在视频程序的编写过程中，我们经常要使用摄像头，在使用摄像头前有必要对摄像头的现有状态做个检测:

1.被占用

2.没安装摄像头

3.正常

看下面代码：

<?xml version="1.0" encoding="utf-8"?>
<mx:WindowedApplication xmlns:mx="http://www.adobe.com/2006/mxml"
    layout="absolute" creationComplete="init()">

    <mx:Script>
        <![CDATA[

            import mx.controls.Alert;
            private var camera:Camera;
            private var isExistsCamera:Boolean=false;
            private var isBusyCamera:Boolean=false;
            private var intervalId:uint;
            private var times:int;

            private function init():void
            {
                camera=Camera.getCamera();
               if (camera == null)
                {
                   if (Camera.names.length <= 0)
                    {
                        this.isExistsCamera=false;
                        Alert.show("没安装摄像头");
                    }
                }
                else
                {
                    this.vdpaly.attachCamera(this.camera);
                    this.isCameraBusy();
                }
            }

            private function isCameraBusy():void
            {
                this.intervalId=setInterval(callback,50);
            }

            private function callback():void
            {
                trace("currentFPS=" + camera.currentFPS.toString());

               if (camera.currentFPS > 0)
                {
                    //视频设备可用
                    clearInterval(this.intervalId);
                    this.isBusyCamera=false;
                    Alert.show("摄像头正常");
                }
                else
                {
                    times++;
                    trace("times=" + times.toString());

                    if (times > 30)
                    {
                        //视频设备忙
                        clearInterval(intervalId);
                        this.isBusyCamera=true;
                        Alert.show("摄像头被占用");
                    }
                }
            }

             private function cl():void
            {
                Alert.show(this.camera.currentFPS.toString());
            }

        ]]>
    </mx:Script>

    <mx:VideoDisplay   id="vdpaly"  click="cl()" x="44" y="64" width="232" height="236"/>

</mx:WindowedApplication>

代码说明：

camera == null，那么就是没安装摄像头

如果摄像头被占用，那么camera.currentFPS 肯定不会大 于0,而是等于0

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