public void callback( final String[] operators ) {
CEPOperatorsDropdown dropdown = new CEPOperatorsDropdown( operators,
constraint );
callback.callback( dropdown );
dropdown.addValueChangeHandler( new ValueChangeHandler<OperatorSelection>() {
public void onValueChange( ValueChangeEvent<OperatorSelection> event ) {
onDropDownValueChanged( event, constraint, inner, row, col );
}
} );