IssueTracker

Component used: ViewPager2

Version used: ViewPager2 1.1.0-alpha01, Fragment 1.4.0-alpha03

Devices/Android versions reproduced on: LGE LM-X525 running Android 10

My app, Muzei uses a ViewPager2 with just two tabs on just one screen. I am using the "Fragment StrictMode" feature introduced in Fragment 1.4.0-alpha01 to detect Fragment reuse (i.e., adding a Fragment instance that was previous removed from the FragmentManager) and hooked that up to non-fatal crash reporting. I got two reports from one device that this was being violated by ViewPager2:

Non-fatal Exception: androidx.fragment.app.strictmode.FragmentReuseViolation: Attempting to reuse fragment EffectsScreenFragment{e9f23e4} (b74813a6-11c9-4f9c-807c-47d5095919eb tag=f0) with previous ID 6a08d652-13f3-4522-b52c-14bd7064feb9
       at androidx.fragment.app.strictmode.FragmentStrictMode.onFragmentReuse(FragmentStrictMode.java:296)
       at androidx.fragment.app.FragmentManager.addFragment(FragmentManager.java:1365)
       at androidx.fragment.app.BackStackRecord.executeOps(BackStackRecord.java:387)
       at androidx.fragment.app.FragmentManager.executeOps(FragmentManager.java:1856)
       at androidx.fragment.app.FragmentManager.executeOpsTogether(FragmentManager.java:1764)
       at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:1708)
       at androidx.fragment.app.FragmentManager.execSingleAction(FragmentManager.java:1620)
       at androidx.fragment.app.BackStackRecord.commitNow(BackStackRecord.java:317)
       at androidx.viewpager2.adapter.FragmentStateAdapter.placeFragmentInViewHolder(FragmentStateAdapter.java:353)
       at androidx.viewpager2.adapter.FragmentStateAdapter.onViewAttachedToWindow(FragmentStateAdapter.java:284)
       at androidx.viewpager2.adapter.FragmentStateAdapter.onViewAttachedToWindow(FragmentStateAdapter.java:72)
       at androidx.recyclerview.widget.RecyclerView.dispatchChildAttached(RecyclerView.java:7867)
       at androidx.recyclerview.widget.RecyclerView$5.addView(RecyclerView.java:893)
       at androidx.recyclerview.widget.ChildHelper.addView(ChildHelper.java:107)
       at androidx.recyclerview.widget.RecyclerView$LayoutManager.addViewInt(RecyclerView.java:8902)
       at androidx.recyclerview.widget.RecyclerView$LayoutManager.addView(RecyclerView.java:8860)
       at androidx.recyclerview.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1647)
       at androidx.recyclerview.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1591)
       at androidx.recyclerview.widget.LinearLayoutManager.scrollBy(LinearLayoutManager.java:1395)
       at androidx.recyclerview.widget.LinearLayoutManager.scrollHorizontallyBy(LinearLayoutManager.java:1124)
       at androidx.recyclerview.widget.RecyclerView.scrollStep(RecyclerView.java:1969)
       at androidx.recyclerview.widget.RecyclerView$SmoothScroller.onAnimation(RecyclerView.java:12316)
       at androidx.recyclerview.widget.RecyclerView$ViewFlinger.run(RecyclerView.java:5564)
       at android.view.Choreographer$CallbackRecord.run(Choreographer.java:1054)
       at android.view.Choreographer.doCallbacks(Choreographer.java:877)
       at android.view.Choreographer.doFrame(Choreographer.java:807)
       at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:1039)
       at android.os.Handler.handleCallback(Handler.java:883)
       at android.os.Handler.dispatchMessage(Handler.java:100)
       at android.os.Looper.loop(Looper.java:214)
       at android.app.ActivityThread.main(ActivityThread.java:7615)
       at java.lang.reflect.Method.invoke(Method.java)
       at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:964)

Non-fatal Exception: androidx.fragment.app.strictmode.FragmentReuseViolation: Attempting to reuse fragment EffectsScreenFragment{e9f23e4} (b74813a6-11c9-4f9c-807c-47d5095919eb tag=f0) with previous ID 6a08d652-13f3-4522-b52c-14bd7064feb9
       at androidx.fragment.app.strictmode.FragmentStrictMode.onFragmentReuse(FragmentStrictMode.java:296)
       at androidx.fragment.app.FragmentTransaction.doAddOp(FragmentTransaction.java:299)
       at androidx.fragment.app.BackStackRecord.doAddOp(BackStackRecord.java:195)
       at androidx.fragment.app.FragmentTransaction.add(FragmentTransaction.java:224)
       at androidx.viewpager2.adapter.FragmentStateAdapter.placeFragmentInViewHolder(FragmentStateAdapter.java:351)
       at androidx.viewpager2.adapter.FragmentStateAdapter.onViewAttachedToWindow(FragmentStateAdapter.java:284)
       at androidx.viewpager2.adapter.FragmentStateAdapter.onViewAttachedToWindow(FragmentStateAdapter.java:72)
       at androidx.recyclerview.widget.RecyclerView.dispatchChildAttached(RecyclerView.java:7867)
       at androidx.recyclerview.widget.RecyclerView$5.addView(RecyclerView.java:893)
       at androidx.recyclerview.widget.ChildHelper.addView(ChildHelper.java:107)
       at androidx.recyclerview.widget.RecyclerView$LayoutManager.addViewInt(RecyclerView.java:8902)
       at androidx.recyclerview.widget.RecyclerView$LayoutManager.addView(RecyclerView.java:8860)
       at androidx.recyclerview.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1647)
       at androidx.recyclerview.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1591)
       at androidx.recyclerview.widget.LinearLayoutManager.scrollBy(LinearLayoutManager.java:1395)
       at androidx.recyclerview.widget.LinearLayoutManager.scrollHorizontallyBy(LinearLayoutManager.java:1124)
       at androidx.recyclerview.widget.RecyclerView.scrollStep(RecyclerView.java:1969)
       at androidx.recyclerview.widget.RecyclerView$SmoothScroller.onAnimation(RecyclerView.java:12316)
       at androidx.recyclerview.widget.RecyclerView$ViewFlinger.run(RecyclerView.java:5564)
       at android.view.Choreographer$CallbackRecord.run(Choreographer.java:1054)
       at android.view.Choreographer.doCallbacks(Choreographer.java:877)
       at android.view.Choreographer.doFrame(Choreographer.java:807)
       at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:1039)
       at android.os.Handler.handleCallback(Handler.java:883)
       at android.os.Handler.dispatchMessage(Handler.java:100)
       at android.os.Looper.loop(Looper.java:214)
       at android.app.ActivityThread.main(ActivityThread.java:7615)
       at java.lang.reflect.Method.invoke(Method.java)
       at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:964)

From the looks of these, it looks like these happened back to back (in the same second, at the very least, if not just one frame apart from each other).

I cannot seem to reproduce this myself.