Struggling with multiple backstacks with compose routes... What would be the correct way to navigate to a destination that is in another tab? Let’s say A, J, X is the bottom bar top-level destinations, and this is the graph:

A -> B -> C
J -> K -> L
X -> Y -> Z

If app is in J, then it wants to go navigate to Y, how do I navigate to Y correctly? I just call

navController.navigate("Y")

, but then the bottom bar now behaves weirdly, tapping the J bottom bar does nothing. The bottom bar is showing because it’s logic for visibility is

currentDestination.hierarchy.any { it.route in bottomDestinations }

based on official docs and samples. Is there a better way?

You are in full control over the source of truth for what tab is selected if you don't want to use the navigation graph you are on as the source of truth (which is what the docs use)

Thank you for the quick response 🙏 I see. I do want to use the navigation graph as source of truth. If I want to respect the graph definition, the valid navigation paths for J would be: A, X (via bottom bar), and K. Is that correct? Trying to add more context, my UseCase is like a notification list with notifications containing deeplinks which can basically navigate anywhere in the app which supports deeplinks. Would explicit deeplinks via PendingIntent be the right solution here? Assuming below would be a lot more complicated as it’s going against the docs.

You are in full control over the source of truth for what tab is selected

So are you...trying to add Y to the back stack associated with A (where you are at right now)? Or are you trying to swap to the back stack of X, then show Y? Those are very different things

I imagine both could be valid use case within my context, but here let’s say I want to do the latter. Apologies if I have poor understanding how the back stack swapping works, I did try what you are describing I think, but it behaves weirdly, would you mind taking a little look at what may be wrong at my attempt at this?

navController.navigate("Y_navgraph") {
    popUpTo("J_navgraph") { // specifically J, as A seems to work (probably because it's startDestination)
        saveState = true
    }
    launchSingleTop = true
    restoreState = true
}

You most certainly want to do the exact same thing that you do for your bottom nav, including popping up to the same place

I see. I hope you bear with me for a bit more as I think I’m getting really close to what I need. All my bottom bar basically have this logic:

navController.navigate("Y_navgraph") {
    popUpTo(navController.graph.findStartDestination().id) {  // basically A
        saveState = true
    }
    launchSingleTop = true
    restoreState = true
}

Doing so I’m not sure the Up & Back button works correctly. I kind of expect it to go to

X

which is the parent of

Y

in the graph, or going back to

J

seems right as well. But it seems to go back to A (the start destination). Is this as expected or am I still missing something? It’s a bit weird to me that

Y

gets navigated to as the startDestination of the

X

tab, I kind of expected the startDestination to be there…

I think you need to be more specific about what your actual back stacks are when you start and where you want them to be when you finish. If you've never navigated to 'X' before, then the

restoreState = true

isn't going to do anything - there's nothing to restore. You've navigated to 'Y', so you get 'Y' as the only destination on that stack, exactly what you told NavController to do

I see! TIL about

clearBackStack(route)

which helped me understand

saveSate

better. So

saveState

saved a back stack tagged to the current route (

J

) before doing the

navigate(route) { popUpTo(…) }

operation. Then

restoreState

must be trying to restore the back stack of

navigate(X)

IIUC. And in above snippet we don’t want to restore the backstack hence we don’t set

restoreState=true

. I’m curious if

clearBackstack

here is necessary given we are not restoring `X`’s back stack anyway.

you probably still want to clear it out so that any existing

ViewModel

or saved state associated with those previous destinations is properly cleaned up

I see, do you mean that back stack remains available indefinitely and can still be accessed later even if I already navigated to

X

without restoring the state? assuming I don’t

saveState

from X again.

Yep, we talk a bit about that mental model of holding onto that stack separately in the deep dive blog post (in the context of fragments, but it works the same in Navigation): https://medium.com/androiddevelopers/multiple-back-stacks-b714d974f134

In my case, I do actually want to save the backstack (don’t want to reinit the ViewModel in X)

navController.navigate("X") {
    popUpTo(navController.graph.findStartDestination().id) {
        saveState = true
    }
    launchSingleTop = true
    restoreState = true
}
navController.navigate("Y")

And this one works nicely for me. Pressing Back from Y goes back to X, then X back to A.