Apps Adding a item from another activity to ExpandableListView

[GerritHoekstra]

I want to add a item to the child Today from another activity to the ExpandableListView. The activity where I want to add it is named LocHistory, here is a the code to add something to the list:

[HIGH] static void addListData(final Context context) {
List<NewsItem> list = listDataChild.get("Today");
NewsItem newsData = new NewsItem();
newsData = new NewsItem();
newsData.setHeadline("11.11111, 1.1111");
newsData.setSpeed("1.11KM/H");
newsData.setDirection("111");
newsData.setDate("11-1-1111 11:11:11");
list.add(0, newsData);
listDataChild.put("Today", list);
}[/HIGH]

This is working when I have call the function in the same class (LocHistory). But when I call it in MainActivity like this:

[HIGH] public class MainActivity extends Activity {

Button button2;

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

button2 = (Button) this.findViewById(R.id.button2);

button2.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
LocHistory.addListData(getBaseContext());
}
});
}
}[/HIGH]

Then there is nothing added to the list. Is it possible to add a item from another activity to ExpandableListView? I want if there's something added that the class LocHistory is not going to open, so I think startActivity with a intent is not a option here (but i'm not sure).

(The java sources can be found here:
MainActivity.java pastebin.com/YWyfznwv
LocHistory.java - pastebin.com/XJ274C61
NewsItem.java - pastebin.com/uhmXbnhJ
ExpandableListAdapter.java - pastebin.com/5jPV8daz)