Android Filter a listview Attempt to invoke interface method 'int java.util.List.size()' on a null object reference -

my aim filter listview research, "whatsapp" when looking friend name. have error when try write inside search box appears if search icon pressed.

this error:

process: org.testing.an_app, pid: 15386     java.lang.nullpointerexception: attempt invoke interface method 'int java.util.list.size()' on null object reference             @ android.widget.simpleadapter.getcount(simpleadapter.java:93)             @ android.widget.adapterview.checkfocus(adapterview.java:717)             @ android.widget.adapterview$adapterdatasetobserver.oninvalidated(adapterview.java:840)             @ android.widget.abslistview$adapterdatasetobserver.oninvalidated(abslistview.java:6137)             @ android.database.datasetobservable.notifyinvalidated(datasetobservable.java:50)             @ android.widget.baseadapter.notifydatasetinvalidated(baseadapter.java:59)             @ android.widget.simpleadapter$simplefilter.publishresults(simpleadapter.java:383)             @ android.widget.filter$resultshandler.handlemessage(filter.java:282)             @ android.os.handler.dispatchmessage(handler.java:102)             @ android.os.looper.loop(looper.java:135)             @ android.app.activitythread.main(activitythread.java:5254)             @ java.lang.reflect.method.invoke(native method)             @ java.lang.reflect.method.invoke(method.java:372)             @ com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:898)             @ com.android.internal.os.zygoteinit.main(zygoteinit.java:693) 

and code create listview custom items:

import android.app.actionbar; import android.app.activity; import android.os.bundle; import android.support.v7.app.actionbaractivity; import android.text.textutils; import android.util.log; import android.view.menu; import android.view.menuinflater; import android.view.menuitem; import android.view.view; import android.widget.listadapter; import android.widget.listview; import android.widget.searchview; import android.widget.simpleadapter; import java.util.arraylist; import java.util.hashmap; import java.util.random;  public class friends_list_screen extends activity {       private searchview msearchview;     private listview listview;      @override     public void oncreate(bundle savedinstancestate) {         super.oncreate(savedinstancestate);         setcontentview(r.layout.activity_friends_list);          listview = (listview) findviewbyid(r.id.friends);          create_list();          listview.settextfilterenabled(true);      }     @override     public boolean oncreateoptionsmenu(menu menu) {          menuinflater inflater = getmenuinflater();         inflater.inflate(r.menu.friend_list_screen_menu, menu);          msearchview = (searchview) menu.finditem(r.id.search).getactionview();          if (integer.valueof(android.os.build.version.sdk) > 7) {             msearchview.setonquerytextlistener(new searchview.onquerytextlistener() {                 @override                 public boolean onquerytextsubmit(string s) {                     return false;                 }                 @override                 public boolean onquerytextchange(string s) {                     listview = (listview) findviewbyid(r.id.friends);                     simpleadapter adapter = (simpleadapter) listview.getadapter();                     if (textutils.isempty(s)) {                         adapter.getfilter().filter("");                     } else {                         adapter.getfilter().filter(s.tostring().tolowercase());                     }                     return true;                 }             });         }          final menuitem searchmi = (menuitem) menu.finditem(r.id.search);          msearchview.setonquerytextfocuschangelistener(new view.onfocuschangelistener() {             @override             public void onfocuschange(view view, boolean querytextfocused) {                 if (!querytextfocused) {                     searchmi.collapseactionview();                 }             }         });         return true;     }     private void create_list(){         arraylist<friend_obj> friend_objlist=new arraylist<friend_obj>();          friend_obj [] people={                 new friend_obj("x","b",r.drawable.profile_icon),                 new friend_obj("y", "q", r.drawable.profile_icon),                 new friend_obj("z","d",r.drawable.profile_icon),                 new friend_obj("w","x",r.drawable.profile_icon)};          random r=new random();         for(int i=0;i<100;i++){             friend_objlist.add(people[r.nextint(people.length)]);         }         arraylist<hashmap<string, object>> data=new arraylist<hashmap<string,object>>();          for(int i=0;i<friend_objlist.size();i++){             friend_obj p=friend_objlist.get(i);              hashmap<string,object> friend_objmap=new hashmap<string, object>();              friend_objmap.put("image", p.getphotores());             friend_objmap.put("name", p.getname());             friend_objmap.put("surname", p.getsurname());             data.add(friend_objmap);         }          string[] from={"image","name","surname"};         int[] to={r.id.personimage,r.id.personname,r.id.personsurname};          simpleadapter adapter=new simpleadapter(                 getapplicationcontext(),                 data,                 r.layout.friends_list_item,                 from,                 to);         listview.setadapter(adapter);     } } 

perhaps didn't set adapter listview?

btw - why name variable same name class type? (listview listview)