf Ibragimov]

How I use <Class>, I implemented navigation to my viewModels, every action comes to one navigation controller which is a listen channel for actions. In this controller class I get only intent, how can I do that?

My controller:

{
    val activity = (LocalContext.current as? Activity)
    LaunchedEffect(activity, navHostController, navigationChannel) {
        navigationChannel.receiveAsFlow().collect { intent ->
            if (activity?.isFinishing == true) return@collect

            when (intent) {
                is NavigationIntent.NavigateTo -> {
                    val curDestination = navHostController.currentDestination
                    Timber.i("WWW SS ${intent.route is Destination.Passcode}")
                    if (curDestination?.route?.contains("Passcode") == true) {
                        if (intent.route is Destination.Passcode) {
                            return@collect
                        }
                    }

                    navHostController.navigate(intent.route) {
                        launchSingleTop = intent.isSingleTop
                        //restoreState = true
                        intent.popUpToRoute?.let { popUpToRoute ->
                            popUpTo(popUpToRoute) { inclusive = intent.inclusive }
                        }
                    }
                }

                is NavigationIntent.NavigateBack -> {
                    Timber.i("www state=${navHostController.currentBackStackEntry?.lifecycle?.currentState}")
                    if (navHostController.currentBackStackEntry?.lifecycle?.currentState == Lifecycle.State.RESUMED) {
                        val route = intent.route
                        Timber.i("Lifecycle.State.RESUMED  route=${route}")
                        if (route == null) {
                            navHostController.popBackStack()
                        } else {
                            navHostController.popBackStack(route)
                        }
                    }
                }

                is NavigationIntent.ClearBackStack -> {
                    navHostController.navigate(Destination.Auth) {
                        this.popUpTo(0)
                    }
                }
            }
        }
    }
}

[Yusuf Ibragimov]

I try to popBackStack with this class:

@Serializable
data class AddMerchantToHomeScreen(val id: Long = -1, val homeId: Long) : Destination

But it ends with an error. Can you give me links to any example or instructions? @Ian Lake

[Ian Lake]

If you've forced yourself to always have instances of a class, then you probably want to use something like this if you want to ignore the parameters:

if (route == null) {
    navHostController.popBackStack()
} else {
    // Pop until we get to the destination you want, comparing only the class
    while (navHostController.currentBackStackEntry?.destination?.hasRoute(route::class) == false)
        navHostController.popBackStack()
    }
    // Then if inclusive, pop one more time
    if (intent.inclusive) {
        navHostController.popBackStack()
    }
}

[Ian Lake]

And if you say you got an error, you should really post the error message and the code you are using

[Yusuf Ibragimov]

This is a good solution, but if someone writes a destination that is not in backStack, this function ends the application. How do we handle that if this destination isn't available in backStack, then we stay on this screen.

[Yusuf Ibragimov]

Now our second problem like popBackStack problem above. While navigate to one screen, I want to set popUpToRoute, but this is again depending on parameters. Above, I sent codes of the navigation controller, how I set popUptoRoute without parameters?

[Yusuf Ibragimov]

Why I'm getting this warning?. My code works fine, but there is warning

[Ian Lake]

Correct, only the reified versions are part of the public API right now, exposing the ones that that a KClass is going to be part of Navigation 2.9 and more specifically this bug: https://issuetracker.google.com/issues/363225480

[Yusuf Ibragimov]

So what should I do now to implement my logic? @Ian Lake

[Ian Lake]

You can just suppress the warning

[Yusuf Ibragimov]

like that?

[Ian Lake]

Yep

[Ian Lake]

Then you'll be able to remove that suppression once you switch to the Nav 2.9 release that opens that API up

[Yusuf Ibragimov]

Thanks for helping.

[Yusuf Ibragimov]

Hi again @Ian Lake,
I have a new error while popping back stack. While multiple fast-clicking navigateBack give me error:

java.lang.IndexOutOfBoundsException: Index -1 out of bounds for length 1
                                                                                                    	at jdk.internal.util.Preconditions.outOfBounds(Preconditions.java:64)
                                                                                                    	at jdk.internal.util.Preconditions.outOfBoundsCheckIndex(Preconditions.java:70)
                                                                                                    	at jdk.internal.util.Preconditions.checkIndex(Preconditions.java:266)
                                                                                                    	at java.util.Objects.checkIndex(Objects.java:359)
                                                                                                    	at java.util.ArrayList.get(ArrayList.java:434)
                                                                                                    	at V2.m$j.invokeSuspend(SourceFile:43)
                                                                                                    	at Y4.a.resumeWith(SourceFile:12)
                                                                                                    	at t5.b0.run(SourceFile:99)
                                                                                                    	at m1.B.performTrampolineDispatch(SourceFile:7)
                                                                                                    	at m1.B.access$performTrampolineDispatch(SourceFile:1)
                                                                                                    	at m1.B$d.run(SourceFile:3)
                                                                                                    	at android.os.Handler.handleCallback(Handler.java:958)
                                                                                                    	at android.os.Handler.dispatchMessage(Handler.java:99)
                                                                                                    	at android.os.Looper.loopOnce(Looper.java:230)
                                                                                                    	at android.os.Looper.loop(Looper.java:319)
                                                                                                    	at android.app.ActivityThread.main(ActivityThread.java:9063)
                                                                                                    	at java.lang.reflect.Method.invoke(Native Method)
                                                                                                    	at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:588)
                                                                                                    	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1103)
                                                                                                    	Suppressed: y5.j: [m1.m0@903840f, A0.h@b55fc9c, W0{Cancelling}@33c46a5, B@6ce8a7a]
2024-11-13 10:25:04.793 19455-19481 ShellBackPreview        com.android.systemui                 E  Received BackNavigationInfo is null.

[Yusuf Ibragimov]

This is a my navigateBack logic:

is NavigationIntent.NavigateBack -> {
    val backStackEntry = navHostController.currentBackStackEntry
    if (backStackEntry?.lifecycle?.currentState == Lifecycle.State.RESUMED) {
        val route = intent.route
        if (route == null) {
            popBackStack(navHostController, activity)
        } else {
            Timber.d("TTT popBackStacked with while")
            // Pop until we get to the destination you want, comparing only the class
            while (navHostController.currentBackStackEntry?.destination?.hasRoute(route::class) == false)
                popBackStack(navHostController, activity)

            // Then if inclusive, pop one more time
            if (intent.inclusive) {
                popBackStack(navHostController, activity)
            }
        }
    }
}