二維碼/條形碼工作框圖：

   輸入設備 <————> 會話 <————> 輸出設備      

設置掃描區域

• 特別要注意的是輸出設備的屬性：rectOfInterest的坐標系是橫屏坐標系，因此要進行轉換

1. 懶加載

    //1,輸入設備
    private lazy var inputDevice:AVCaptureDeviceInput? = {
        let device = AVCaptureDevice.defaultDeviceWithMediaType(AVMediaTypeVideo)
        return try! AVCaptureDeviceInput.init(device: device)
    }()
    //2,會話
    private lazy var session:AVCaptureSession? = {
         return AVCaptureSession.init()
    }()
    //3，輸出設備，設置輸出對象解析數據時聚焦的區域，默認值是全屏幕，也就是屏幕哪里掃到了二維碼就聚焦哪， CGRect(x: 0, y: 0, width: 1, height: 1)，現在要求只聚焦制定框內的二維碼
    private lazy var outputDevice:AVCaptureMetadataOutput? = {
       let output = AVCaptureMetadataOutput()
        // 通過對這個值的觀察, 我們發現傳入的是比例
        // 注意: 參照是以橫屏的左上角作為, 而不是以豎屏
        // 1.獲取屏幕的frame
        let viewRect = self.view.frame
        // 2.獲取掃描容器的frame
        let containerRect = self.customContainerView.frame
        let x = containerRect.origin.y / viewRect.height;
        let y = containerRect.origin.x / viewRect.width;
        let width = containerRect.height / viewRect.height;
        let height = containerRect.width / viewRect.width;
        
         output.rectOfInterest = CGRect(x: x, y: y, width: width, height: height)
        
        return output
    }()
    //4,預覽掃描
    private lazy var previewLayer:AVCaptureVideoPreviewLayer = {
        return AVCaptureVideoPreviewLayer.init(session: self.session)
    }()

    //5，聚焦框
    private lazy var focusLayer:CALayer = {
        var va = CALayer.init()
        return va
    }()

2.開始掃描

//二維碼掃描
    func QRScanning() -> Void {
        
        //1,確認session是否可以添加輸入設備
        if !(session?.canAddInput(inputDevice))!{
            return
        }
        //2,確認session是否可以添加輸出設備
        if !(session?.canAddOutput(outputDevice))! {
            return
        }
        //3,添加輸入輸出設備
        session?.addInput(inputDevice)
        session?.addOutput(outputDevice)
        
        //4,設置輸出設備能夠解析的數據
        outputDevice?.metadataObjectTypes = outputDevice?.availableMetadataObjectTypes
    
        //5，設置監聽輸出解析到的數據，調用代理方法
        outputDevice?.setMetadataObjectsDelegate(self, queue:dispatch_get_main_queue())
        
        //6,添加預覽圖層,使得預覽曾掃描框在一個限定范圍內
        previewLayer.frame = view.frame
        view.layer.insertSublayer(previewLayer, atIndex: 0)
        
        //7，添加自定義的聚焦框
        focusLayer.frame = view.bounds
        view.layer.addSublayer(focusLayer)

        //8,開始掃描
        session?.startRunning()
    }

3.實現代理方法

extension QRBarCodeViewController:AVCaptureMetadataOutputObjectsDelegate{
    func captureOutput(captureOutput: AVCaptureOutput!, didOutputMetadataObjects metadataObjects: [AnyObject]!, fromConnection connection: AVCaptureConnection!)
    {
        //metadataObjects元素類型是AVMetadataObject
        guard let metadata: AVMetadataObject? = metadataObjects.last as? AVMetadataObject else{
            return
        }

        //通過預覽圖層將數據，轉換為能識別的數據類型
        let canReadData = previewLayer.transformedMetadataObjectForMetadataObject(metadata)
        
        // DyLog(metadata)  before:corners:{ 0.5,0.6 0.6,0.6 0.6,0.3 0.5,0.3 },
        //DyLog(canReadData as! AVMetadataMachineReadableCodeObject)
        //after convert:corners:{ 162.5,309.2 166.7,401.7 260.1,401.6 258.7,307.2 },
        
        //清除之前的圖層
        clearLayer()
        guard let pointArrMetaData = canReadData as? AVMetadataMachineReadableCodeObject else{
            return
        }
        //畫框
        drawLine(pointArrMetaData)
        

    }
    
    
    func drawLine(data:AVMetadataMachineReadableCodeObject!) -> Void {
        

        //校驗數據,查看數據的數組中是否含有corners，沒有直接返回，否則會數組越界
        guard let array = data!.corners else{
            return
        }
        
        //1,創建會話圖層,畫貝塞爾曲線的圖層CAShapeLayer
        let drawLayer = CAShapeLayer.init()
        //設置邊框寬度和顏色
        drawLayer.fillColor = UIColor.clearColor().CGColor
        drawLayer.strokeColor = UIColor.greenColor().CGColor
        drawLayer.lineWidth = 3
        
        //2，創建貝塞爾曲線
        let bezierPath = UIBezierPath.init()
        var index = 0;
        //將數組中的字典轉為CGPoint
        var start = CGPointZero
        CGPointMakeWithDictionaryRepresentation((array[index] as! CFDictionary), &start)
        
        bezierPath.moveToPoint(start)
        
        //3，畫框
        while index < array.count-1 {
            index += 1
            DyLog(index)
            CGPointMakeWithDictionaryRepresentation((array[index] as! CFDictionary),&start)
            bezierPath.addLineToPoint(start)
        }
        //4，關閉路徑
        bezierPath.closePath()
        
        //5,將貝塞爾曲線添加到圖層上
        drawLayer.path = bezierPath.CGPath
        
        //6,將圖層添加到聚焦界面上
        focusLayer.addSublayer(drawLayer)
    }
    
    func clearLayer() -> Void {
        guard let sublayers = focusLayer.sublayers else{
            return
        }
        for layer in sublayers {
            layer.removeFromSuperlayer()
        }
    }
}