//MARK: 初始化二维码扫描器
    func initQRCodeScaner(){
        // 获取 AVCaptureDevice 实例
        _captureDevice = AVCaptureDevice.defaultDeviceWithMediaType(AVMediaTypeVideo)
        // 初始化输入流
        do{
            try _inputStream = AVCaptureDeviceInput(device: _captureDevice!)
        }catch{
            print("初始化输入流 with device 失败")
        }
        if _inputStream == nil{
            return
        }
        _ctr._isScaning = true
        // 创建会话
        _captureSession = AVCaptureSession()
        _captureSession?.addInput(_inputStream)
        // 初始化输出流
        _captureMetadataOutput = AVCaptureMetadataOutput()
        //设置区域
        //CGRectMake（y的起点/屏幕的高，x的起点/屏幕的宽，扫描的区域的高/屏幕的高，扫描的区域的宽/屏幕的宽）
        _captureMetadataOutput?.rectOfInterest = CGRect(x: _scanRect!.origin.y/kScreenHeight, y: _scanRect!.origin.x/kScreenWidth, width: _scanRect!.height / kScreenHeight, height: _scanRect!.width / kScreenWidth)
        // 添加输出流
        _captureSession?.addOutput(_captureMetadataOutput)
        // 创建dispatch queue.
        let dispatchQueue = dispatch_queue_create(kScanQRCodeQueueName, nil)
        _captureMetadataOutput?.setMetadataObjectsDelegate(self, queue: dispatchQueue)
        // 设置元数据类型 AVMetadataObjectTypeQRCode
        let objArray = NSArray(objects: AVMetadataObjectTypeQRCode)
        _captureMetadataOutput?.metadataObjectTypes = objArray as [AnyObject]
        // 创建输出对象
        _videoPreviewLayer = AVCaptureVideoPreviewLayer(session: _captureSession)
        _videoPreviewLayer?.videoGravity = AVLayerVideoGravityResizeAspectFill
        _videoPreviewLayer?.frame = self.view.bounds
        self.view.layer.insertSublayer(_videoPreviewLayer!, atIndex: 0)

    }