Calling a method in a fragment in a FragmentStatePagerAdapter from the activity that created it

I have an activity that has a navigation drawer and a Fragment state adapter. When ever I click something in the navigation drawer I am passing that info to the mainactivity via a interface.And then I am passing that data to the main fragment which is in Fragmentstateadapter. The problem is when ever the screen rotates I get a null pointer exception for the main fragment.`

public class MainActivity extends ActionBarActivity implements RightDrawerRecyclerAdapter.Filters,
    LeftDrawerFragment.MenuSection,CommonAsyncTask.ServerData {
private static final String TAG = MainActivity.class.getSimpleName();
public MainFragment mMainFragment;
  @Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    ViewPager pager = (ViewPager) findViewById(R.id.pager);
    ScreenSlidePagerAdapter pagerAdapter = new ScreenSlidePagerAdapter(getSupportFragmentManager());
    pager.setAdapter(pagerAdapter);

}

   @Override
public void getMenuSelection(int selection) {
    Log.d(TAG,"getMenuSelection->"+selection);
        mMainFragment.getMenuSelection(selection);

}



private class ScreenSlidePagerAdapter extends FragmentStatePagerAdapter {

    public ScreenSlidePagerAdapter(FragmentManager fm) {
        super(fm);
        Log.d(TAG, "in screenslide");
    }

    @Override
    public Fragment getItem(int position) {
        if (position == 0) {
            Log.d(TAG, "in returning MainFragment");
            mMainFragment=new MainFragment();
            return mMainFragment;
        } else {
            return new MapViewFragment();
        }
    }

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

    @Override
    public CharSequence getPageTitle(int position) {
        if (position == 0) {
            return "List";
        } else {
            return "Map";
        }
    }
}}

So getMenuSelection is the method from the interface in navigation drawer. Then I have a method with the same name in my main fragment in MainFragment.So when ever I select something in the navigation drawer I can change contents in the main fragment but when ever I turn my screen a new instance of MainFragment is getting created and getItem(int position) is not getting trigged so my MainFragment object is null and now I cant pass data from my navigation drawer to main fragment.I tried making MainFragment object as static and that created problems in my MainFragment class.

So how can I get back the same MainFragment object even when the screen is turned. Or is there any better way to pass data between navigation drawer fragment and a fragment in FragmentState adapter