FriendPickerFragment Facebook Android SDK not showing anything -

i don't know what's wrong code. long know code right, still got java.lang.null.pointer in

friendpickerfragment.loaddata(false); 

i defined friendpickerfragment still, got error

friendpickerfragment = (friendpickerfragment) fragmentmanager.findfragmentbyid(r.id.friend_picker_fragment); 

here whole code , think it's same facebook sdk sample friendpicker

public class pickfriends extends fragmentactivity {  friendpickerfragment friendpickerfragment;  public static void populateparameters(intent intent, string userid, boolean multiselect, boolean showtitlebar){     intent.putextra(friendpickerfragment.user_id_bundle_key,userid);     intent.putextra(friendpickerfragment.multi_select_bundle_key, multiselect);     intent.putextra(friendpickerfragment.show_title_bar_bundle_key,showtitlebar); }  @override protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     setcontentview(r.layout.activity_pick_friends);      fragmentmanager fragmentmanager = getsupportfragmentmanager();      if(savedinstancestate == null){         final bundle args = getintent().getextras();         friendpickerfragment = new friendpickerfragment(args);         fragmentmanager.begintransaction()                 .add(r.id.friend_picker_fragment, friendpickerfragment);         //friendpickerfragment = (friendpickerfragment) fragmentmanager.findfragmentbyid(r.id.friend_picker_fragment);     } else {         friendpickerfragment = (friendpickerfragment) fragmentmanager.findfragmentbyid(r.id.friend_picker_fragment);     }      friendpickerfragment.setonerrorlistener(new pickerfragment.onerrorlistener() {         @override         public void onerror(pickerfragment<?> fragment, facebookexception error) {             pickfriends.this.onerror(error);         }     });      friendpickerfragment.setondonebuttonclickedlistener(new pickerfragment.ondonebuttonclickedlistener() {         @override         public void ondonebuttonclicked(pickerfragment<?> fragment) {             selectfriend application = (selectfriend) getapplication();             application.setselectedusers(friendpickerfragment.getselection());              setresult(result_ok,null);             finish();         }     }); }  private void onerror(exception error){     string text = "error exception";     toast toast = toast.maketext(this,text,toast.length_short);     toast.show(); }  @override protected void onstart(){     super.onstart();     friendpickerfragment.loaddata(false); }  @override public boolean oncreateoptionsmenu(menu menu) {     // inflate menu; adds items action bar if present.     getmenuinflater().inflate(r.menu.menu_pick_friends, menu);     return true; }  @override public boolean onoptionsitemselected(menuitem item) {     // handle action bar item clicks here. action bar     // automatically handle clicks on home/up button, long     // specify parent activity in androidmanifest.xml.     int id = item.getitemid();      //noinspection simplifiableifstatement     if (id == r.id.action_settings) {         return true;     }      return super.onoptionsitemselected(item); } 

}

please me. thank you