java - Empty List View (list fragment) -

when app running see empty layout "no data". can do? trying asynctask, doesent work. dont know do. im android newbie. may used wrong way? , trying inflate view not idea?

public class myemployefragment extends listfragment {       mytask task;     static string employer_id;     static string employer_name;     static string employer_last_name;     string str = null;     arraylist<spr_item> ret_data = null;     // имена атрибутов для map     final string attribute_id   = "p_id";     final string attribute_name = "p_name";     final string attribute_last_name = "p_last_name";     view v;     listview listview;     simpleadapter sadapter;      listview lvsimple;      @override     public void onattach(activity activity) {         super.onattach(activity);         task    = new mytask();         task.execute();      }       @override     public void onactivitycreated(bundle savedinstancestate)     {         super.onactivitycreated(savedinstancestate);      }      @override     public view oncreateview(layoutinflater inflater, viewgroup container,                                                      bundle savedinstancestate)  {          view v = inflater.inflate(r.layout.my_employe, container, false);         listview = (listview) v.findviewbyid(android.r.id.list);          // updating action bar title         getactivity().getactionbar();          // массивы данных         // string[] userid      = {employer_id};         // string[] username    = {employer_name};         // string[] userlatname = {employer_last_name};          ret_data = new  arraylist<spr_item>();         //ret_data.add(new spr_item("11","22","33"));         //ret_data.add(new spr_item("111","222","333"));         //ret_data.add(new spr_item("1111","2222","3333"));          // упаковываем данные в понятную для адаптера структуру         arraylist<map<string, object>> data = new arraylist<map<string, object>>(                 ret_data.size());         map<string, object> m;         (int = 0; < ret_data.size(); i++) {             m = new hashmap<string, object>();             m.put(attribute_id, ret_data.get(i).getid() );             m.put(attribute_name,ret_data.get(i).getname() );             m.put(attribute_last_name,ret_data.get(i).getlastname() );             data.add(m);         }          // массив имен атрибутов, из которых будут читаться данные         string[] = { attribute_id, attribute_name,attribute_last_name};         // массив id view-компонентов, в которые будут вставлять данные         int[] = { r.id.tw_employe_id ,r.id.tw_employe_name, r.id.tw_employe_last_name};          // создаем адаптер         simpleadapter sadapter = new simpleadapter(getactivity(), data, r.layout.list_item_employee,                 from, to);          // определяем список и присваиваем ему адаптер         lvsimple = (listview) v.findviewbyid(android.r.id.list);         lvsimple.setadapter(sadapter);          return v;      }      class mytask extends asynctask<void, void, void> {          @override         protected void onpreexecute() {             super.onpreexecute();          }          @override         protected void doinbackground(void... params) {                  string s = "5acacec6-752b-4eff-aa50-eebe58a52113";                 // string user_guid = myprefs.getstring("guid", "");                  httpactivity _http = new httpactivity("192.168.10.11", "80");                 _http.set_addr_protocol("/website/p/spr/spr.aspx/");                 _http.add_param("query", "spr_employee_get");                 // _http.add_param("p_guid", user_guid.tostring().trim());                 _http.add_param("p_guid", s);                 _http.send();                  ret_data = _http.getarrayparamvalue();                  //employer_name = _http.getarrayparamvalue("p_name");                 //employer_id = _http.getarrayparamvalue("p_id");                 //employer_last_name = _http.getarrayparamvalue("p_last_name");              return null;         }          @override         protected void onpostexecute(void result) {             super.onpostexecute(result);           }     }  } 

that's because when instantiate adapter data empty. should either set adapter in onpostexecute method of asynctask, or call sadapter.notifydatasetchanged adapter update views data obtained