androidx data binding life cycle NullPointerException

Question

I cannot seem to find the origin of this DataBinding NullPointerException. While using Android Navigation Architecture when navigating to a Fragment and navigating up again repetitively I will eventually end up with the following stack trace

java.lang.NullPointerException: Attempt to invoke direct method 'void androidx.databinding.ViewDataBinding.handleFieldChange(int, java.lang.Object, int)' on a null object reference
        at androidx.databinding.ViewDataBinding.access$800(ViewDataBinding.java:64)
        at androidx.databinding.ViewDataBinding$LiveDataListener.onChanged(ViewDataBinding.java:1592)
        at androidx.lifecycle.LiveData.considerNotify(LiveData.java:113)
        at androidx.lifecycle.LiveData.dispatchingValue(LiveData.java:126)
        at androidx.lifecycle.LiveData$ObserverWrapper.activeStateChanged(LiveData.java:424)
        at androidx.lifecycle.LiveData$LifecycleBoundObserver.onStateChanged(LiveData.java:376)
        at androidx.lifecycle.LifecycleRegistry$ObserverWithState.dispatchEvent(LifecycleRegistry.java:355)
        at androidx.lifecycle.LifecycleRegistry.forwardPass(LifecycleRegistry.java:293)
        at androidx.lifecycle.LifecycleRegistry.sync(LifecycleRegistry.java:333)
        at androidx.lifecycle.LifecycleRegistry.moveToState(LifecycleRegistry.java:138)
        at androidx.lifecycle.LifecycleRegistry.handleLifecycleEvent(LifecycleRegistry.java:124)
        at androidx.fragment.app.Fragment.performStart(Fragment.java:2485)
        at androidx.fragment.app.FragmentManagerImpl.moveToState(FragmentManager.java:1494)
        at androidx.fragment.app.FragmentManagerImpl.addAddedFragments(FragmentManager.java:2646)
        at androidx.fragment.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2416)
        at androidx.fragment.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManager.java:2372)
        at androidx.fragment.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2273)
        at androidx.fragment.app.FragmentManagerImpl$1.run(FragmentManager.java:733)
        at android.os.Handler.handleCallback(Handler.java:789)
        at android.os.Handler.dispatchMessage(Handler.java:98)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6938)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:327)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1374)

It looks like it has something to do with the LiveData lifecycle as stated in the exception. I'm guessing onPause the LiveData objects in the ViewModel are cleared for memory sake and are then for some reason accessed again.

This seems to be very random as it happens on all of our fragments but only when continuously navigating to and from that specific fragment or between different fragments in the app. We don't attempt to access LiveData objects after the fragment is paused/destroyed. I have not been able to find anyone who has experienced this problem before, and find it quite difficult to get to the root of the issue.

score 33 · Accepted Answer · answered Jan 29 '19 at 00:12

33

I encountered this same issue this morning and was glad to see I wasn't the only one.

I think I've resolved it for myself although it's a little hard to be sure as you'll know. For me it was when paging between fragments in a viewPager that I would sometimes get the error. I believe the fragments were becoming detached when they were offscreen but databinding updates were still being called. I confirmed this by setting the viewPager's offscreenPageLimit to 0 and I started getting the error far more consistently.

My solution was to replace:

binding.setLifecycleOwner(this);

With:

binding.setLifecycleOwner(getViewLifecycleOwner());

See: getViewLifecycleOwner

Get a LifecycleOwner that represents the Fragment's View lifecycle. In most cases, this mirrors the lifecycle of the Fragment itself, but in cases of detached Fragments, the lifecycle of the Fragment can be considerably longer than the lifecycle of the View itself.

I haven't encountered the error again since making this change myself, so please let me know if this fixes the issue for you. I will update my answer if I do finally get the error again, but so far I am confident that this has fixed it in my case.

answered Jan 29 '19 at 00:12

Mike Simpson

426
4
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2

THANK YOU! I lost a whole day because of this, the solution seems to have fixed it. Funny enough, in my search I actually found the answer on the developer docs but because my brain was so fried I looked over it without even giving it a thought. You really made my day sir – the-ginger-geek Jan 29 '19 at 06:33
1

Well boy am I glad I posted this answer, just had this issue again and had completely blanked the cause of it. Read through the whole question before I realised I'd been here before. – Mike Simpson Mar 14 '19 at 20:22
I've been problem free since tis answer =D – the-ginger-geek Mar 15 '19 at 10:39
2

The crash still happens for me after setting the lifecycle owner to viewLifeCycleOwner. Also happens when you sit on the screen for a long time (~ 5 minutes) not just when navigating back and forth – cren90 May 06 '19 at 21:57
@cren90 Yeah, it still happens to me when you come back to the app after it has been left in the background for a while. – Julio E. Rodríguez Cabañas May 12 '19 at 00:38
1

I think it might have been resolved: https://issuetracker.google.com/issues/122066788. – Julio E. Rodríguez Cabañas May 15 '19 at 22:51
2

@JulioE.RodríguezCabañas Looks to actually be fixed, I haven't had the issue since upgrading to 3.4.1 yesterday. – cren90 May 16 '19 at 17:18
the same happens when I use RecyclerView with Databinding, @MikeSimpson can you help? – Nurseyit Tursunkulov May 21 '19 at 18:18
how to set lifecycle owner from adapter? – Nurseyit Tursunkulov Jun 04 '19 at 05:50
I did this but still getting the error logged on Crashlytics :/ I have no idea what to do – sednanre Oct 28 '20 at 20:11

androidx data binding life cycle NullPointerException

1 Answers1