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#compose
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zsperske
12/08/2020, 1:59 AMIs it normal to have nested
NavHosta
allan.conda
12/08/2020, 2:00 AMboth are valid options, depends on your use case
only the top level navigations (like the bottom nav items) should be top level
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zsperske
12/08/2020, 2:01 AMis having bottom nav at a lower level a no-no?
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Ian Lake
12/08/2020, 3:53 AMThere's very, very, very few cases where the correct solution is to nest nav hosts. Generally, just putting top level UI behind an if statement around your current destination is the better approach
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zsperske
12/08/2020, 3:53 AMdo you have a psuedo code example of that?
my root view is a list of events a user has been invited to/is attending. and once an event is selected each event has a bottom nav view to break the event up into "what are we doing/what do we need to bring/chat"
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Ian Lake
12/08/2020, 4:01 AMYou'd same the approach as any other UI, like the bottom nav in the docs: https://developer.android.com/jetpack/compose/navigation#bottom-nav
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val navBackStackEntry by navController.currentBackStackEntryAsState()
val currentRoute = navBackStackEntry?.arguments?.getString(KEY_ROUTE)
if (currentRoute != "login") {
}That seems like something you'd use tabs for FWIW
Multiple sibling screens about one subject vs bottom nav which is for separate things
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zsperske
12/08/2020, 4:03 AMyeah that's a good point
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Ian Lake
12/08/2020, 4:04 AMAnd for tabs, you'd want to be using a pager, not a nav host
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zsperske
12/08/2020, 4:04 AMi kinda see the event page as the core of the application and each "tab" offers a lot of functionality and child pages
so I may have just gotten too focused on the visual aspect of having it on the bottom
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Ian Lake
12/08/2020, 4:10 AMMaybe
But yes, on a technical level, nested nav hosts are a supported thing. For example, you could have each tab have its own nav host to navigate through multiple sub screens
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zsperske
12/08/2020, 4:13 AMyeah is that the "magic" the bottom nav provides?
i'll dig in and sort it out but thank you again for the insight! i love compose
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Manuel Vivo
12/09/2020, 9:22 AMIan, would you include scoping in the very few cases where nested nav graphs are needed? e.g. if I wanted to have a
LoginRepositoryi
Ian Lake
12/09/2020, 3:24 PMThat's appropriate for a nested graph, sure, but not a nested nav host, which was what we were talking about here.
Personally, I'd think you'd want a login source of truth to be available on any destination, be it the login destinations for writing into it or other destinations to check who the logged in user is (and redirect to login as needed as per the conditional nav guide)
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Manuel Vivo
12/09/2020, 4:43 PMFor login/user information I’d have a
UserRepositoryApplicationLoginRepositorySorry, I conflated nested graphs with nested nav hosts. I’m not quite sure what’s the difference between them to be honest. In Compose, in order to create a nav graph, you need a
NavHostMy question assumes that
navGraphViewModelsi
Ian Lake
12/09/2020, 4:58 PMAh, yeah if you have a separate
UserRepositoryCompose Navigation supports nested graphs via the
navigationm
Manuel Vivo
12/09/2020, 5:01 PMAwesome 🙂 thanks!
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allan.conda
12/10/2020, 4:56 AMOhh, I got confused with that as well. Good to know
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julioromano
05/28/2021, 12:24 PMWe’re still working on what a nice API for that would look like, but you can see an example in this answer@Ian Lake is there any update for this use case (i.e. scoping a VM to a nested nav graph)? Has a public API landed?
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hiltNavGraphViewModel()hiltViewModel()i
Ian Lake
06/01/2021, 7:03 PMval sharedViewModel = hiltViewModel(navController.getBackStackEntry("nested_nav"))🙏 1
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