问题描述
我正在尝试制作条形码扫描仪应用程序。相机会话一开始，应用程序就会在几秒钟内崩溃。 
我无法找到这背后的原因。以及如何解决这个问题。
我使用 https://www.appcoda.com/barcode-reader-swift/ 制作了 barcde 扫描仪。
import Foundation
import UIKit
import AVFoundation
import CoreData
enum BarcodeScanError : String{
case cameraLoadFailed = "Camera Load Failed"
case NovalidBarcode = "No Valid Barcode"
}
class ScanBoardingPassViewController : UIViewController {
//MARK: - Properties
var viewmodel : ScanBoardingPassviewmodel? = nil
var captureSession : AVCaptureSession?
var videoPreviewLayer: AVCaptureVideoPreviewLayer?
var qrCodeFrameView: UIView?
private let supportedCodeTypes = [AVMetadataObject.ObjectType.aztec,AVMetadataObject.ObjectType.pdf417]
//MARK: - Outlets
@IBOutlet weak var btnCancel: UIButton!
//MARK: - View Life Cycle
override func viewDidLoad() {
viewmodel = ScanBoardingPassviewmodel()
self.captureSession = AVCaptureSession()
self.setUpView()
super.viewDidLoad()
}
override func viewWilldisappear(_ animated: Bool) {
super.viewWilldisappear(true)
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// dispose of any resources that can be recreated.
}
//MARK: - Set Up View
func setUpView() {
self.setUpBarCodeScanner()
self.view.bringSubviewToFront(self.btnCancel)
self.setUpBarcodeRecognizerFrame()
}
private func setUpBarCodeScanner() {
// Get the back-facing camera for capturing videos
guard let captureDevice = AVCaptureDevice.default(for: AVMediaType.video) else {
debugPrint(BarcodeScanError.cameraLoadFailed)
return
}
do {
// Get an instance of the AVCaptureDeviceInput class using the prevIoUs device object.
let input = try AVCaptureDeviceInput(device: captureDevice)
// Set the input device on the capture session.
captureSession?.addInput(input)
// Initialize a AVCaptureMetadataOutput object and set it as the output device to the capture session.
let captureMetadataOutput = AVCaptureMetadataOutput()
captureSession?.addOutput(captureMetadataOutput)
// Set delegate and use the default dispatch queue to execute the call back
captureMetadataOutput.setMetadataObjectsDelegate(self,queue: dispatchQueue.main)
captureMetadataOutput.MetadataObjectTypes = supportedCodeTypes
// captureMetadataOutput.MetadataObjectTypes = [AVMetadataObject.ObjectType.qr]
} catch {
// If any error occurs,simply print it out and don't continue any more.
print(error)
return
}
// Initialize the video preview layer and add it as a sublayer to the viewPreview view's layer.
videoPreviewLayer = AVCaptureVideoPreviewLayer(session: captureSession!)
videoPreviewLayer?.videoGravity = AVLayerVideoGravity.resizeAspectFill
videoPreviewLayer?.frame = view.layer.bounds
view.layer.addSublayer(videoPreviewLayer!)
// Start video capture.
captureSession?.startRunning()
}
private func setUpBarcodeRecognizerFrame() {
// Initialize QR Code Frame to highlight the QR code
qrCodeFrameView = UIView()
if let qrCodeFrameView = qrCodeFrameView {
qrCodeFrameView.layer.borderColor = UIColor.green.cgColor
qrCodeFrameView.layer.borderWidth = 2
view.addSubview(qrCodeFrameView)
view.bringSubviewToFront(qrCodeFrameView)
}
}
//MARK: - Outlets
@IBAction func btnCancelpressed(_ sender: UIButton) {
self.dismissView()
}
func dismissView() {
self.dismiss(animated: true,completion: nil)
}
}
extension ScanBoardingPassViewController: AVCaptureMetadataOutputObjectsDelegate {
func MetadataOutput(_ output: AVCaptureMetadataOutput,didOutput MetadataObjects: [AVMetadataObject],from connection: AVCaptureConnection) {
// Check if the MetadataObjects array is not nil and it contains at least one object.
if MetadataObjects.count == 0 {
qrCodeFrameView?.frame = CGRect.zero
debugPrint(BarcodeScanError.NovalidBarcode)
return
}
// Get the Metadata object.
let MetadataObj = MetadataObjects[0] as! AVMetadataMachineReadableCodeObject
if supportedCodeTypes.contains(MetadataObj.type) {
// If the found Metadata is equal to the QR code Metadata (or barcode) then update the status label's text and set the bounds
let barCodeObject = videoPreviewLayer?.transformedMetadataObject(for: MetadataObj)
qrCodeFrameView?.frame = barCodeObject!.bounds
if MetadataObj.stringValue != nil {
captureSession?.stopRunning()
debugPrint("Valid Barcode found \(MetadataObj.stringValue!)")
if let boardingPass = viewmodel?.parseBoardingPassstring(boardingPassstring : MetadataObj.stringValue!) {
let unitOfWork = UnitOfWork(context:( UIApplication.shared.delegate as! AppDelegate).persistentContainer.newBackgroundContext() )
unitOfWork.boardingPassRepository.saveBoardingPasses(boardingPass: boardingPass)
unitOfWork.saveChanges()
print(unitOfWork.boardingPassRepository.getBoardingPasses(predicate: nil))
self.dismissView()
}
}
}
}
}
相机不会被击中。但是，该应用程序每次都会在几秒钟内给出一个 lldb。
解决方法
// Created by Satya Narayana on 17/11/20.
//
import UIKit
import AVFoundation
import UIKit
class QRViewController: UIViewController,AVCaptureMetadataOutputObjectsDelegate {
//MARK: Outlets
@IBOutlet weak var qrLbl: UILabel! // BarCode displaying Label
@IBOutlet weak var sView: UIView! // View
//MARK: Variables
var captureSession: AVCaptureSession!
var previewLayer: AVCaptureVideoPreviewLayer!
//MARK: View Methods
override func viewDidLoad() {
super.viewDidLoad()
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,.ean13,.code128]
} else {
failed()
return
}
previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
previewLayer.frame = sView.layer.bounds
previewLayer.videoGravity = .resizeAspectFill
sView.layer.addSublayer(previewLayer)
captureSession.startRunning()
}
func failed() {
self.showToast(message: "Scanning not supported.Your device does not support scanning a code from an item. Please use a device with a camera.",seconds: 1.0)
captureSession = nil
}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
qrLbl.isHidden = true
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)
}
//MARK:- Found BARCODE
func found(code: String) {
print(code)
if code != ""{
print(code) // This is Barcode
qrLbl.text = code
}else{
// if you need run again uncomment below line
//self.captureSession.startRunning()
}
}
override var supportedInterfaceOrientations: UIInterfaceOrientationMask {
return .portrait
}
}