java - FragmentStatePagerAdapter does not handle changes -

i having problem managing changing list of item using fragmentstatepageradapter. please check source here.

the problem when underlying list changes, , call notifydatasetchanged, adapter not rebuild it's internal list of fragments. referring code in instantiateitem:

@override public object instantiateitem(viewgroup container, int position) {     // if have item instantiated, there nothing     // do.  can happen when restoring entire pager     // saved state, fragment manager has     // taken care of restoring fragments had instantiated.     if (mfragments.size() > position) {         fragment f = mfragments.get(position);         if (f != null) {             return f;         }     } 

i believe code in comment wrong! if delete item @ position 0 in list, , call notifydatasetchanged, fragment @ position 0 should deleted. adapter has never updated position of fragments in own private list. therefore still shows old, deleted, data.

i found this answer hack relies on getitemposition being called , forcing fragment update it's views.

how possible manage fragments in changing list?

per viewpager.datasetchanged() source, uses pageradapter.getitemposition() determine new position of item after data change. default, getitemposition() returns position_unchanged, meaning never destroys , recreates items has created.

override getitemposition() return correct value if want update fragments exist in response notifydatasetchanged() call. example, returning position_none destroy every fragment , recreate them scratch (which, in cases, more work needs done if items reordering).