listview - android how to set notifySetDataChanged() for an ArrayList -

i'm trying refresh listview contents when go activity activity. refresh contents when go further main app screen , come back.

this activity set listview , it's adapter:

public static final string id = "id"; public static final string iidd = "iidd"; private static final string desc = "description";  private appcompatdelegate delegate; cursor c; listview listfood; simpleadapter myadapter; arraylist<map<string, string>> names = new arraylist<map<string, string>>(); integer i_d; integer iddd;  @override public void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     setcontentview(r.layout.activityfood_main);      listfood = (listview) findviewbyid(r.id.listviewf);     listfood.setonitemclicklistener(viewfoodlistener);      // database read     databaseconnectorfood db = new databaseconnectorfood(this);     db.open();     c = db.getfooddata();      while(c.movetonext()) {         map<string, string> data = new hashmap<string, string>(2);         data.put("description", c.getstring(c.getcolumnindex("description")));         data.put("serving_size", c.getstring(c.getcolumnindex("serving_size")));         names.add(data);     }     db.close();      myadapter = new simpleadapter(this, names, r.layout.list_food,             new string[] {"description", "serving_size"},             new int[] {r.id.viewfoodnotesone, r.id.viewfoodnotestwo});      listfood.setadapter(myadapter); } 

i tried add under onresume() doesn't work

@override protected void onresume() {     super.onresume();      myadapter.notifydatasetchanged(); } 

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edit: followed suggestion answers below doing follow, no results:

@override protected void onresume() {     super.onresume();      databaseconnectorfood db = new databaseconnectorfood(this);     db.open();     c = db.getfooddata();      while(c.movetonext()) {         map<string, string> data = new hashmap<string, string>(2);         data.put("description", c.getstring(c.getcolumnindex("description")));         data.put("serving_size", c.getstring(c.getcolumnindex("serving_size")));         names.add(data);     }     db.close();      myadapter = new simpleadapter(this, names, r.layout.list_food,             new string[] {"description", "serving_size"},             new int[] {r.id.viewfoodnotesone, r.id.viewfoodnotestwo});      // set adapter simplecursoradapter     listfood.setadapter(myadapter);      myadapter.notifydatasetchanged(); } 

solved: added names.clear(); code on here, above everything, clear listview first @rami suggested, , works! thanks

1) refresh list, need clear data (names) reload again database.

2) onresume() method called. better performance, suggest use onactivityresult() instead, while update data childs activities.

@override protected void onactivityresult(int requestcode, int resultcode, intent data) {      // refresh list here.  } 

in case, don't forget use startactivityforresult() instead of startactivity().