Hello. I'm trying to migrate my app from fragments...

# compose

[Simon]

Hello. I'm trying to migrate my app from fragments to compose. I've planned to do it fragment by fragment with a Composeview inside each, but I'm facing an issue with state restoration when using navigation component. When put on the backstack, the fragment's view is destroyed, but onSaveInstanceState is not called and there is no saveHierarchyState mechanism on ComposeView . So when a fragment's view is recreated when i pop the backstack, all scroll state of LazyColumn is lost for example. Is there a way to save this state inside fragments ? Thanks

[Andrey Kulikov]

could you please verify it still works like this on the latest version of fragments? androidx.fragment:fragment:1.3.2

[Ian Lake]

Yep, keep in mind that Navigation only depends on Fragment 1.2.X and you need Fragment 1.3.X for the proper fixes for embedding Compose in a Fragment (this particular issue should have been fixed by https://issuetracker.google.com/issues/158503763 in Fragment 1.3.0-alpha07)

[Ian Lake]

Compose no longer force upgrades your version of Fragments, so make sure you have an explicit dependency on the latest version of Fragments

[Simon]

Thanks for your answers. I'm already using the version of 1.3.2 of Fragments and the latest beta of Compose. The CompositionLocal LocalSaveableStateRegistry is indeed using FragmentViewLifecycleOwner when a DisposableSaveableStateRegistry is created.

[Andrey Kulikov]

please file a bug then

[Simon]

I've put some breakpoints to see what is happening when a fragment is put on the backstack. It seems to me that all the DisposableEffect s created when using rememberSaveable are disposed, so all the entries of the registry are removed, then the SaveableStateRegistry is unregistered from the FragmentViewLifecycleOwner and finally performSave is called, but there is nothing left to be saved

[Simon]

ok, i'm doing it now. thanks again for your help 👍

[Vadim]

Hey, did you file a bug? Can't find anything related in the tracker. I'm struggling with the same issue of losing LazyColumn scroll state on navigation.

[Ian Lake]

I would also really, really make sure you're calling setViewCompositionStrategy(ViewCompositionStrategy.DisposeOnViewTreeLifecycleDestroyed) on your `ComposeView`: https://developer.android.com/reference/kotlin/androidx/compose/ui/platform/AbstractComposeView#setviewcompositionstrategy https://developer.android.com/reference/kotlin/androidx/compose/ui/platform/ViewCompositionStrategy.DisposeOnViewTreeLifecycleDestroyed

[Simon]

Yes I did (https://issuetracker.google.com/issues/183851544), and as Ian said, setViewCompositionStrategy solved the issue

[Vadim]

Thank you! I completely missed this method 😞