Fixed
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Comments
jg...@google.com
Hi, thanks for reporting.
Try testing the following (I think you'll find issues) with the change you're suggesting [1]
- rotation
- minimise (home button), restore
- enable "Don't keep activities" in Developer options and retest the two above.
[1]
From: mFragmentManager.beginTransaction().add(fragment, "f" + holder.getItemId()).commitNow();
To: mFragmentManager.beginTransaction().add(container.getId(), fragment, "f" + holder.getItemId()).commitNow();
Try testing the following (I think you'll find issues) with the change you're suggesting [1]
- rotation
- minimise (home button), restore
- enable "Don't keep activities" in Developer options and retest the two above.
[1]
From: mFragmentManager.beginTransaction().add(fragment, "f" + holder.getItemId()).commitNow();
To: mFragmentManager.beginTransaction().add(container.getId(), fragment, "f" + holder.getItemId()).commitNow();
jg...@google.com
Could you provide a minimal sample app for the issue you're facing? It'll help us investigate.
an...@gmail.com
Thanks for pointing out the issue with my approach, will have to play around with it a bit more. I have attached a small sample project. It has two flavours: androidx and modified. The former is the unmodified adapter where as the later is with the changes I have made earlier (have not done any further experiments to fix the issue use case you were describing).
an...@gmail.com
Modified the sample a bit to include some state saving. For a simple rotations, backgrounding and foregrounding the app I could not see anything in the first couple of runs. If you could also please give it a go and let me know what sequence of events reveal any issues I'd greatly appreciate it.
jg...@google.com
jg...@google.com
We've filed a bug on Navigation.
In the meantime, as a workaround, instead of creating a NavHostFragment directly as a page, create a regular Fragment subclass instance with a container inside it, and place NavHostFragment inside that container.
Container can be something simple, e.g. a FrameLayout with an id, e.g. generated by ViewCompat.generateId()
In the meantime, as a workaround, instead of creating a NavHostFragment directly as a page, create a regular Fragment subclass instance with a container inside it, and place NavHostFragment inside that container.
Container can be something simple, e.g. a FrameLayout with an id, e.g. generated by ViewCompat.generateId()
il...@google.com
Note that the id on your FrameLayout should *not* use ViewCompat.generateId() as the ID needs to be stable across configuration changes. The issue filed against Navigation (https://issuetracker.google.com/issues/139421197 ) has been fixed for the upcoming Navigation 2.2.0-alpha02 - when using that version of Navigation, you wouldn't have to make any modifications to your ViewPager2 adapter and it would work with any version of ViewPager2.
Description
Would like to use an existing app layout and take benefit of offscreen screen "caching"
The issue
Currently if I attempt to use NavHostFragment in combination with ViewPager2 and FragmentStateAdapter I'll get the following runtime exception due to uninitialised containterViewId (stack trace below).
If I change FragmentStateAdapter.placeFragmentInViewHolder
From:
// { f:notAdded, v:notCreated, v:notAttached } -> add, create, attach
if (!shouldDelayFragmentTransactions()) {
scheduleViewAttach(fragment, container);
mFragmentManager.beginTransaction().add(fragment, "f" + holder.getItemId()).commitNow();
}
To:
// { f:notAdded, v:notCreated, v:notAttached } -> add, create, attach
if (!shouldDelayFragmentTransactions()) {
mFragmentManager.beginTransaction().add(container.getId(), fragment, "f" + holder.getItemId()).commitNow();
}
The issue is solved. Testing a couple of scenarios did not reveal any side effects, but as I have yet to familiarise myself with the details of the implementation I'm not sure if it will not have any negative side effects.
Happy to put up a PR for this, but would like to understand better why the fragment is being added this way in the current state of the adapter.
Stack trace:
java.lang.IllegalArgumentException: Must use non-zero containerViewId
at androidx.fragment.app.FragmentTransaction.replace(FragmentTransaction.java:223)
at androidx.fragment.app.FragmentTransaction.replace(FragmentTransaction.java:200)
at androidx.navigation.fragment.FragmentNavigator.navigate(FragmentNavigator.java:181)
at androidx.navigation.fragment.FragmentNavigator.navigate(FragmentNavigator.java:58)
at androidx.navigation.NavGraphNavigator.navigate(NavGraphNavigator.java:80)
at androidx.navigation.NavGraphNavigator.navigate(NavGraphNavigator.java:30)
at androidx.navigation.NavController.navigate(NavController.java:877)
at androidx.navigation.NavController.onGraphCreated(NavController.java:524)
at androidx.navigation.NavController.setGraph(NavController.java:482)
at androidx.navigation.NavController.setGraph(NavController.java:447)
at androidx.navigation.fragment.NavHostFragment.onCreate(NavHostFragment.java:248)
at androidx.fragment.app.Fragment.performCreate(Fragment.java:2613)
at androidx.fragment.app.FragmentManagerImpl.moveToState(FragmentManagerImpl.java:831)
at androidx.fragment.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManagerImpl.java:1228)
at androidx.fragment.app.FragmentManagerImpl.moveToState(FragmentManagerImpl.java:1293)
at androidx.fragment.app.BackStackRecord.executeOps(BackStackRecord.java:439)
at androidx.fragment.app.FragmentManagerImpl.executeOps(FragmentManagerImpl.java:2066)
at androidx.fragment.app.FragmentManagerImpl.executeOpsTogether(FragmentManagerImpl.java:1856)
at androidx.fragment.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManagerImpl.java:1811)
at androidx.fragment.app.FragmentManagerImpl.execSingleAction(FragmentManagerImpl.java:1686)
at androidx.fragment.app.BackStackRecord.commitNow(BackStackRecord.java:293)
at androidx.viewpager2.adapter.FragmentStateAdapter.placeFragmentInViewHolder(FragmentStateAdapter.java:284)
at androidx.viewpager2.adapter.FragmentStateAdapter.onViewAttachedToWindow(FragmentStateAdapter.java:222)
at androidx.viewpager2.adapter.FragmentStateAdapter.onViewAttachedToWindow(FragmentStateAdapter.java:61)
at androidx.recyclerview.widget.RecyclerView.dispatchChildAttached(RecyclerView.java:7433)
at androidx.recyclerview.widget.RecyclerView$5.addView(RecyclerView.java:862)
at androidx.recyclerview.widget.ChildHelper.addView(ChildHelper.java:107)
at androidx.recyclerview.widget.RecyclerView$LayoutManager.addViewInt(RecyclerView.java:8478)
at androidx.recyclerview.widget.RecyclerView$LayoutManager.addView(RecyclerView.java:8436)
at androidx.recyclerview.widget.RecyclerView$LayoutManager.addView(RecyclerView.java:8424)
at androidx.recyclerview.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1641)
at androidx.recyclerview.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1587)
at androidx.recyclerview.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:665)
at androidx.recyclerview.widget.RecyclerView.dispatchLayoutStep2(RecyclerView.java:4040)
at androidx.recyclerview.widget.RecyclerView.dispatchLayout(RecyclerView.java:3757)
at androidx.recyclerview.widget.RecyclerView.onLayout(RecyclerView.java:4310)