Why is Android O failing with “does not belong to

问题:

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'

    }

回答1:

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();

回答2:

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.

回答3:

I just faced the same issues in the project that I am currently working on when we moved to Android Studio 3 and upgraded the support library to version 26. All of a sudden, without changing the code, we got tons of this exception. In the end I found out the following:

Google added a new "sanity check" in the sources of the v4 Fragment Manager in January this year (not sure into what release that went) that refuses to add a fragment using a Fragment Manager, if it has a target fragment set and the target fragment cannot be found in the active fragments of the same Fragment Manager. The patch is described in detail here

Ealier versions seem to not have cared about that. Took me a few days to update all the areas in our code where fragments that were added using the Support Fragment Manager used the Child Fragment Manager for their subfragments with the parent fragment as target. Well, late penalty for writing bad code.

回答4:

I had the same case as Markus Ressel but I was using getChildFragmentManager(). I replaced that with getFragmentManager() and it resolved the issue.

UPDATE: I've now been working with childFragmentManager and have some feedback.

When dealing with inner fragments that are hosted by a fragment (so a fragment within a fragment) use the childFragmentManager. This fragment manager differs from the activities getSupportFragmentManager. The two are not the same. It's a separation of concerns.

So I've made a rule that fragments hosting child fragments will always use the childFragmentManager and things not inside host fragments can use getSupportfragmentManager.

回答5:

my app work well until upgrade target version to 27 then i face same issue when call setTargetFragment (Fragment fragment, int requestCode)

example:

chooseRegionFragment.setTargetFragment(ParentFragment.this, REQUEST_CODE_CHOOSE_REGION); 

just change to:

chooseRegionFragment.setTargetFragment(getRootParentFragment(this), REQUEST_CODE_CHOOSE_REGION);

getRootParentFragment(this) this method will find root parent of fragments for you

/** 
   * find root parent of fragment 
   */ 
  public static Fragment getRootParentFragment(Fragment fragment) { 
    Fragment parent = fragment.getParentFragment(); 
    if(parent == null) 
      return fragment; 
    else 
      return getRootParentFragment(parent); 
  }