After migrating to AndroidX application crashes with Attempt to invoke androidx.fragment.app.FragmentManagerImpl.isDestroyed() on a null ref

Question

The full stack includes only android core code:

java.lang.NullPointerException: Attempt to invoke virtual method 'boolean androidx.fragment.app.FragmentManagerImpl.isDestroyed()' on a null object reference
    at androidx.fragment.app.Fragment.performDetach(Fragment.java:2844)
    at androidx.fragment.app.FragmentManagerImpl.moveToState(FragmentManagerImpl.java:1033)
    at androidx.fragment.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManagerImpl.java:1237)
    at androidx.fragment.app.BackStackRecord.executeOps(BackStackRecord.java:434)
    at androidx.fragment.app.FragmentManagerImpl.executeOps(FragmentManagerImpl.java:2075)
    at androidx.fragment.app.FragmentManagerImpl.executeOpsTogether(FragmentManagerImpl.java:1865)
    at androidx.fragment.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManagerImpl.java:1820)
    at androidx.fragment.app.FragmentManagerImpl.execPendingActions(FragmentManagerImpl.java:1726)
    at androidx.fragment.app.FragmentManagerImpl$2.run(FragmentManagerImpl.java:150)
    at android.os.Handler.handleCallback(Handler.java:873)
    at android.os.Handler.dispatchMessage(Handler.java:99)
    at android.os.Looper.loop(Looper.java:193)
    at android.app.ActivityThread.main(ActivityThread.java:6669)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)

It happens when replacing the fragment in main activity:

Runnable mPendingRunnable = new Runnable() {
            @Override
            public void run() {
                FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
                fragmentTransaction.replace(R.id.frame, fragment);
                fragmentTransaction.commitAllowingStateLoss();
            }
        };

I tried without the Runnable, but same result. The cause might be somewhere else. — Mircea Slimu
– Mircea Slimu, Commented Jun 16, 2019 at 11:46

Mircea Slimu · Accepted Answer · 2019-06-23 15:49:52Z

42

I found a piece of code in myFragment.onDetach that was causing this:

It was a workaround from Getting the error "Java.lang.IllegalStateException Activity has been destroyed" when using tabs with ViewPager

        try {
            Field childFragmentManager = Fragment.class.getDeclaredField("mChildFragmentManager");
            childFragmentManager.setAccessible(true);
            childFragmentManager.set(this, null);
        } catch (NoSuchFieldException e) {
            throw new RuntimeException(e);
        } catch (IllegalAccessException e) {
            throw new RuntimeException(e);
        }

Now, in androidx, this workaround is not needed.

edited Jun 23, 2019 at 15:49

answered Jun 16, 2019 at 12:14

Mircea Slimu

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1 Comment

mvbrenes Over a year ago

I believe this should be the accepted answer, found the same snippet in our code that was leading to this issue.

S Fitz · Accepted Answer · 2019-06-18 07:58:08Z

5

In my module's gradle, I fixed it by reverting

implementation 'androidx.appcompat:appcompat:1.1.0-beta01'

to

implementation 'androidx.appcompat:appcompat:1.1.0-alpha05'

(The above answer with the childFragmentManager stuff did not help.)

answered Jun 18, 2019 at 7:58

S Fitz

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3 Comments

mvbrenes Over a year ago

I have filed an Issue for the AppCompat library here: issuetracker.google.com/issues/136741838

justArandomUser Over a year ago

ur solution worked..but do you know what caused this problem?

dragonx Over a year ago

I ran into this, it looks like androidx.appcompat:1.0.0 does not have this problem, but androidx.appcompat:1.1.0 split out the Fragment implementation to the androidx.fragment library, and this problem shows up sometime after that.

pavel · Accepted Answer · 2019-10-01 12:45:46Z

2

I was straggling last one days about this issue and finally i found the solution. Here i am using gradle

implementation 'androidx.constraintlayout:constraintlayout:1.1.2'

and i replaced my fragment using this code.

 getActivity().getSupportFragmentManager().beginTransaction().detach(new    KiKorbo()).replace(R.id.calendar1, caldroidFragment).attach(caldroidFragment)
            .addToBackStack(null).commit();

Here KiKorbo.java was my parent fragment and i replaced caldroidFragment.

answered Oct 1, 2019 at 12:45

pavel

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Comments

Seachal · Accepted Answer · 2021-01-26 12:20:12Z

1

In my module's gradle, I fixed it by reverting

implementation 'androidx.appcompat:appcompat:1.2.5'

to

implementation 'androidx.appcompat:appcompat:1.1.0'

answered Jan 26, 2021 at 12:20

Seachal

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