Need refresh the chat contents freshly topic

how to refresh the chat tab after entering the messasge and click the button. for now it loads the chat contents multiple times and listings. i need to clear and load fresh contents in each interval.

here i used to refresh the activity

private Runnable runnable = new Runnable() {
@override
public void run() {

new LoadOutboxRefresh().execute();

handler.postDelayed(this, 100);
}
};

LoadOutboxRefresh class have the list of chat contents. it loads the interval time but showing multiple contents as same list.

please anyone help me to resolve this....