Android - NPE when using FragmentPagerAdapter and rotating device

Question

I am trying to implement an MVP architecture by following Google's sample todo app

The problem I have is that I am getting a NPE when starting my presenter in the onResume() of the fragments. This happens when I change the orientation of the device.

I have a FragmentPagerAdapter with two static fragments.

From what I understand the FragmentPagerAdapter is meant to retain the fragments when the screen is rotated which implies the fragments would retain their presenters. However the presenters are null in onResume() so there is something I am not understanding.

Here is my current FragmentPagerAdapter

public class SectionsPagerAdapter extends FragmentPagerAdapter {

    public SectionsPagerAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int position) {
        switch (position) {
            case 0:
                FragmentA fragA = FragmentA.newInstance();
                PresenterA presA = new PresenterA(fragA);
                return fragA;
            case 1:
                FragmentB fragB = FragmentB.newInstance();
                PresenterB presB = new PresenterB(fragB);
                return fragB;
        }
        return null;
    }

    @Override
    public int getCount() {
        return 2;
    }
}

Answer 1

So it turns out even with a FragmentPagerAdapter the fragment is actually destroyed after configuration changes (eg. screen is rotated), so my initial assumption was wrong. I found this out by overring and adding a print statement in the fragment's onDestroy method.

In my case in order to retain the presenter I just had to setRetainInstance(true) in the fragment's onCreate method.