java.lang.IllegalStateException: Fragment not attached to a context

Question

I have a tablayout with a viewpager in my MainActivity.

My PagerAdapter looks like this:

public class MainActivityPagerAdapter extends PagerAdapter {

    public MainActivityPagerAdapter(FragmentManager fm, int numOfTabs) {
        super(fm, numOfTabs);
    }

    @Override
    public Fragment getItem(int position) {

        switch (position) {
            case 0:
                return new StoresFragment();
            case 1:
                return new OrdersFragment();
            default:
                return null;
        }
    }
}

I am coming back from another activity like this:

Intent intent = new Intent(context, MainActivity.class);
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(intent);
finish(); //finishAffinity();

But then I get an java.lang.IllegalStateException in one of my Fragments in the viewpager of the MainActivity.

I read many related questions and tried to solve this. It is said, that this happens when one keeps references to Fragments outside of the PagerAdapter. But I am not doing this, as you can see in my code.

Does anyone know what I am doing wrong?

Edit - Stacktrace

FATAL EXCEPTION: main
    Process: com.lifo.skipandgo, PID: 23665
    java.lang.IllegalStateException: Fragment OrdersFragment{42c2a740} not attached to a context.
    at android.support.v4.app.Fragment.requireContext(Fragment.java:614)
    at android.support.v4.app.Fragment.getResources(Fragment.java:678)
    at com.lifo.skipandgo.activities.fragments.OrdersFragment$1.results(OrdersFragment.java:111)
    at com.lifo.skipandgo.connectors.firestore.QueryResult.receivedResult(QueryResult.java:37)
    at com.lifo.skipandgo.controllers.UserController$2.onUpdate(UserController.java:88)
    at com.lifo.skipandgo.connectors.firestore.QuerySubscription.onEvent(QuerySubscription.java:59)
    at com.lifo.skipandgo.connectors.firestore.QuerySubscription.onEvent(QuerySubscription.java:18)
    at com.google.firebase.firestore.zzg.onEvent(Unknown Source)
    at com.google.firebase.firestore.g.zzh.zza(SourceFile:28)
    at com.google.firebase.firestore.g.zzi.run(Unknown Source)
    at android.os.Handler.handleCallback(Handler.java:733)
    at android.os.Handler.dispatchMessage(Handler.java:95)
    at android.os.Looper.loop(Looper.java:146)
    at android.app.ActivityThread.main(ActivityThread.java:5653)
    at java.lang.reflect.Method.invokeNative(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:515)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1291)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1107)
    at dalvik.system.NativeStart.main(Native Method)

Edit: Interesting is, that the view has defenitely loaded when the error occurs. Because the error occurs about 10-15 seconds later after the fragment is shown again. I this in my orderFragment, where the error occurs:

orders = new QueryResult<UserOrder>(UserOrder.class) {
            @Override
            public void results(List<UserOrder> results) { 
orderLoadingMessage.setBackgroundColor(getResources().getColor(R.color.green)); 
    }
}

I do this in onCreateView and this result comes about 10-15 seconds after the view loaded.

Answer 1

The problem seems to be, that your fragment is listening to some events (via UserController and QueryResult) and these are fired before the fragment is attached to context.

Try to unregister the fragment when it becomes detached and to them again after attaching (LiveData can also help with this). Another way could be to receive and store the event while detached and only process it after attaching.