ViewPager2 is not usable for fragment in androidx

[ChillingVan]

In androidx, we use single Acitivty with multiple fragments for page transfer. When we use NavGraph to transfer A fragment (using ViewPager2) to B fragment, and then back from B fragment to A fragment. The A fragment will crash.

Here is the crash stack.

     java.lang.IllegalStateException: Expected the adapter to be 'fresh' while restoring state.
        at androidx.viewpager2.adapter.FragmentStateAdapter.restoreState(FragmentStateAdapter.java:536)
        at androidx.viewpager2.widget.ViewPager2.restorePendingState(ViewPager2.java:350)
        at androidx.viewpager2.widget.ViewPager2.dispatchRestoreInstanceState(ViewPager2.java:375)
        at android.view.ViewGroup.dispatchRestoreInstanceState(ViewGroup.java:3886)
        at android.view.ViewGroup.dispatchRestoreInstanceState(ViewGroup.java:3886)
        at android.view.View.restoreHierarchyState(View.java:19845)
        at androidx.fragment.app.Fragment.restoreViewState(Fragment.java:573)
        at androidx.fragment.app.FragmentStateManager.restoreViewState(FragmentStateManager.java:322)
        at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1234)
        at androidx.fragment.app.FragmentManager.addAddedFragments(FragmentManager.java:2390)
        at androidx.fragment.app.FragmentManager.executeOpsTogether(FragmentManager.java:2125)
        at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:2081)
        at androidx.fragment.app.FragmentManager.execPendingActions(FragmentManager.java:1977)
        at androidx.fragment.app.FragmentManager$4.run(FragmentManager.java:417)
        at android.os.Handler.handleCallback(Handler.java:883)
        at android.os.Handler.dispatchMessage(Handler.java:100)
        at android.os.Looper.loop(Looper.java:224)
        at android.app.ActivityThread.main(ActivityThread.java:7520)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:539)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:950)

[ChillingVan]

And here is the code snippet:

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
       mViewPager2.adapter = object : FragmentStateAdapter(this) {
                override fun createFragment(position: Int): Fragment {
                    return when (position) {
                        0 -> XXX1Fragment()
                        1 -> XXX2Fragment()
                        else -> XXX1Fragment()
                    }
                }

                override fun getItemCount(): Int {
                    return 2
                }
            }
}

[mohmed1500]

[kiquenet85]

Any update on this?, i'm having exactly the same problem. is there a workaround or how can we save the state correctly ?

[ChillingVan]

Any update on this?, i'm having exactly the same problem. is there a workaround or how can we save the state correctly ?

Hey, I found a solution. Caching the view created in onCreateView can work.

override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
        if (mRootView == null) {
            mRootView = inflater.inflate(getLayout(), container, false)
        } else {
            // remove the view from its parent
            mRootView?.removeSelf()
        }
        return mRootView
    }

[netcyrax]

Having the same issue but can't get this to work.

            // remove the view from its parent
            mRootView?.removeSelf()

There's no removeSelf() in View class. Also, where do you initiate your adapter?

Thanks!

[ChillingVan]

Having the same issue but can't get this to work.

            // remove the view from its parent
            mRootView?.removeSelf()

There's no removeSelf() in View class. Also, where do you initiate your adapter?

Thanks!

Hey. The removeSelf is:

inline fun View.removeSelf(): Boolean {
    if (this.parent != null && this.parent is ViewGroup) {
        (this.parent as ViewGroup).removeView(this)
        return true
    }
    return false
}

Init adapter in onViewCreated:

        if (mViewPager.adapter == null) {
            mViewPager.adapter = YourViewPagerAdapter(childFragmentManager,
                    listOf(
                            Fragment1.newInstance(),
                            Fragment2.newInstance()
                    ))
        } else {
            mViewPager.adapter?.notifyDataSetChanged()
        }

[netcyrax]

Thanks for replying! But still getting:

    java.lang.IllegalStateException: Expected the adapter to be 'fresh' while restoring state.

YourViewPagerAdapter is a FragmentStateAdapter?

[stargeraaas]

Are you tried to create this adapter only once time? Probably, these fragments are inflating every time in viewPager, when we get onViewCreated.

[ChillingVan]

Thanks for replying! But still getting:

    java.lang.IllegalStateException: Expected the adapter to be 'fresh' while restoring state.

YourViewPagerAdapter is a FragmentStateAdapter?

No, I don't know why FragmentStateAdapter not work either. I use FragmentPagerAdapter

[ChillingVan]

Are you tried to create this adapter only once time? Probably, these fragments are inflating every time in viewPager, when we get onViewCreated.

Yes, only create once. If you create it each time, there will be some minor issues. I donot quite remember what the issues are. It maybe the lifecycle issue that the not visible page, which is next to the visible one, will call onStart again if you create the adapter each time.

[netcyrax]

Thanks for replying! But still getting:

    java.lang.IllegalStateException: Expected the adapter to be 'fresh' while restoring state.

YourViewPagerAdapter is a FragmentStateAdapter?

No, I don't know why FragmentStateAdapter not work either. I use FragmentPagerAdapter

But you cannot use FragmentPagerAdapter with ViewPager2.

Thanks again!

[ChillingVan]

Thanks for replying! But still getting:

    java.lang.IllegalStateException: Expected the adapter to be 'fresh' while restoring state.

YourViewPagerAdapter is a FragmentStateAdapter?

No, I don't know why FragmentStateAdapter not work either. I use FragmentPagerAdapter

But you cannot use FragmentPagerAdapter with ViewPager2.

Thanks again! Oh, right. I saw the code of ViewPager instead of ViewPager2.. It seems that FragmentStateAdapter does not work, and there is no solution for now. https://stackoverflow.com/questions/56646711/expected-the-adapter-to-be-fresh-while-restoring-state

[KamaniAman]

I am also facing the same issue. Did you get any solution?

as a work around, I am just setting viewpager2 adapter to null onStop

but not sure is it a proper solution

[RandGor]

@KamaniAman did your solution works well for all this time or you are facing the same problem after applying it to app?

[bshakhatreh]

it can be fixed by viewPager2.isSaveEnabled = false

https://stackoverflow.com/a/63936638/2519297