iOS
QR-codescanner

Invoering

UIViewController scannen voor QR en video-invoer weergeven

import AVFoundation
class QRScannerViewController: UIViewController,
     AVCaptureMetadataOutputObjectsDelegate {
   
    func viewDidLoad() {
        self.initCaptureSession()
    }
    
    private func initCaptureSession() {
        let captureDevice = AVCaptureDevice
            .defaultDevice(withMediaType: AVMediaTypeVideo)
        do {
            let input = try AVCaptureDeviceInput(device: captureDevice)
            let captureMetadataOutput = AVCaptureMetadataOutput()
            self.captureSession?.addOutput(captureMetadataOutput)
            captureMetadataOutput.setMetadataObjectsDelegate(self,
                 queue: DispatchQueue.main)
            captureMetadataOutput
                .metadataObjectTypes = [AVMetadataObjectTypeQRCode]
            
            self.videoPreviewLayer = 
                AVCaptureVideoPreviewLayer(session: self.captureSession)
            self.videoPreviewLayer?
                .videoGravity = AVLayerVideoGravityResizeAspectFill
            self.videoPreviewLayer?.frame =    
                self.view.layer.bounds

            self._viewController?.view.layer
                .addSublayer(videoPreviewLayer!)
            self.captureSession?.startRunning()
        } catch {
            //TODO: handle input open error
        }
    }
    private func dismissCaptureSession() {
        if let running = self.captureSession?.isRunning, running {
            self.captureSession?.stopRunning()
        }
        self.captureSession = nil
        self.videoPreviewLayer?.removeFromSuperLayer()
        self.videoPreviewLayer = nil
    }
    
    func captureOutput(_ captureOutput: AVCaptureOutput, 
        didOutputMetadataObjects metadataObjects: [Any]!, 
        from connection: AVCaptureConnection) {
        guard metadataObjects != nil && metadataObjects.count != 0 else {
            //Nothing captured
            return
        }

        if let metadataObj = 
            metadataObjects[0] as? AVMetadataMachineReadableCodeObject {
            guard metadataObj.type == AVMetadataObjectTypeQRCode else {
                return
            }

            let barCodeObject = videoPreviewLayer?
                .transformedMetadataObject(for: 
                    metadataObj as AVMetadataMachineReadableCodeObject)
                 as! AVMetadataMachineReadableCodeObject
        
            if let qrValue = metadataObj.stringValue {
                self.handleQRRead(value: qrValue)
            }
        }
    }

    private handleQRRead(value: String) {
        //TODO: Handle the read qr
    }
    private captureSession: AVCaptureSession?
    private videoPreviewLayer: AVCaptureVideo
}

handleQRRead - wordt aangeroepen bij een geslaagde scan initCaptureSession - initialiseer het scannen voor QR en camera-invoer en dismissCaptureSession - verberg de camera-invoer en stop met scannen

QR-code scannen met AVFoudation-framework

Voorafgaand aan iOS 7, wanneer u een QR-code wilt scannen, moeten we mogelijk vertrouwen op frameworks van derden of bibliotheken zoals zBar of zXing . Maar Apple introduceerde AVCaptureMetaDataOutput van iOS 7 voor het lezen van barcodes.

Om QR-code te lezen met behulp van AVFoundation , moeten we AVFoundation instellen en maken en AVCaptureSession gebruiken captureOutput:didOutputMetadataObjects:fromConnection: delegate-methode.

Stap 1

Importeer AVFoundation framework en bevestig met AVCaptureMetadataOutputObjectsDelegate protocol

import AVFoundation
class ViewController: UIViewController, AVCaptureMetadataOutputObjectsDelegate

Stap 2

QR-codelezing is volledig gebaseerd op video-opname. Maak dus een AVCaptureSession en stel apparaatinvoer en -uitvoer in om continue video vast te leggen. Voeg de onderstaande code toe in de viewDidLoad methode van de viewDidLoad

// Create an instance of the AVCaptureDevice and provide the video as the media type parameter.
let captureDevice = AVCaptureDevice.defaultDevice(withMediaType: AVMediaTypeVideo)
 
do {
    // Create an instance of the AVCaptureDeviceInput class using the device object and intialise capture session
    let input = try AVCaptureDeviceInput(device: captureDevice)
    captureSession = AVCaptureSession()
    captureSession?.addInput(input)
    
    // Create a instance of AVCaptureMetadataOutput object and set it as the output device the capture session.
    let captureMetadataOutput = AVCaptureMetadataOutput()
    captureSession?.addOutput(captureMetadataOutput)
    // Set delegate with a default dispatch queue
    captureMetadataOutput.setMetadataObjectsDelegate(self, queue: DispatchQueue.main)
    //set meta data object type as QR code, here we can add more then one type as well 
    captureMetadataOutput.metadataObjectTypes = [AVMetadataObjectTypeQRCode]


    // Initialize the video preview layer and add it as a sublayer to the viewcontroller view's layer.
    videoPreviewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
    videoPreviewLayer?.videoGravity = AVLayerVideoGravityResizeAspectFill
    videoPreviewLayer?.frame = view.layer.bounds
    view.layer.addSublayer(videoPreviewLayer!)

    // Start capture session.
    captureSession?.startRunning()
} catch {
    // If any error occurs, let the user know. For the example purpose just print out the error
    print(error)
    return
}

Stap 3

Implementeer AVCaptureMetadataOutputObjectsDelegate methode om de QR-code te lezen

func captureOutput(_ captureOutput: AVCaptureOutput!, didOutputMetadataObjects metadataObjects: [Any]!, from connection: AVCaptureConnection!) {
    
    // Check if the metadataObjects array contains at least one object. If not no QR code is in our video capture
    if metadataObjects == nil || metadataObjects.count == 0 {
        // NO QR code is being detected.
        return
    }
    
    // Get the metadata object and cast it to `AVMetadataMachineReadableCodeObject`
    let metadataObj = metadataObjects[0] as! AVMetadataMachineReadableCodeObject
    
    if metadataObj.type == AVMetadataObjectTypeQRCode {
        // If the found metadata is equal to the QR code metadata then get the string value from meta data
        let barCodeObject = videoPreviewLayer?.transformedMetadataObject(for: metadataObj)
        
        if metadataObj.stringValue != nil {
           // metadataObj.stringValue is our QR code
        }
    }
} 

hier kunnen metadata-objecten u ook de grenzen van de QR-code op de camerafeed geven. Om de grenzen te krijgen, geeft u het metadata-object eenvoudig door aan de transformedMetadataObject methode van videoPreviewLayer zoals hieronder.

let barCodeObject = videoPreviewLayer?.transformedMetadataObject(for: metadataObj)
        qrCodeFrameView?.frame = barCodeObject!.bounds