Why is Android O failing with "does not belong to this FragmentManager!"

Question

I have migrated my application to Android O in Android Studio 3

Running on an Android O emulator all my dialogFragments now fail with :-

java.lang.IllegalStateException: Fragment MyDialogFragment{43ccf50 #2 MyDialogFragment} declared target fragment SettingsFragment{ceed549 #0 id=0x7f0f0142 android:switcher:2131689794:0} that does not belong to this FragmentManager! at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1316) at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1624) at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1689) at android.support.v4.app.BackStackRecord.executeOps(BackStackRecord.java:794) at android.support.v4.app.FragmentManagerImpl.executeOps(FragmentManager.java:2470) at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2260) at android.support.v4.app.FragmentManagerImpl.optimizeAndExecuteOps(FragmentManager.java:2213) at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2122) at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:746) at android.os.Handler.handleCallback(Handler.java:769) at android.os.Handler.dispatchMessage(Handler.java:98) at android.os.Looper.loop(Looper.java:164) at android.app.ActivityThread.main(ActivityThread.java:6535) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767) 

I have made no code changes whatsoever.

What has changed in Android O that previously working DialogFragments now fail display?

Android Studio 3.0 Canary 1 Build #AI-171.4010489, built on May 15, 2017 JRE: 1.8.0_112-release-b736 x86_64 JVM: OpenJDK 64-Bit Server VM by JetBrains s.r.o Mac OS X 10.11.6      compileSdkVersion 'android-O'     buildToolsVersion "26.0.0-rc2"     AndroidManifest.xml     defaultConfig {         minSdkVersion 16         targetSdkVersion 'O'         }  compile 'com.android.support:appcompat-v7:26.0.0-beta1' compile 'com.android.support:cardview-v7:26.0.0-beta1' compile 'com.android.support:design:26.0.0-beta1'     compile 'com.android.support:percent:26.0.0-beta1'    dependencies {         classpath 'com.android.tools.build:gradle:3.0.0-alpha1'      } 

Answer 1

For me this was not only an issue on Android O but also on older versions. The oldest version I tested was API Level 16.

I was instantiating my fragments using this code:

MyFragment myFragment = MyFragment.newInstance(); myFragment.setTargetFragment(ParentFragment.this, 0); myFragment.show(getActivity().getSupportFragmentManager(), null); 

Where ParentFragment.this is a custom class extending android.support.v4.app.Fragment, MyFragment also extends this class and is a child fragment of the ParentFragment fragment (hence it's name).

I thought that I had to use a SupportFragmentManager (the getSupportFragmentManager() method) because I am using a fragment of the support package so I tried to call getActivity().getSupportFragmentManager() to get an activity reference that supported this method.

This does not seem to be the correct way though. I changed those calls to:

MyFragment myFragment = MyFragment.newInstance(); myFragment.setTargetFragment(ParentFragment.this, 0); myFragment.show(getFragmentManager(), null); 

so the fragment decides on it's own which FragmentManager to use and the error is gone now.

Hope this helps someone.

Answer 2

I had the same problem, definitely an android bug. It happens when you are showing a fragment from another fragment using it as target. As workaround you can use:

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O)     getActivity().getFragmentManager().beginTransaction().add(dialogFrag, "dialog").commit(); else     getChildFragmentManager().beginTransaction().add(dialogFrag,"dialog").commit();