android - Saving the checked list item continuously when after coming back to the activity and select -

hi new android & doing simple examples. exactly, i'm using 2 activities & contains list view on both. in first list view (activity1) empty, second list view(activity2) has list item checkbox. getting selected item 2nd activity & listed in first activity. it's fine want again click 'add' button 1st activity launches second activity select item & save. newly selected item not adding existing list value used in 1st activity. can me out.

secondactivity.java

add.setonclicklistener(new view.onclicklistener() {           public void onclick(view v) {             checkedcontactlist = adapter.getselecteditemarraylist();         }             intent returnintent = new intent(v.getcontext(),mainactivity.class);              returnintent.putparcelablearraylistextra("result", checkedcontactlist);             startactivity(returnintent);         }     }); 

in mainactivity.java

private arraylist<selectedlistmodel> selectedarraylist = new arraylist<selectedlistmodel>(); list<map<string, string>> datalist; public void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate); datalist = new arraylist<map<string, string>>(); bundle data = getintent().getextras(); selectedarraylist = data.getparcelablearraylist("result"); iterator<arraylist<selectedlistmodel>> = selectedarraylist.iterator();         while (it.hasnext()){selectedlistmodel selectedmodel = (selectedlistmodel)it.next(); selectedlistmodel selectedmodel = (selectedlistmodel)it1.next();             string name1 = selectedmodel.getname();                 string number1 = selectedmodel.getnumber();                 map<string, string> dict = new hashmap<string, string>(2);                 dict.put("name", name1);                 dict.put("number", number1);                 datalist.add(dict);                 //listdata.add(datalist);              }  simpleadapter adpt = new simpleadapter(this, datalist, android.r.layout.two_line_list_item, new string[] {"name", "number"}, new int[] {android.r.id.text1, android.r.id.text2});     selectedlist.setadapter(adpt); } 

you can use startactivityforresult() api document

call in activity 1

startactivityforresult( activity2, activity2requestcode) 

in activity 2

int result = "some message here"; output.putextra(name , result); setresult(result_ok, output); finish(); 

in activity 1 return value

onactivityresult (int requestcode, int resultcode, intent data)  if (requestcode == activitytworequestcode && resultcode == result_ok && data != null) num1 = data.getintextra(number1code); num2 = data.getintextra(number2code);