android – Viewpager的内容在轮换时丢失了

我有一个项目,它有一个MainActivity,它托管一个片段,通过Viewpager托管另外两个片段.它在首次启动时看起来很好,但是当我旋转时,Viewpager中的两个片段都会丢失.我已经尝试将getFragmentManager更改为getChildFragmentManager,但我会得到一个非法状态异常：无法保留嵌套在其他片段中的fragements.

MainActivity.java：

import android.app.ActionBar;
import android.os.Bundle;
import android.view.MenuItem;
import android.widget.ArrayAdapter;
import android.widget.ListView;

import com.jeremyfeinstein.slidingmenu.lib.SlidingMenu;
import com.jeremyfeinstein.slidingmenu.lib.app.SlidingFragmentActivity;

public class MainActivity extends SlidingFragmentActivity {
@TargetApi(11)
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    setContentView(R.layout.activity_main);
    getSupportFragmentManager()
    .beginTransaction()
    .replace(R.id.mainContentFrame,new WorkOutsContainerFrag())
    .commit();


     setBehindContentView(R.layout.menu);

     ActionBar actionBar = getActionBar();

        populate();

       SlidingMenu menu = getSlidingMenu();

        menu.setMode(SlidingMenu.LEFT);
        menu.setShadowWidthRes(R.dimen.shadow_width);
        menu.setShadowDrawable(R.drawable.shadow);
        menu.setBehindWidthRes(R.dimen.slidingmenu_offset);
        menu.setFadeDegree(0.35f);
        menu.setTouchModeAbove(SlidingMenu.TOUCHMODE_FULLSCREEN);
        menu.setSlidingEnabled(false);
        setSlidingActionBarEnabled(true);

        actionBar.setdisplayHomeAsUpEnabled(true);



    }


    @Override
    public boolean onoptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
        case android.R.id.home:
            toggle();
            return true;
        default:
            return super.onoptionsItemSelected(item);
        }
    }

    private void populate() {

        ListView lv = (ListView) findViewById(R.id.listView1);
        String[] values = new String[] { "Workouts","information","Ladders"};
        ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1,android.R.id.text1,values);
        lv.setAdapter(adapter);


    }

}

WorkoutsContainerFrag.java：

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.util.TypedValue;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import com.astuetz.PagerSlidingTabStrip;

public class WorkOutsContainerFrag extends Fragment {

private PagerSlidingTabStrip tabs;
private ViewPager pager;
private WorkoutsPagerAdapter adapter;

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

    setRetainInstance(true);

    tabs = (PagerSlidingTabStrip) view.findViewById(R.id.workoutstabs);
    pager = (ViewPager) view.findViewById(R.id.workoutspager);
    adapter = new WorkoutsPagerAdapter(getFragmentManager());

    pager.setAdapter(adapter);

    final int pageMargin = (int)  TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP,4,getResources()
            .getdisplayMetrics());
    pager.setPageMargin(pageMargin);

    tabs.setViewPager(pager);

    return view;

}

private GymWorkoutsFragment gymWorkoutsFragment;
private OCWorkoutsFragment ocWorkoutsFragment;

public class WorkoutsPagerAdapter extends FragmentPagerAdapter {

    private final String[] TITLES = {"Gym Workouts","OC Workouts"};

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


    @Override
    public CharSequence getPageTitle(int position) {
        return TITLES[position];
    }

    @Override
    public int getCount() {
        return TITLES.length;
    }

    @Override
    public Fragment getItem(int position) {
        switch (position) {
        case 0:
            gymWorkoutsFragment = new GymWorkoutsFragment();
            return (Fragment)gymWorkoutsFragment;

        case 1:
            ocWorkoutsFragment = new OCWorkoutsFragment();
            return (Fragment)ocWorkoutsFragment;

    }
        return null;
}

}
}