iOS Swift - How to use rectOfInterest correctly (barcode scanner) - ios

Question

I have an iOS App which scans a barcode.
Now I wanted to define a specific scan area. For this purpose I am using the rectOfInterest property and metadataOutputRectOfInterest method.
The problems I face
When I use just this code below nothing will be scanned, if I remove barcodeAreaView scanning works fine all over the display
class BarcodeReaderViewController: UIViewController, AVCaptureMetadataOutputObjectsDelegate {
// Camera view
var cameraView: AVCaptureVideoPreviewLayer?
// AV capture session and dispatch queue
let captureSession = AVCaptureSession()
let sessionQueue = DispatchQueue(label: AVCaptureSession.self.description(), attributes: [], target: nil)
var barcodeAreaView: UIView?
let supportedCodeTypes = [
AVMetadataObjectTypeEAN8Code,
AVMetadataObjectTypeEAN13Code,
AVMetadataObjectTypeUPCECode,
AVMetadataObjectTypeCode39Code,
AVMetadataObjectTypeCode93Code,
AVMetadataObjectTypeCode128Code,
AVMetadataObjectTypeCode39Mod43Code,
AVMetadataObjectTypeInterleaved2of5Code
]
let metadataOutput = AVCaptureMetadataOutput()
var barcodeArea:CGRect!
override func viewDidLoad() {
super.viewDidLoad()
let width = 250
let height = 100
print(self.view.frame.size.width)
let xPos = (CGFloat(self.view.frame.size.width) / CGFloat(2)) - (CGFloat(width) / CGFloat(2))
let yPos = (CGFloat(self.view.frame.size.height) / CGFloat(2)) - (CGFloat(height) / CGFloat(2))
barcodeArea = CGRect(x: Int(xPos), y: Int(yPos), width: width, height: height)
barcodeAreaView = UIView()
barcodeAreaView?.layer.borderColor = UIColor.red.cgColor
barcodeAreaView?.layer.borderWidth = 1
barcodeAreaView?.frame = barcodeArea
view.addSubview(barcodeAreaView!)
captureSession.beginConfiguration()
let videoDevice = AVCaptureDevice.defaultDevice(withMediaType: AVMediaTypeVideo)
if videoDevice != nil {
let videoDeviceInput = try? AVCaptureDeviceInput(device: videoDevice)
if videoDeviceInput != nil {
if captureSession.canAddInput(videoDeviceInput) {
captureSession.addInput(videoDeviceInput)
}
}
if captureSession.canAddOutput(metadataOutput) {
captureSession.addOutput(metadataOutput)
metadataOutput.metadataObjectTypes = supportedCodeTypes
metadataOutput.setMetadataObjectsDelegate(self, queue: DispatchQueue.main)
cameraView = AVCaptureVideoPreviewLayer(session: captureSession)
cameraView?.videoGravity = AVLayerVideoGravityResizeAspectFill
cameraView?.frame = view.layer.bounds
metadataOutput.rectOfInterest = cameraView!.metadataOutputRectOfInterest(for: barcodeArea)
view.layer.addSublayer(cameraView!)
}
}
captureSession.commitConfiguration()
view.bringSubview(toFront: barcodeAreaView!)
}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
// Start AV capture session
sessionQueue.async {
self.captureSession.startRunning()
}
}
override func viewWillDisappear(_ animated: Bool) {
super.viewWillDisappear(animated)
// Stop AV capture session
sessionQueue.async {
self.captureSession.stopRunning()
}
}
func captureOutput(_ captureOutput: AVCaptureOutput!, didOutputMetadataObjects metadataObjects: [Any]!, from connection: AVCaptureConnection!) {
if let metadataObject = metadataObjects.first {
let readableObject = metadataObject as! AVMetadataMachineReadableCodeObject
let message = readableObject.stringValue
print(message)
}
}
}
I already took a look on this question
How do I use the metadataOutputRectOfInterestForRect method and rectOfInterest property to scan a specific area? (QR Code)
The problem I face here, the scan is a bit laggy and my navigationController is not working (because the listener awaits a scan)
UPDATE:
solved the issue, as suggested in this answer
https://stackoverflow.com/a/37603743/2319900
I added the following line right after my self.captureSession.startRunning()
metadataOutput.rectOfInterest = cameraView!.metadataOutputRectOfInterest(for: barcodeArea)