Flex 根据DataGridColumn 的值动态显示相对应的图片

如果从后台获取的公文ID为空，那么显示的图片是灰色的。如果不为空，带颜色的图标。

<mx:DataGridColumn dataField="doc" editable="false" headerText="公文">
							<mx:itemRenderer>
								<fx:Component>
									<mx:VBox horizontalScrollPolicy="off" verticalScrollPolicy="off">
										<fx:Script>
											<![CDATA[
												import mx.events.FlexEvent;
												import mx.controls.Alert;
												protected function xqDocImg_initializeHandler(event:FlexEvent):void
												{
													// TODO Auto-generated method stub
													if(data==""||data==null){
														docImg.source="assets/pdf/22.png";
													}else{
														docImg.source="assets/pdf/21.png";
													}
												}
												
												protected function docImg_clickHandler(event:MouseEvent):void
												{
													// TODO Auto-generated method stub
													if(data==""||data==null){
														Alert.show("没有公文，无法查看");
													}else{
														
													}
												}
												
											]]>
										</fx:Script>
										<s:Image id="docImg" initialize="xqDocImg_initializeHandler(event)" click="docImg_clickHandler(event)"></s:Image>
									</mx:VBox>
								</fx:Component>
							</mx:itemRenderer>
						</mx:DataGridColumn>