Hi guys i have some issues with navigation and may...
# composea
Alexa_Gal
05/14/2021, 8:34 AMHi guys i have some issues with navigation and maybe im doing it all wrong. I have a stack app that have a bottomBar on it. All works as expected i can push from login to next screen and show the 3 screens BottomNavigationBar. My issue is that every time i change tabs. my components are recomposed eventho i have set this on the navBottomNavigationItem
launchSingleTop = truea
allan.conda
05/14/2021, 9:03 AMWhat’s your issue with recomposition? That can happen anytime.
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Alexa_Gal
05/14/2021, 9:05 AMi would like to keep the state when i change tabs, e.g in the tab num 2 i have a list of itms if i scroll to the bottom and i switch to other tab and come back to the 2nd one. i would like the app to remember that the list was scrolled to that point instead of reseting everything to initial state
Alexa_Gal
05/14/2021, 9:06 AMand that actually happens if i only have the bottomNavigation. i can change tabs and it remembers the state. but if i have an stack of screens. the bottomNavigation state wont work 😕
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allan.conda
05/14/2021, 9:08 AMI see. Retaining state is different from recomposition. If you would like to retain state, you could use a `ViewModel`or
rememberSaveableallan.conda
05/14/2021, 9:08 AMIf a recomposition resets your state, then a simple config change (like rotating device) will reset everything in your screen.
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Alexa_Gal
05/14/2021, 9:14 AMi see ill have a look to the
rememberSaveablea
allan.conda
05/14/2021, 9:17 AMAh, btw, didn’t notice you’re doing something with the Login.
The recommendations for designing navigations requiring authentication are different than your graph.
You can read the guidelines here.
https://developer.android.com/guide/navigation/navigation-conditional
allan.conda
05/14/2021, 9:18 AMAre you using compose-navigation to navigate between bottom bar screens?
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Alexa_Gal
05/14/2021, 9:18 AM😻 i didnt know about that best practice 🙂
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Alexa_Gal
05/14/2021, 9:18 AMyes, i am
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allan.conda
05/14/2021, 9:20 AMso in short for logging screen you show it conditionally for every screen that requires auth, instead of being part of the static navigation (simplifies things like deeplinks)
allan.conda
05/14/2021, 9:21 AMAnd as to why it’s recomposing (or actually, losing the state). If the destination/NavBackStackEntry is removed from the stack, then the state isn’t retained. And the bottom bar behavior is that there is only one screen at a time and it doesn’t make the stack of previous bottom bar navigations.
allan.conda
05/14/2021, 9:22 AMAlso, there is an upcoming support for multiple backstacks, which you could also use for your bottom bar navigation
allan.conda
05/14/2021, 9:22 AMa
Alexa_Gal
05/14/2021, 9:24 AMThanks Allan you are a lifesaver, i was using a lot of time to fix this and i can clearly see that i was all wrong 🙂 thanks for the links and references
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allan.conda
05/14/2021, 9:25 AMFor the googlers, feel free to correct me if I’m wrong somewhere here 😅
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Ian Lake
05/14/2021, 5:08 PMHere's the last discussion (including a few more links with more background) around login: https://kotlinlang.slack.com/archives/CJLTWPH7S/p1617812338353700?thread_ts=1617805109.343700&cid=CJLTWPH7S
Ian Lake
05/14/2021, 5:09 PMBut yes, when it comes to saving the state of each bottom nav item as you swap between them, you'll want to wait for this next release and the new APIs to save/restore state that are part of that multiple back stacks bug
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Colton Idle
05/14/2021, 9:04 PM@Alexa_Gal you only have to wait until the next release for multiple back stacks. Some of us have been waiting for 👀... way longer. 😂
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Arkadii Ivanov
05/15/2021, 12:27 PMJust in case, you may try the Decompose library, it allows to handle this case correctly.
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