void onGroupTreeChanged(GroupTreeChangedEvent event)
groupingoperation completes, whether it started as a direct call to
regroup()or data changing, including incremental changes.
changeType is "groupBy",
ListGrid.groupBy() should have been called at the beginning of the operation, and
ListGrid.groupByComplete() will be called
immediately before this method. If
changeType is "regroup", then
ListGrid.regroup() should have been called at the beginning
of the operation.
event- the event