java - How to invalidate ListView for new data when using ListAdapter -

i making use of default listview in fragment show data being called url. there swiperefreshlayout listview contained. when refresh, old data still in listview , new data added @ top of list. there way invalidate old data?
have made use of listadapter created simpleadapter class so:
listadapter adapter = new simpleadapter(getactivity(), newsitemlist, r.layout.list_item, new string[]{tag_title, tag_date, tag_owner}, new int[]{r.id.news_title, r.id.news_date, r.id.news_owner}); lvgeneralnews.setadapter(adapter);

i have tried make adapter null or use invalidate() method comes listview. adapter not have notifydatasetchanged() method.
the newsitemlist arraylist has data url. declared so:
arraylist<hashmap<string,string>> newsitemlist;

the important : clear arraylist> newsitemlist when new data? if u repeat:

      listadapter adapter = new simpleadapter(getactivity(), newsitemlist, r.layout.list_item, new string[]{tag_title, tag_date, tag_owner}, new int[]{r.id.news_title, r.id.news_date, r.id.news_owner});         lvgeneralnews.setadapter(adapter);