Have the current expanded group position stored in a variable. In onGroupExpanded do the following.
private int lastExpandedPosition = -1;
private ExpandableListView lv; //your expandable listview
...
lv.setOnGroupExpandListener(new OnGroupExpandListener() {
@Override
public void onGroupExpand(int groupPosition) {
if (lastExpandedPosition != -1
&& groupPosition != lastExpandedPosition) {
lv.collapseGroup(lastExpandedPosition);
}
lastExpandedPosition = groupPosition;
}
});