Flex中如何利用firstVisibleItem属性，设置或取得第一个显示节点

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:Script>
8. <![CDATA[
9. import mx.events.FlexEvent;
10. import mx.events.ListEvent;
12. private function tree_creationComplete(evt:FlexEvent):void {
13. tree.expandChildrenOf(xmlDP, true);
14. }
16. private function comboBox_change(evt:ListEvent):void {
17. tree.firstVisibleItem = comboBox.selectedItem;
18. }
19. ]]>
20. </mx:Script>
22. <mx:XMLid="xmlDP">
23. <node>
24. <nodelabel="1.a" />
25. <nodelabel="1.b" />
26. <nodelabel="1.c">
27. <nodelabel="1.c.i" />
28. <nodelabel="1.c.ii" />
29. <nodelabel="1.c.iii" />
30. <nodelabel="1.c.iv" />
31. <nodelabel="1.c.v" />
32. </node>
33. <nodelabel="1.d" />
34. <nodelabel="1.e">
35. <nodelabel="1.e.i" />
36. <nodelabel="1.e.ii" />
37. <nodelabel="1.e.iii">
38. <nodelabel="1.e.iii.A" />
39. </node>
40. <nodelabel="1.e.iv" />
41. </node>
42. <nodelabel="1.f" />
43. </node>
44. </mx:XML>
46. <mx:ApplicationControlBardock="true">
47. <mx:FormstyleName="plain">
48. <mx:FormItemlabel="firstVisibleItem:">
49. <mx:ComboBoxid="comboBox"
50. dataProvider="{xmlDP..node}"
51. labelField="@label"
52. change="comboBox_change(event);"/>
53. </mx:FormItem>
54. </mx:Form>
55. </mx:ApplicationControlBar>
57. <mx:Treeid="tree"
58. dataProvider="{xmlDP}"
59. labelField="@label"
60. showRoot="false"
61. alternatingItemColors="[#EEEEEE, #FFFFFF]"
62. width="50%"
63. rowCount="6"
64. creationComplete="tree_creationComplete(event);"/>
66. </mx:Application>