In this codes ,I recent can catch the camera, but now I can't. why?
<?xml version="1.0" encoding="utf-8"?>
<f:Screen xmlns:fx="http://ns.adobe.com/mxml/2009"
		  xmlns:f="library://ns.feathersui.com/mxml"
		  removedFromStage="panelscreen1_removedFromStageHandler(event)"
		  transitionInComplete="panelscreen1_transitionInCompleteHandler(event)">
	<fx:Script>
		<![CDATA[
			import flash.events.PermissionEvent;
			import flash.permissions.PermissionStatus;
			
			import feathers.core.PopUpManager;
			import feathers.layout.HorizontalLayoutData;
			import feathers.layout.VerticalLayoutData;
			
			import starling.display.Image;
			import starling.events.Event;
			import starling.textures.Texture;
			private var cam:Camera;
			protected function back_triggeredHandler(event:starling.events.Event):void
			{
				// TODO Auto-generated method stub
				this.dispatchEventWith(Event.COMPLETE);
			}
			protected function initCamera():void{
					
				
				if(Camera.permissionStatus==PermissionStatus.GRANTED||Camera.permissionStatus==PermissionStatus.ONLY_WHEN_IN_USE){
				
					cam.setMode(320,320,24,false);
					cam.setQuality(0,0);
					
					var texture:Texture=Texture.fromCamera(cam,1,function():void{					
						
						var image:Image= new Image(texture);
						image.width=320;
						image.height=320;
						qrView.addChild(image);						
					});
				}else{							
					cam.addEventListener( PermissionEvent.PERMISSION_STATUS,permissionHandler);
					cam.requestPermission();				
				}
			}
			
			protected function panelscreen1_transitionInCompleteHandler(event:starling.events.Event):void
			{
				cam=new Camera;		
				cam=Camera.getCamera();
				initCamera();				
			}
			
			
			protected function permissionHandler(event:*):void{
				switch(event.status){
					case PermissionStatus.GRANTED:
						initCamera();
						break;
					case PermissionStatus.ONLY_WHEN_IN_USE:
						initCamera();
						break;
					case PermissionStatus.DENIED:
						PopUpManager.removeAllPopUps();
						break;
				}
			}
			
			protected function panelscreen1_removedFromStageHandler(event:starling.events.Event):void
			{

			}
		]]>
	</fx:Script>
	<f:layout>
		<f:VerticalLayout/>
	</f:layout>
	<f:Header id="hd" title="二维码扫一扫">
		<f:leftItems>
			<fx:Vector type="starling.display.DisplayObject">
				<f:Button id="back" label="返回" layoutData="{new HorizontalLayoutData(NaN,100)}"/>
			</fx:Vector>			
		</f:leftItems>
	</f:Header>	
	<f:LayoutGroup layoutData="{new VerticalLayoutData(100,100)}">	
		<f:layout>
			<f:AnchorLayout/>
		</f:layout>
		<f:LayoutGroup id="qrView" />
	</f:LayoutGroup>
	<f:TextInput id="info" isEditable="false" layoutData="{new VerticalLayoutData(100,100)}"
				 text="请将二维码置于扫描框内。">
		
	</f:TextInput>
</f:Screen>