java.lang.IllegalStateException: уже добавлено

Question

Недавно мое приложение испытывало следующие сбои:

Fatal Exception: java.lang.RuntimeException: Unable to start activity ComponentInfo{com.xxx/com.xxx.MapsActivity}: java.lang.IllegalStateException: Already added!
           at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3108)
           at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3251)
           at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
           at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
           at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
           at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1948)
           at android.os.Handler.dispatchMessage(Handler.java:106)
           at android.os.Looper.loop(Looper.java:214)
           at android.app.ActivityThread.main(ActivityThread.java:7045)
           at java.lang.reflect.Method.invoke(Method.java)
           at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
           at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:964)

Caused by java.lang.IllegalStateException: Already added!
       at android.support.v4.app.FragmentManagerImpl.restoreAllState(FragmentManager.java:3148)
       at android.support.v4.app.FragmentController.restoreAllState(FragmentController.java:158)
       at android.support.v4.app.FragmentActivity.onCreate(FragmentActivity.java:344)
       at android.support.v7.app.AppCompatActivity.onCreate(AppCompatActivity.java:85)
       at com.xxx.MapsActivity.onCreate(MapsActivity.java:15) - where it crashes in MY code
       at android.app.Activity.performCreate(Activity.java:7327)
       at android.app.Activity.performCreate(Activity.java:7318)
       at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1271)
       at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3088)
       at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3251)
       at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
       at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
       at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
       at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1948)
       at android.os.Handler.dispatchMessage(Handler.java:106)
       at android.os.Looper.loop(Looper.java:214)
       at android.app.ActivityThread.main(ActivityThread.java:7045)
       at java.lang.reflect.Method.invoke(Method.java)
       at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:964)

Я искал эту проблему, но пока не нашел решения.Там написано «Уже добавлено!», Но я понятия не имею, что это значит ...

edit: это, вероятно, связано с ранее добавленным фрагментом.Я использую PagerAdapter, и вот код, связанный с фрагментом:

@Override
    public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_map, container, false);
        SupportMapFragment mapFragment = (SupportMapFragment) getChildFragmentManager().findFragmentById(R.id.map);
        if (mapFragment != null) {
            while (getFragmentManager() == null) {
                try {
                    Thread.sleep(500);
                }
                catch (InterruptedException e) {
                    //e.printStackTrace();
                }
            }
            FragmentTransaction ft = getFragmentManager().beginTransaction();
            ft.replace(R.id.map, mapFragment).commitAllowingStateLoss();
            mapFragment.getMapAsync(this);
        }

        return view;
    }