Android - Viewpager and fragments, methods not working

Question

I have a ViewPager with two Fragments which I instantiate in onCreate of my FragmentActivity.

private List<Fragment> fragments = new Vector<Fragment>();

fragments.add(Fragment.instantiate(this,Frag_1.class.getName()));
fragments.add(Fragment.instantiate(this,Frag_2.class.getName()));
    this.vPagerAdapter = new Adapt(super.getSupportFragmentManager(),fragments);
    vPager = (ViewPager) super.findViewById(R.id.pager);
    vPager.setAdapter(vPagerAdapter);

My second Fragment has a method inside that I call to update my ListView - refreshList():

public class Frag_2 extends Fragment {

    private ListView list;
    private ArrayList<data> data;
    private boolean firstCreation=true;

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        this.setRetainInstance(false);
    }   

    public void onAttach(Activity activity) {
        // TODO Auto-generated method stub
        super.onAttach(activity);
    }

    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

        View view = inflater.inflate(R.layout.layout, container, false);
        list = (ListView) view.findViewById(R.id.lst);
        //this.setRetainInstance(true);
        return view;
    }


    public void refreshList(ArrayList <data> data){
        if(data!=null){
            ArrayAdapter<data> adapter = new Item_data_adapter(getActivity(),data);
            list.setAdapter(adapter);}
    }
}

Called from my FragmentActivity

//Something
Frag_2 fr = (Frag_2) vPagerAdapter.getItem(1);
if (fr.getView() != null) {
    fr.refreshList(data);
}

It works fine until I change the orientation of the screen. Correct me if I'm wrong, but I was searching for hours and I didn't find a solution or a good explanation, the FragmentActivity is created only one time and the Fragments are attached to it but the Fragments recreate on configuration changes. Now, when the orientation changes I don't get the View from onCreateso when I try to get the View from the Fragment it returns null and my refreshList() method isn't called. How can I fix this?

I'm experiencing the same problem and haven't found a solution. I'm starting to think there's a bug in `FragmentManager` or something else considering we're both experiencing this. — adneal, Sep 11 '12 at 02:29
what about your xml layout? this isn't a problem for static fragments declared in activity's layout but this isn't the case for dynamic fragments — chip, Sep 12 '12 at 01:21
@zipc Both @DLock and I are using `ViewPager`. You don't write `Fragments` in your XML in that case. — adneal, Sep 12 '12 at 01:26
I'm having the same problem. This question was asked 3 years ago, any update on this? I'm considering fixing my Activity to portrait because I'm tired of Android and it's undocumented fragment usage. I havent found anything on this and even though I retain my fragments Android still recreates the views then attaches the Activity again yet after flipping a page the fragment will have isAlive() as false. Does not make any sense to me. — breakline, Dec 20 '15 at 18:57

score 1 · Accepted Answer · answered Sep 12 '12 at 07:08

I fixed the problem this way: In the onCreate of the FragmentActivity

if(savedInstanceState!=null){
            frag1 = (frag_1) getSupportFragmentManager().getFragment(savedInstanceState, frag_1.class.getName());
            frag2 = (frag_2) getSupportFragmentManager().getFragment(savedInstanceState, frag_2.class.getName());
        }
        else{
            frag1 = (frag_1) Fragment.instantiate(this,frag_1.class.getName());
            frag2 = (frag_2) Fragment.instantiate(this,frag_2.class.getName());
        }
        fragments.add(frag1);
        fragments.add(frag2);


protected void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        getSupportFragmentManager().putFragment(outState, frag_1.class.getName(), frag1);
        getSupportFragmentManager().putFragment(outState, frag_2.class.getName(), frag2);
    }

Maybe it's not the best solution in the universe, but it looks like it works...

This does work, also adjusting the `configChanges` in the Manifest works, but I don't think these are solid solutions. I suppose this way would work in the case that you have one or two `Fragments`, but I actually have five that are being effected by this. I'm glad it works for you though. — adneal, Sep 12 '12 at 20:54

score 0 · Answer 2 · edited Dec 27 '12 at 02:35

0

When u want to refresh the List do something like this :

public void setView() {
    Frag_2 fr = (Frag_2) vPagerAdapter.getItem(1);
    fragmentManager.beginTransaction().detach(fr).commit();
    fragmentManager.beginTransaction().attach(fr).commit();
}

edited Dec 27 '12 at 02:35

Mr. S

1,469
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answered Sep 18 '12 at 13:45

ASH

2,748
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score -1 · Answer 3 · answered Sep 12 '12 at 01:34

If you are using a dynamic fragment, you need to test first to prevent creating a second instance of a fragment.

To test whether the system is re-creating the activity, check whether the Bundle argument passed to your activity’s onCreate() is null.

If it is non-null, the system is re-creating the activity. In this case, the activity automatically re-instantiates existing fragments.

If it's null you can safely instantiate your dynamic fragment. For example:

public void onCreate(Bundle savedInstanceState) {
  // ...
  if (savedInstanceState != null) {
  FragmentManager fragmentManager = getFragmentManager()
  // Or: FragmentManager fragmentManager = getSupportFragmentManager()
  FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
  ExampleFragment fragment = new ExampleFragment();
  fragmentTransaction.add(R.id.fragment_container, fragment);
  fragmentTransaction.commit();
  }
}

The Fragment class supports the onSaveInstanceState(Bundle) method (but not the onRestoreInstanceState() method) in much the same way as the Activity class.

The default implementation saves the state of all the fragment’s views that have IDs.
You can override this method to store additional fragment state information.
If the system is re-creating the fragment from a previous saved state, it provides a reference to the Bundle containing that state to the onCreate(), onCreateView(), and onActivityCreated() methods; otherwise, the argument is set to null.

If you want a detailed info, here's a good talk by Ken Jones of Marakana

This answer isn't relevant to the question. @DLock and I are not using `FragmentTransaction`, or static `Fragments` in our XML. We're using `ViewPager`, which calls for a `FragmentPagerAdapter`. — adneal, Sep 12 '12 at 01:42

Android - Viewpager and fragments, methods not working

3 Answers3