Flex中如何将Tree作为PopUpButton的弹出菜单

main.mxml

1. <?xml version="1.0" encoding="utf-8"?>
2. <mx:Applicationxmlns:mx="http://www.adobe.com/2006/mxml"
3. layout="vertical"
4. verticalAlign="middle"
5. backgroundColor="white">
7. <mx:Style>
8. Tree {
9. textAlign: left;
10. fontWeight: normal;
11. }
12. </mx:Style>
14. <mx:XMLid="mlb" source="mlb.xml" />
16. <mx:ApplicationControlBardock="true">
17. <mx:PopUpButtonlabel="Please select a team...">
18. <mx:popUp>
19. <mx:Treeid="tree"
20. dataProvider="{mlb}"
21. labelField="@label"
22. showRoot="false"
23. width="200"
24. rowCount="8"/>
25. </mx:popUp>
26. </mx:PopUpButton>
27. </mx:ApplicationControlBar>
29. </mx:Application>