swift扫描二维码

扫描二维码可是说是很常见的需求了，利用相机扫描出二维码中的URL。主要用到的是AVFoundation框架。
首先要获取手机的相机权限，在info.plist文件中添加两个键值对Privacy - Photo Library Usage Description与Privacy - Camera Usage Description
代码部分:

        let alertAction = UIAlertController.init(title: "需要获取相机权限", message: nil, preferredStyle: .actionSheet)
        alertAction.addAction(UIAlertAction.init(title: "获取相机权限", style: .default, handler: { (alertCamera) in
            
            let picker:UIImagePickerController = UIImagePickerController()
            picker.delegate = self
            picker.sourceType = .camera
            picker.allowsEditing = true
            self.present(picker, animated: true, completion: nil)
        }))

接着需要做一个扫描框:

扫描框

    var lineImageView: UIImageView!
    var lineImage: UIImage!
    var overlayView: UIView!
    var ratioView: UIView!

    func createView() {
        lineImage = UIImage.init(named: "scanqrcode_line")
        lineImageView = UIImageView.init(image: lineImage)
        lineImageView.frame = CGRect(x: (UIScreen.main.bounds.size.width - 240) * 0.5, y:100 - self.lineImage.size.height * 0.5, width: 240, height: self.lineImage.size.height)
        self.view.addSubview(lineImageView)
        self.lineImageView.layer.zPosition = 2
        
        self.overlayView = UIView.init(frame: CGRect(x: 0 , y: 0 ,width: self.view.frame.size.width, height: self.view.frame.size.height))
        self.overlayView.alpha = 0.5
        self.overlayView.backgroundColor = UIColor.black
        self.view.addSubview(self.overlayView)
        self.overlayView.layer.zPosition = 2
        
        self.ratioView = UIView.init(frame: CGRect(x: (UIScreen.main.bounds.size.width - 240) * 0.5 , y: 100 ,width: 240, height: 240))
        self.ratioView.layer.borderColor = UIColor.lightGray.cgColor
        self.ratioView.layer.borderWidth = 1
        self.view.addSubview(self.ratioView)
        self.ratioView.layer.zPosition = 2
        
        let maskLayer: CAShapeLayer! = CAShapeLayer.init()
        let path: CGMutablePath! = CGMutablePath()
        // left
        path.addRect(CGRect(x:0,y:0,width:self.ratioView.frame.origin.x,height:self.overlayView.frame.size.height))
        // right
        path.addRect(CGRect(x:self.ratioView.frame.origin.x + self.ratioView.frame.size.width,y:0,width:self.overlayView.frame.size.width - self.ratioView.frame.origin.x - self.ratioView.frame.size.width,height:self.overlayView.frame.size.height))
        // top
        path.addRect(CGRect(x:0,y:0,width:self.overlayView.frame.size.width,height:self.ratioView.frame.origin.y))
        // bottom
        path.addRect(CGRect(x:0,y:self.ratioView.frame.origin.y + self.ratioView.frame.size.height,width:self.overlayView.frame.size.width,height:self.overlayView.frame.size.height - self.ratioView.frame.origin.y + self.ratioView.frame.size.height))
        
        maskLayer.path = path
        self.overlayView.layer.mask = maskLayer
        
        let cornerImg = UIImage.init(named: "scanqrcode_corner")
        
        let cornerImgView = UIImageView.init(image: UIImage.init(named: "scanqrcode_corner"))
        cornerImgView.frame = CGRect(x:(UIScreen.main.bounds.size.width - 240) * 0.5, y:100,width: (cornerImgView.image?.size.width)!,height:(cornerImgView.image?.size.height)!)
        self.view.addSubview(cornerImgView)
        cornerImgView.layer.zPosition = 2
        
        let ratateImg = UIImage.init(cgImage: (cornerImg?.cgImage)!, scale: 1, orientation: UIImageOrientation.right)
        let ratateImgView = UIImageView.init(image: ratateImg)
        ratateImgView.frame = CGRect(x:(UIScreen.main.bounds.size.width - 240) * 0.5 + 240 - (cornerImg?.size.width)!, y:100 , width: (cornerImg?.size.width)!, height: (cornerImg?.size.height)!)
        self.view.addSubview(ratateImgView)
        ratateImgView.layer.zPosition = 2
        self.downAnimate()
    }
    func downAnimate() {
        UIView.animate(withDuration: 3, animations: { 
            self.lineImageView.frame = CGRect(x: (UIScreen.main.bounds.size.width - 240) * 0.5, y:340 - self.lineImage.size.height * 0.5,width: 240,height: self.lineImageView.frame.size.height)
        }) { (finished) in
            self.upAnimate()
        }
    }
    
    func upAnimate() {
        UIView.animate(withDuration: 3, animations: {
            self.lineImageView.frame = CGRect(x: (UIScreen.main.bounds.size.width - 240) * 0.5, y:100 - self.lineImage.size.height * 0.5,width: 240,height: self.lineImageView.frame.size.height)
        }) { (finished) in
            self.downAnimate()
        }
    }

接下来是重头戏部分，二维码扫描:

    // AVCaptureSession是AVFoundation的核心类,用于捕捉视频和音频,协调视频和音频的输入和输出流
    var session: AVCaptureSession!
    // 视频预览层
    var preview: AVCaptureVideoPreviewLayer!

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        self.startReading()
    }
    
    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        self.stopReading()
    }

    func startReading() {
        // 获取 AVCaptureDevice 实例
        let device: AVCaptureDevice = AVCaptureDevice.defaultDevice(withMediaType: AVMediaTypeVideo)
        
        do {
            // 初始化输入流
            let input = try AVCaptureDeviceInput.init(device: device)
            
            // 初始化session
            self.session = AVCaptureSession()
            self.session.sessionPreset = AVCaptureSessionPresetHigh
            
            // 添加输入设备到会话对象
            self.session.addInput(input)
            
            // 初始化输出流
            let output: AVCaptureMetadataOutput = AVCaptureMetadataOutput.init()
            self.session.addOutput(output)
            output.setMetadataObjectsDelegate(self, queue: DispatchQueue.main)
            
            // 条码类型
            output.metadataObjectTypes = [AVMetadataObjectTypeQRCode]
            
            // 创建输出对象
            self.preview = AVCaptureVideoPreviewLayer.init(session: session)
            self.preview.videoGravity = AVLayerVideoGravityResizeAspectFill
            self.preview.frame = CGRect(x:0,y:0,width:self.view.frame.size.width,height:self.view.frame.size.height)
            self.view.layer.addSublayer(self.preview)
            
            // 开始会话
            self.session.startRunning()
            
        }catch{
            print(error)
            return
        }
        
    }
    
    func stopReading() {
        self.session.startRunning()
        self.session = nil
    }

需要遵循AVCaptureMetadataOutputObjectsDelegate协议,扫描结果要从代理方法中获得:

    //当AVCaptureMetadataOutput对象识别QR code将触发该方法 
    func captureOutput(_ captureOutput: AVCaptureOutput!, didOutputMetadataObjects metadataObjects: [Any]!, from connection: AVCaptureConnection!) {
        // 确认是否元数据对象数组是否不为nil并至少包含一个对象,如果为nil,显示对应提示信息
        if metadataObjects == nil || metadataObjects.count == 0 {
            resultLabel.text = "二维码错误"
        }
        
        // 获取元数据
        let metadataObj = metadataObjects[0] as! AVMetadataMachineReadableCodeObject
        
        if metadataObj.type == AVMetadataObjectTypeQRCode {
            print(metadataObj.stringValue)
            let alertAction = UIAlertController.init(title: "\(metadataObj.stringValue!)", message: nil, preferredStyle: .alert)
            self.present(alertAction, animated: true, completion: nil)
            
        }
    }

扫描结果

其中遇到一个问题，扫描中会出现崩溃，最终是因为添加输出流output需要在setMetadataObjectsDelegate之前进行,解决这个之后完美运行:

self.session.addOutput(output)
output.setMetadataObjectsDelegate(self, queue: DispatchQueue.main)