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I like use data binding and navigation graph. But after update androidx dependencies from androidx.navigation:navigation-fragment:2.0.0 on 2.2.0 application is crashed after press button "Back". Crash always after return from other fragment to previous fragment containing FragmentPagerAdapter.

in build.gradle

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])

    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'

//    This is work
//    implementation 'androidx.appcompat:appcompat:1.0.2'
//    implementation 'androidx.navigation:navigation-fragment:2.0.0'

//  This generate error after backstack
    implementation 'androidx.appcompat:appcompat:1.1.0'
    implementation 'androidx.navigation:navigation-fragment:2.2.0'
}

For see a problem and getting error, please download example from https://github.com/ABRadzh/ErrorNavigation. Otherwise it will be difficult for me to explain where the error occurs.

  1. Press on any button on any page.
  2. Press hardware "Back" button.
  3. Get error message:
2020-02-11 16:15:13.119 2429-2429/in.pagerview.navigation.databinding.onbackstack E/AndroidRuntime: FATAL EXCEPTION: main
    Process: in.pagerview.navigation.databinding.onbackstack, PID: 2429
    java.lang.IllegalStateException: The specified child already has a parent. You must call removeView() on the child's parent first.
        at android.view.ViewGroup.addViewInner(ViewGroup.java:4954)
        at android.view.ViewGroup.addView(ViewGroup.java:4785)
        at androidx.viewpager.widget.ViewPager.addView(ViewPager.java:1485)
        at android.view.ViewGroup.addView(ViewGroup.java:4725)
        at android.view.ViewGroup.addView(ViewGroup.java:4698)
        at androidx.fragment.app.FragmentStateManager.createView(FragmentStateManager.java:326)
        at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1187)
        at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1356)
        at androidx.fragment.app.FragmentManager.moveFragmentToExpectedState(FragmentManager.java:1434)
        at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1497)
        at androidx.fragment.app.FragmentManager.dispatchStateChange(FragmentManager.java:2625)
        at androidx.fragment.app.FragmentManager.dispatchActivityCreated(FragmentManager.java:2577)
        at androidx.fragment.app.Fragment.performActivityCreated(Fragment.java:2722)
        at androidx.fragment.app.FragmentStateManager.activityCreated(FragmentStateManager.java:346)
        at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1188)
        at androidx.fragment.app.FragmentManager.addAddedFragments(FragmentManager.java:2224)
        at androidx.fragment.app.FragmentManager.executeOpsTogether(FragmentManager.java:1997)
        at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:1953)
        at androidx.fragment.app.FragmentManager.execPendingActions(FragmentManager.java:1849)
        at androidx.fragment.app.FragmentManager$4.run(FragmentManager.java:413)
        at android.os.Handler.handleCallback(Handler.java:790)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6719)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:449)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)

But all code for transition fragment and data binding is generated automatically. I do not known where i must call removeView().

If you try to use old dependencies, then invert all comments in code and layouts. And popBackStack() will work correctly.

I do not found anything about this error. May be, I do something incorrect?

ARadzh
  • 23
  • 3

1 Answers1

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The solution is just to add this code to every fragment:

@Override
public void onDestroyView() {
    super.onDestroyView();
    if(binding.getRoot().getParent() != null)
        ((ViewGroup)binding.getRoot().getParent()).removeView(binding.getRoot());
}

I really recommend you to create a BaseFragment which has this code and every fragment will extends from it, so you will not have to repeat the code on every fragment class.

Alejandro M
  • 61
  • 2
  • Thank you very much! It worked! I was confused by the fact that everything used to work fine on old dependencies. I added this code, but only in the fragment that contains PagerView. As it turned out, this was not enough. For a whole month, I was stomping around. – ARadzh Feb 13 '20 at 11:40
  • 1
    Thanks, my code was hitting the same problem, although not using data binding. But I've done the same basic idea as you did to remove the offending View in my code. I've got a sneaky suspicion there's actually a nasty little bug in the Android libraries responsible for this that may be leaving old views attached to the fragment that are normally going unnoticed as the new view just sits on top it hiding the problem. – greatape Mar 02 '20 at 17:45
  • Any help, why this issue is occurring? – Ravi Rawal Mar 04 '20 at 17:27