在ViewPager中旋转后，选项卡内容消失了

Question

I put a FragmentTabHost into a ViewPager, but the tab content has gone after I rotate the device. The tab content will come back if I click on another tab to refresh content. Is there anything wrong in my code? Please help me know.

public class MyActivity extends FragmentActivity
{
    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        LayoutInflater inflater = getLayoutInflater();

        View tabView = inflater.inflate(R.layout.tab, null);
        FragmentTabHost tabHost = (FragmentTabHost) tabView.findViewById(android.R.id.tabhost);
        tabHost.setup(this, getSupportFragmentManager(), R.id.realtabcontent);
        tabHost.addTab(tabHost.newTabSpec("tab1").setIndicator("Tab1"), TabContent1Fragment.class, null);
        tabHost.addTab(tabHost.newTabSpec("tab2").setIndicator("Tab2"), TabContent2Fragment.class, null);

        View page2 = inflater.inflate(R.layout.page2, null);
        ViewPager viewPager = (ViewPager) findViewById(R.id.viewPager);
        List<View> list = new ArrayList<View>();
        list.add(page2);
        list.add(tabView);

        viewPager.setAdapter(new DemoPagerAdapter(list));
    }
}


public class TabContent1Fragment extends Fragment
{
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
    {
        return inflater.inflate(R.layout.tab_content_1, null);
    }
}

public class DemoPagerAdapter extends PagerAdapter
{
    private List<View> mModeViewPageList;

    public DemoPagerAdapter(List<View> modeViewPageList)
    {
       this.mModeViewPageList = modeViewPageList;
    }

    @Override
    public Object instantiateItem(ViewGroup container, int position)
    {
        container.addView(mModeViewPageList.get(position), 0);
        return mModeViewPageList.get(position);
    }

    @Override
    public void destroyItem(ViewGroup container, int position, Object object)
    {
        container.removeView(mModeViewPageList.get(position));
    }

    @Override
    public int getCount()
    {
        return mModeViewPageList.size();
    }

    @Override
    public boolean isViewFromObject(View view, Object o)
    {
        return view == o;
    }
}

Answer 1

Thanks to my friend, finally I found the reason was that I used PagerAdapter .

When device is rotated, all views will be recreated. But without extra codes for fragment management, PagerAdapter is not able to mange the state of the fragments inside views (tab content fragments in realtabcontent in my case) and the child fragment of a view will disappear after rotation.

So I should change all views for ViewPager into fragments and use FragmentPagerAdapter instead.

One more thing, it should be used getChildFragmentManager() from Fragment in onCreateView instead of getSupportFragmentManger() from FragmentActivity to manage the child fragments in a fragment.

Answer 2

I wanted to point out an important point in Light's answer. If you convert an Activity to a Fragment then you may have been using getSupportFragmentManager . When converting it, you may have changed it to getActivity().getSupportFragmentManager() . It will seemingly work until you leave and return to the fragment, and you'll find some fragments missing until you scroll the pager.

The solution is to change getActivity().getSupportFragmentManager() to getChildFragmentManager() .