hey! About navigation component… I can’t use popUpTo with a String (route) in nav-alpha06/compose-al...

# compose

[Jordi Saumell]

hey! About navigation component… I can’t use popUpTo with a String (route) in nav-alpha06/compose-alpha11.
If I write popUpTo AS shows both options (the one that accepts id:Int and the one that accepts route:String… but then it only accepts the Int version. And in the NavOptionsBuilder there is only the id:Int version, which makes sense with AS not compiling with a String…
How do I use popUpTo with the route?

[KD]

You’d have to manually import it. Android studio imports the wrong one.

[Jordi Saumell]

I thought so, but was not able to find it. How can I find its import?

[KD]

Wait are you talking about the navigate() function?

[KD]

i’m not seeing any popUpTo that supports a string

[Jordi Saumell]

navController.navigate(path) { popUpTo }

[KD]

and the variable path is in question correct?

[KD]

you want to pass path as a string rather than int?

[Jordi Saumell]

I already pass path as String and it works fine. But then in popUpTo I would also like to pass a String and am only able to pass an Int

[KD]

I dont think you can pass a String . In my opinion, it only takes a @IdRes Int value.

[KD]

im using alpha11 as well. unless i’m missing something.

[KD]

What you can do is reach into the graph itself like below:

navController.navigate(bottomNavigationitem.route) {
                                    popUpTo = navController.graph.startDestination
                                    launchSingleTop = true
                                }

[Jordi Saumell]

in the (old) docs it shows how to pass a string.
But more importantly, if all our destinations are build with strings in compose, it makes sense that we would pass a String, doesn’t it?

[Jordi Saumell]

With the graph I do not see how to find a non-start destination to fetch its id

[KD]

graph does have it function in its definition to search via deeplink:

DeepLinkMatch matchDeepLink(@NonNull NavDeepLinkRequest request) {
        // First search through any deep links directly added to this NavGraph
        DeepLinkMatch bestMatch = super.matchDeepLink(request);
        // Then search through all child destinations for a matching deep link
        for (NavDestination child : this) {
            DeepLinkMatch childBestMatch = child.matchDeepLink(request);
            if (childBestMatch != null && (bestMatch == null
                    || childBestMatch.compareTo(bestMatch) > 0)) {
                bestMatch = childBestMatch;
            }
        }
        return bestMatch;
    }

[KD]

But let me see why string cant be passed

[KD]

Ahh this is what that String version does:

fun NavOptionsBuilder.popUpTo(route: String, popUpToBuilder: PopUpToBuilder.() -> Unit) {
    popUpTo(createRoute(route).hashCode(), popUpToBuilder)
}

[KD]

createRoute simply appends the route and returns the string

internal fun createRoute(route: String) = "<android-app://androidx.navigation.compose/$route>"

[KD]

which then gets converted to an Int via hashCode

[Jordi Saumell]

humm ok. But it does not make sense that we have to do that manually…
There must be a way to get the conversion, mustn’t it?

[KD]

@Ian Lake i’m not quite sure what’s happening here 😅

internal fun createRoute(route: String) = "<android-app://androidx.navigation.compose/$route>"

either the popUpTo function that takes a String argument and a lambda is deprecated or somehow the navbackStack assigned this randomly generated Int via hashCode() to the respective composable entry?

[KD]

@Jordi Saumell popUpTo always takes an Int. Even the String is being converted to an Int. The question is, how does this String gets matched to the correct composable .

[Ian Lake]

if you have import androidx.navigation.compose.popUpTo, you can pass a route to popUpTo , not just an Int. That route needs to exactly match the route you've used when constructing your composable in your NavHost

[Ian Lake]

That's the whole reason the extension function exists 🙂

[KD]

But that extension function converts this String into an Int no? via

createRoute(route: String) = "<android-app://androidx.navigation.compose/$route>"

[Ian Lake]

That's an implementation detail on how routes work with Navigation Compose right now, yes

[KD]

Wait i get it, it just clicked 🤦‍♂️ . The Int after hashing would point to that destination.

[Ian Lake]

Yep, you shouldn't ever have to think about that mapping - the extension functions we provide allow you to work solely in the route land

[Jordi Saumell]

thank you @Ian Lake! and since we are at it why do I need to provide the popUpToBuilder? I see it is used for setting inclusive (not sure if anything else, but if the default to false is Ok..?

[KD]

Gotcha. I was wondering how that Int generated via hash would match correctly. But that’s an implementation detail.

[Jordi Saumell]

oh and also, how do I find those extensions when AS doesn’t autocomplete them? in this case I could even see it and press intro on it, but it wouldn’t import it

[Ian Lake]

Yeah, if false is fine, then you don't need to add anything in popUpTo's trailing lambda.

[Jordi Saumell]

and… I’m not able to get it to work 😅
I go A -> B -> C -> D -> (B with popUpTo B) and pressing back takes me to C. Not sure if I’m thinking wrong about it but back should take me to B, right?

[Jordi Saumell]

A, B and C are part of bottom nav. And C and D are in another graph. I think it should not affect, maybe I’m wrong

[KD]

I thinks its IDE being finicky and not importing properly yet. I simply manually import.

[Ian Lake]

Yeah, known issue with Studio and imports of the same name as a member function (despite them having different parameters), please star https://issuetracker.google.com/issues/172834438

[KD]

@Jordi Saumell Dont think you should keep A,B, C in backstack, given they are primary destinations at the bottom navigation.

A good idea as suggested by the google docs would be anytime a primary destination is reached, to popbackstack upto the starting destination and then adding this new destination to backstack.

onClick = {
                        navController.navigate(screen.route) {
                            // Pop up to the start destination of the graph to
                            // avoid building up a large stack of destinations
                            // on the back stack as users select items
                            popUpTo = navController.graph.startDestination
                            // Avoid multiple copies of the same destination when
                            // reselecting the same item
                            launchSingleTop = true
                        }
                    }

[Ian Lake]

The most important part is that your route strings match exactly. If you had composable("profile"), it should be popUpTo("profile"), same with composable("profile/{userId}") and popUpTo("profile/{userId}")

[KD]

Yea otherwise that String.hashCode() will generate a different Int. Btw where is that implementation 👀 ?

[Jordi Saumell]

yes, I’ve build constants to make sure I always use the same string, and in this case there aren’t event parameters, so I couldn’t get them wrong because of that

[Jordi Saumell]

@KD with your comment now I’m not sure if B should stay in the backstack or not, I thought so...
But even if it didn’t stay in the backstack C should still be removed if I use popUpTo, shouldn’t it? So it should go to the start destination (which is A)

[Ian Lake]

If B isn't on the back stack, popUpTo(B) does nothing

[Jordi Saumell]

ok, then I suppose that will be the problem. And are top destinations (bottom bar) not supposed to be in the backstack? I thought so

[KD]

This back stack :A -> B -> C -> D -> (B with popUpTo B) should lead you to A. Maybe check your code could be a bug.

[Ian Lake]

Only the start destination as per the docs: https://developer.android.com/jetpack/compose/navigation#bottom-nav

[Ian Lake]

So A should remain on the stack, but once you switch to C, B would be popped

[Ian Lake]

(similarly, when you switched from C to B, C would be popped)

[Jordi Saumell]

ok, thank you! 🙂
doing popUpTo startDestination does remove C and D. So the issue was because of B not being in the backstack as you said, and then popUpTo doing nothing

[Deepak Gahlot]

@Jordi Saumell How did you solve that int issue that needs to be passed into popUpto()

[Ian Lake]

popUpTo also has an extension that takes a route - make sure to import that one