[android] Getting the error "Java.lang.IllegalStateException Activity has been destroyed" when using tabs with ViewPager

I have an application that consists of using ActionBarSherlock in tab mode.I have 5 tabs and the content of each tab is handled using fragments. For tab2 though, I have a fragment the xml file of which holds a ViewPager element which in turn has some fragment pages. When I initially start the application the application, I am able to switch between tabs no problem but when I press on tab2 for the second time I get the error mentioned above. The main activity is as follows:

public class MainActivity extends SherlockFragmentActivity
{
    @Override
    protected void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        ActionBar actionBar = getSupportActionBar();

        ActionBar.Tab tab1 = actionBar.newTab().setText("Tab1");
        ActionBar.Tab tab3 = actionBar.newTab().setText("Tab3");
        ActionBar.Tab tab2 = actionBar.newTab().setText("Tab2");
        ActionBar.Tab tab4 = actionBar.newTab().setText("Tab4");
        ActionBar.Tab tab5 = actionBar.newTab().setText("Tab5");

        Fragment fragment1 = new Tab1();
        Fragment fragment3 = new Tab3();
        Fragment fragment2 = new Tab2();
        Fragment fragment5 = new Tab5();
        Fragment fragment4 = new Tab4();

        tab1.setTabListener(new MyTabListener(fragment1));
        tab3.setTabListener(new MyTabListener(fragment3));
        tab2.setTabListener(new MyTabListener(fragment2));
        tab5.setTabListener(new MyTabListener(fragment5));
        tab4.setTabListener(new MyTabListener(fragment4));

        actionBar.addTab(tab1);
        actionBar.addTab(tab2);
        actionBar.addTab(tab3);
        actionBar.addTab(tab4);
        actionBar.addTab(tab5); 

        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
    }

    class MyTabListener implements ActionBar.TabListener
    {
        Fragment fragment;

        public MyTabListener(Fragment fragment)
        {
            this.fragment = fragment;
        }

        @Override
        public void onTabSelected(com.actionbarsherlock.app.ActionBar.Tab tab,FragmentTransaction ft) 
        {
            ft.replace(R.id.fragment_container,fragment);
        }

        @Override
        public void onTabUnselected(com.actionbarsherlock.app.ActionBar.Tab tab,FragmentTransaction ft) 
        {

        }

        @Override
        public void onTabReselected(com.actionbarsherlock.app.ActionBar.Tab tab,FragmentTransaction ft) 
        {

        }
    }
}

The fragment class without the ViewPager is as follows:

public class Tab1 extends Fragment 
{
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState)
    {
        return inflater.inflate(R.layout.activity_tab1, container, false);
    }
}

The fragment class with the ViewPager is as follows:

public class Tab2 extends Fragment 
{
    ViewPager mViewPager;
    private MyFragmentPagerAdapter mMyFragmentPagerAdapter;  
    private static int NUMBER_OF_PAGES = 5;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState)
    {
        View view =  inflater.inflate(R.layout.activity_tab2, container, false); 
        return view;
    }

    @Override
    public void onViewCreated(View view,Bundle savedInstanceState)
    {
        super.onViewCreated(view, savedInstanceState);
        mViewPager = (ViewPager) view.findViewById(R.id.viewpager);
        mMyFragmentPagerAdapter = new MyFragmentPagerAdapter(getChildFragmentManager());  
        mViewPager.setAdapter(mMyFragmentPagerAdapter);  
    }

    private static class MyFragmentPagerAdapter extends FragmentPagerAdapter 
    {    
        public MyFragmentPagerAdapter(FragmentManager fm) 
        {  
             super(fm);  
        }  

        @Override  
        public Fragment getItem(int index) 
        {  
             return PageFragment.newInstance("My Message " + index);
        }  

        @Override  
        public int getCount() 
        {  
             return NUMBER_OF_PAGES;  
        }  
   }
}

From what I've read in different places (and please correct me if I'm wrong), this happens because the fragment manager on the second pass tries to reuse the fragments from the activity which doesn't exist anymore thus giving the error.But I'm not sure why this happens over here since I'm not using fragment activity. According to logcat the error is in the Tab2 class, onViewCreated method on the line that says mViewPager.setAdapter(mMyFragmentPagerAdapter). Any help is greatly appreciated...Thanks.

03-04 12:01:05.468: E/AndroidRuntime(2474): FATAL EXCEPTION: main
03-04 12:01:05.468: E/AndroidRuntime(2474): java.lang.IllegalStateException: Activity has been destroyed
03-04 12:01:05.468: E/AndroidRuntime(2474):     at android.support.v4.app.FragmentManagerImpl.enqueueAction(FragmentManager.java:1342)
03-04 12:01:05.468: E/AndroidRuntime(2474):     at android.support.v4.app.BackStackRecord.commitInternal(BackStackRecord.java:595)
03-04 12:01:05.468: E/AndroidRuntime(2474):     at android.support.v4.app.BackStackRecord.commitAllowingStateLoss(BackStackRecord.java:578)
03-04 12:01:05.468: E/AndroidRuntime(2474):     at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:139)
03-04 12:01:05.468: E/AndroidRuntime(2474):     at android.support.v4.view.ViewPager.populate(ViewPager.java:1011)
03-04 12:01:05.468: E/AndroidRuntime(2474):     at android.support.v4.view.ViewPager.populate(ViewPager.java:880)
03-04 12:01:05.468: E/AndroidRuntime(2474):     at android.support.v4.view.ViewPager.setAdapter(ViewPager.java:433)
03-04 12:01:05.468: E/AndroidRuntime(2474):     at com.example.tabs.Tab2.onViewCreated(Tab2.java:31)
03-04 12:01:05.468: E/AndroidRuntime(2474):     at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:925)
03-04 12:01:05.468: E/AndroidRuntime(2474):     at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1088)
03-04 12:01:05.468: E/AndroidRuntime(2474):     at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:682)
03-04 12:01:05.468: E/AndroidRuntime(2474):     at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1444)
03-04 12:01:05.468: E/AndroidRuntime(2474):     at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:429)
03-04 12:01:05.468: E/AndroidRuntime(2474):     at android.os.Handler.handleCallback(Handler.java:587)
03-04 12:01:05.468: E/AndroidRuntime(2474):     at android.os.Handler.dispatchMessage(Handler.java:92)
03-04 12:01:05.468: E/AndroidRuntime(2474):     at android.os.Looper.loop(Looper.java:123)
03-04 12:01:05.468: E/AndroidRuntime(2474):     at android.app.ActivityThread.main(ActivityThread.java:3687)
03-04 12:01:05.468: E/AndroidRuntime(2474):     at java.lang.reflect.Method.invokeNative(Native Method)
03-04 12:01:05.468: E/AndroidRuntime(2474):     at java.lang.reflect.Method.invoke(Method.java:507)
03-04 12:01:05.468: E/AndroidRuntime(2474):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:842)
03-04 12:01:05.468: E/AndroidRuntime(2474):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
03-04 12:01:05.468: E/AndroidRuntime(2474):     at dalvik.system.NativeStart.main(Native Method)

I know this is an old post, but the suggested answers didn't work on my end. I want to leave this here just in case someone will find it useful.

What i did is:

@Override
public void onResume() {
    super.onResume();
    // add all fragments
    FragmentTransaction fragmentTransaction = getChildFragmentManager().beginTransaction();
    for(Fragment fragment : fragmentPages){
        String tag = fragment.getClass().getSimpleName();
        fragmentTransaction.add(R.id.contentPanel, fragment, tag);
        if(fragmentPages.indexOf(fragment) != currentPosition){
            fragmentTransaction.hide(fragment);
        } else {
            lastTag = tag;
        }
    }
    fragmentTransaction.commit();
}

Then in:

@Override
public void onPause() {
    super.onPause();
    // remove all attached fragments
    for(Fragment fragment: fragmentPages){
        getChildFragmentManager().beginTransaction().remove(fragment).commit();
    }
}

This one drove me crazy for Xamarin.

I ran into this with a ViewPager implementation for TabLayout WITHIN a Fragment, that is itself implemented in the DrawerLayout:

 - DrawerLayout
   - DrawerFragment
     - TabLayout
     - TabViewPager
       - TabViewPagerFragments

So you have to implement the following code in your DrawerFragment. Be aware to choose the correct FragmentManager-Path. Because you might have two different FragmentManager References:

1. Android.Support.V4.App.FragmentManager
2. Android.App.FragmentManager

--> Choose the one you use. If you want to make use of the ChildFragmentManager, you had to use the class declaration Android.App.FragmentManager for your ViewPager!

Android.Support.V4.App.FragmentManager

Implement the following Method in your "Main" Fragment - in this example: DrawerFragment

public override void OnDetach() {
    base.OnDetach();
    try {
        Fragment x = this;
        var classRefProp = typeof(Fragment).GetProperty("class_ref", BindingFlags.NonPublic | BindingFlags.Static);
        IntPtr classRef = (IntPtr)classRefProp.GetValue(x);
        var field = JNIEnv.GetFieldID(classRef, "mChildFragmentManager", "Landroid/support/v4/app/FragmentManagerImpl;");
        JNIEnv.SetField(base.Handle, field, IntPtr.Zero);
    }
    catch (Exception e) {
        Log.Debug("Error", e+"");
    }
}

Android.App.FragmentManager

public class TabViewPager: Android.Support.V13.App.FragmentPagerAdapter {}

That means you had to init the ViewPager with Android.App.FragmentManager.

Implement the following Method in your "Main" Fragment - in this example: DrawerFragment

public override void OnDetach() {
    base.OnDetach();
    try {
        Fragment x = this;
        var classRefProp = typeof(Fragment).GetProperty("class_ref", BindingFlags.NonPublic | BindingFlags.Static);
        IntPtr classRef = (IntPtr)classRefProp.GetValue(x);
        var field = JNIEnv.GetFieldID(classRef, "mChildFragmentManager", "Landroid/app/FragmentManagerImpl;");
        JNIEnv.SetField(base.Handle, field, IntPtr.Zero);
    }
    catch (Exception e) {
        Log.Debug("Error", e+"");
    }
}

I encountered the same issue when calling super.onCreate() at the end of my method. The reason: attachActivity() is called in onCreate() of FragmentActivity. When overriding onCreate() and, for example, creating tabs, the Tab manager will try to switch to a fragment while not having the activity attached to the FragmentManager.

Simple solution: Move the call to super.onCreate() to the head of the function body.

In general, it seems there are loads of reasons this issue may occur. This is just another one ...

Matthias

The bug has been fixed in the latest androidx version. And the famous workaround will cause crash now. so we need not it now.

I had this issue and realized it was because I was calling setContentView(int id) twice in my Activity's onCreate

I had this error because I was using LocalBroadcastManager and I did:

unregisterReceiver(intentReloadFragmentReceiver);

instead of:

LocalBroadcastManager.getInstance(this).unregisterReceiver(intentReloadFragmentReceiver);

I had this problem and I couldn't find the solution here, so I want to share my solution in case someone else has this problem again.

I had this code:

public void finishAction() {
  onDestroy();
  finish();
}

and solved the problem by deleting the line "onDestroy();"

public void finishAction() {
  finish();
}

The reason I wrote the initial code: I know that when you execute "finish()" the activity calls "onDestroy()", but I'm using threads and I wanted to ensure that all the threads are destroyed before starting the next activity, and it looks like "finish()" is not always immediate. I need to process/reduce a lot of “Bitmap” and display big “bitmaps” and I’m working on improving the use of the memory in my app

Now I will kill the threads using a different method and I’ll execute this method from "onDestroy();" and when I think I need to kill all the threads.

public void finishAction() {
  onDestroyThreads();
  finish();
}

i found that i had a timer running in the background. when the activity is killed, yet the timer still running. in the timer finish callback i access fragment object to do some work, and here is the bug!!!! the fragment exists but the activity isn't.

if you have service of timer or any background threads, make sure to not access fragments objects.

I'm having exactly the same problem. The only workaround I've found, is to replace the fragments by a new instance, each time the tabs are changed.

ft.replace(R.id.fragment_container, Fragment.instantiate(PlayerMainActivity.this, fragment.getClass().getName()));

Not a real solution, but i haven't found a way to reuse the previous fragment instance...

I encountered the same issue and lateron found out that, I have missed call to super.onCreate( savedInstanceState ); in onCreate() of FragmentActivity.

I got the very same error when trying to access the child FragmentManager before the fragment was fully initialized (i.e. attached to the Activity or at least onCreateView() called). Else the FragmentManager gets initialized with a null Activity causing the aforementioned exception.

I force the fragment containing the child fragment to NULL in onPause and it fixes my problem

fragment = null;

Wanted to add that my problem was in an activity where I tried to make a FragmentTransaction in onCreate BEFORE I called super.onCreate(). I just moved super.onCreate() to top of function and was worked fine.