Flex AdvancedDataGrid的使用，谁能告诉我呀？

注：第一列是带Checkbox的Tree。
还有问题请教各位：
   labelField是元素对象的属性是显示不了（carInfo.car_name），好像只可显示同级的属性怎么解决？希望各位能帮助我，Thanks!
 <mx:AdvancedDataGrid id="adg"  width="100%" height="100%" dataProvider="{instance.cars}"
        variableRowHeight="true"  wordWrap="true" verticalGridLineColor="0x339900" headerColors="[0x339900,0xFFEBCD]" horizontalGridLineColor="0x8B4513">
          <mx:columns>
      <mx:AdvancedDataGridColumn headerText="vehicle name" dataField="carInfo.car_name"/>
      <mx:AdvancedDataGridColumn headerText="terminal key" dataField="carInfo.terminal_key" />
      <mx:AdvancedDataGridColumn headerText="sim code" dataField="carInfo.sim_code"/>
            </mx:columns>
  </mx:AdvancedDataGrid>
/*****vo.Car****/
[Bindable]
public class Car
 {
  private var _term:BaseTerminal;
  private var _imageName:String;
  private var _icon:Icon;
  private var _carInfo:CarInfo;
   ...............
}
[Bindable]
 [RemoteClass(alias="vo.Car")]
 public class CarInfo
 {
  public var car_name:String;
  public var car_id:String;
  public var group_name:String;
  public var speed:int;
  public var terminal_key:String;
  public var sim_code:String;
  public var fuel_min:int;
  public var fuel_max:int;
  public var fuel_size:int;
...........
}