android - FragmentAdapter doesn't hold the good reference of the fragment -

i'm trying work fragment, i'm stuck issue can't solve.

i have 1 activity, holds 4 different fragment. activity, launch asynctask goes web , different data need, , send fragments.

but, when app gets killed , opened again, or when change orientation, fragments apparently recreated , custom fragmentadapter doesn't hold reference fragment.

here code of main activity.

public class mainactivity extends fragmentactivity {     mypageradapter fgsadapter;      @override     protected void oncreate(bundle savedinstancestate) {         super.oncreate(savedinstancestate);         setcontentview(r.layout.activity_main);         //...         fragmentmanager fm = super.getsupportfragmentmanager();         fgsadapter = new mypageradapter(fm,this);         viewpager mypager = (viewpager) findviewbyid(r.id.home_pannels_pager);         mypager.setadapter(fgsadapter);         mypager.setcurrentitem(0);     }     @override     protected void onresume() {         super.onresume();         ataskgetuser task = new ataskgetuser(callback, (progressbar) findviewbyid(r.id.pb_asynctask));         task.execute();     }     //what's called asynctask onpostexecute()     private void notifydatachanged() {         fgsadapter.notifyfragments(user.getitems());     }      private class mypageradapter extends fragmentpageradapter {         private list<cardfragment> fragments = new arraylist<cardfragment>();         private context c;          public mypageradapter(fragmentmanager fm, context c) {             super(fm);             cardfragment h = new habitfragment();             cardfragment d = new dailyfragment();             cardfragment t = new todofragment();             cardfragment r = new rewardfragment();             fragments.add(h);             fragments.add(d);             fragments.add(t);             fragments.add(r);         }         public int getcount() {             return fragments.size();         }          @override         public cardfragment getitem(int position) {             log.v("mainactivity_fgsmanager", "getitem()");             cardfragment f = (cardfragment) this.fragments.get(position);             return f;         }         public void notifyfragments(list<habititem> items) {             for(ontaskschanged f : fragments) {                 f.onchange(items);             }         }     } } 

so, want able do, able call onchange (an interface implemented 4 fragments), in notifydatachanged function. possible, thinking wrong way?

i got same problems once fragments, losing current fragment after every screen rotation.

i solved adding 1 line in fragment class (not in parent fragmentactivity class):

@override public view oncreateview(layoutinflater inflater, viewgroup container, bundle savedinstancestate) {     view v = inflater.inflate(r.layout.rate_fragment, container,false);      setretaininstance(true);//added not lose fragment instance during screen rotations  (...) 

for case app gets killed , opened again, not sure work though.