It seems the AdvancedDataGrid creation sequence in flex 4 is different from it is in flex 3. For example, in a mxml file, I have an AdvancedDataGrid component and override initializationComplete() method. In this method, I'll do some initialization with the reference of AdvancedDataGrid, but I get null reference exception. Why can't I get AdvancedDataGrid reference in initializationComplete method? Does that mean the AdvancedDataGrid isn't created yet? How can I gurantee it is created before I use the reference? Thanks.