Android : Android Spinner GetSelection

I work with Android Project. This is my small code

fromAdapter = new SpinAdapter(getActivity(), 0, new ArrayList<Cities>());
mFrom.setAdapter(fromAdapter);

{Async-call}.onOperationSuccess{
           fromAdapter.addAll(list);
           Object selectionId=mFrom.getSelection()
}

var selectionId is null ? why?

Can anybody help me?