Attempt to write to field ' Android.support.v4.app.FragmentManagerImpl Android.support.v4.app.Fragment.mFragmentManager ' on a null object reference

E/androidruntime:fatal Exception:main
Process:org.example.magnusluca.drawertestapp, pid:3624
Java.lang.NullPointerException: attempt to write to field ' Android.support.v4.app.FragmentManagerImpl Android.support.v4.app.Fragment.mFragmentManager ' on a null object reference
The previous code was not modified:

 Public classOrdermanagerfragmentpageradapterextendsFragmentpageradapter {PrivateFollowingResult.DataEntity.CountEntity countentity;  PublicOrdermanagerfragmentpageradapter (fragmentmanager FM, FollowingResult.DataEntity.CountEntity countentity) { Super(FM);  This. countentity =countentity; } @Override Public voidDestroyitem (ViewGroup container,intposition, Object object) {            //Super.destroyitem (container, Position, object);} @Override PublicFragment GetItem (intposition) {ordermanagerfragment Badgerefreshlistener=ordermanagerfragment. This; String Strtabtitle=Titles[position]; Switch(strtabtitle) { Case"New Order":                    returnneworderfragment.newinstance (Badgerefreshlistener);  Case"In-Trace":                    returnneworderfragment.newinstance (Badgerefreshlistener);  Case"Turn Out":                    returnneworderfragment.newinstance (Badgerefreshlistener);  CaseSold Prices:                    returnneworderfragment.newinstance (Badgerefreshlistener);  CaseLoss:                    returnneworderfragment.newinstance (Badgerefreshlistener);  CaseInvalid:                    returnneworderfragment.newinstance (Badgerefreshlistener); default:                    return null ; }} @Override PublicCharsequence Getpagetitle (intposition) {            returnTitles[position%Titles.length]; } @Override Public intGetCount () {returntitles.length; }    }

The problem occurs mainly in the red Place, the code has been modified to

return new Neworderfragment ();
Problem solving

StackOverflow above solution: Http://stackoverflow.com/questions/26822516/how-to-display-3-fragments-inside-pageviewer

Attempt to write to field ' Android.support.v4.app.FragmentManagerImpl Android.support.v4.app.Fragment.mFragmentManager ' on a null object reference