QR scanner not working but not getting any errors? - ios

Question

import UIKit
import AVFoundation
class ViewController: UIViewController, AVCaptureMetadataOutputObjectsDelegate {
var video = AVCaptureVideoPreviewLayer()
#IBOutlet weak var square: UIImageView!
override func viewDidLoad() {
super.viewDidLoad()
//creates the session
let session = AVCaptureSession()
//Defines the capture device
guard let captureDevice = AVCaptureDevice.default(for: AVMediaType.video),
let input = try? AVCaptureDeviceInput(device: captureDevice) else { return }
session.addInput(input)
let output = AVCaptureMetadataOutput()
session.addOutput(output)
output.setMetadataObjectsDelegate(self, queue: DispatchQueue.main)
output.metadataObjectTypes = [AVMetadataObject.ObjectType.qr]
video = AVCaptureVideoPreviewLayer(session: session)
video.frame = view.layer.bounds
view.layer.addSublayer(video)
self.view.bringSubviewToFront(square)
session.startRunning()
}
func captureOutput(_ captureOutput: AVCaptureOutput!, didOutputMetadataObjects
metadataObjects: [Any]!, from connection: AVCaptureConnection!) {
if metadataObjects != nil && metadataObjects.count != 0 {
if let object = metadataObjects[0] as? AVMetadataMachineReadableCodeObject {
if object.type == AVMetadataObject.ObjectType.qr {
let alert = UIAlertController(title: "QR Code", message: object.stringValue,
preferredStyle: .alert)
alert.addAction(UIAlertAction(title: "Retake", style: .default,
handler: nil))
alert.addAction(UIAlertAction(title: "Copy", style: .default, handler: { (nil) in
UIPasteboard.general.string = object.stringValue
}))
present(alert, animated: true, completion: nil)
}
}
}
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
}
No errors print out and terminal is also empty. This is my updated version of some Swift 3 code that did work so don't understand why it won't work

Answer 1

Try this, working fine with me - using Swift 5.2. Modify the function found() with whatever you want with the returned string. Reference: qr scanner
import AVFoundation
import UIKit
class ScannerViewController: UIViewController, AVCaptureMetadataOutputObjectsDelegate {
var captureSession: AVCaptureSession!
var previewLayer: AVCaptureVideoPreviewLayer!
override func viewDidLoad() {
super.viewDidLoad()
view.backgroundColor = UIColor.black
captureSession = AVCaptureSession()
guard let videoCaptureDevice = AVCaptureDevice.default(for: .video) else { return }
let videoInput: AVCaptureDeviceInput
do {
videoInput = try AVCaptureDeviceInput(device: videoCaptureDevice)
} catch {
return
}
if (captureSession.canAddInput(videoInput)) {
captureSession.addInput(videoInput)
} else {
failed()
return
}
let metadataOutput = AVCaptureMetadataOutput()
if (captureSession.canAddOutput(metadataOutput)) {
captureSession.addOutput(metadataOutput)
metadataOutput.setMetadataObjectsDelegate(self, queue: DispatchQueue.main)
metadataOutput.metadataObjectTypes = [.qr]
} else {
failed()
return
}
previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
previewLayer.frame = view.layer.bounds
previewLayer.videoGravity = .resizeAspectFill
view.layer.addSublayer(previewLayer)
captureSession.startRunning()
}
func failed() {
let ac = UIAlertController(title: "Scanning not supported", message: "Your device does not support scanning a code from an item. Please use a device with a camera.", preferredStyle: .alert)
ac.addAction(UIAlertAction(title: "OK", style: .default))
present(ac, animated: true)
captureSession = nil
}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
if (captureSession?.isRunning == false) {
captureSession.startRunning()
}
}
override func viewWillDisappear(_ animated: Bool) {
super.viewWillDisappear(animated)
if (captureSession?.isRunning == true) {
captureSession.stopRunning()
}
}
func metadataOutput(_ output: AVCaptureMetadataOutput, didOutput metadataObjects: [AVMetadataObject], from connection: AVCaptureConnection) {
captureSession.stopRunning()
if let metadataObject = metadataObjects.first {
guard let readableObject = metadataObject as? AVMetadataMachineReadableCodeObject else { return }
guard let stringValue = readableObject.stringValue else { return }
AudioServicesPlaySystemSound(SystemSoundID(kSystemSoundID_Vibrate))
found(code: stringValue)
}
dismiss(animated: true)
}
func found(code: String) {
print(code)
}
override var prefersStatusBarHidden: Bool {
return true
}
override var supportedInterfaceOrientations: UIInterfaceOrientationMask {
return .portrait
}
}