没有活动和启用的视频连接，以前的解决方案不起作用

Question

我正在构建一个自定义相机应用程序，当我按“拍照”按钮时，它会一直显示给我

  

“没有有效的视频连接”。

我认为这是委派问题，但我不确定要解决的问题。

我在堆栈中尝试了其他解决方案，但没有一个起作用。我是Swift的新手，所以详细的答案将非常有帮助。

  @IBOutlet weak var imageView: UIView!
  @IBOutlet weak var outputImageView: UIImageView!
  @IBAction func takePhotoBtnPressed(_ sender: Any) {
    let settings = AVCapturePhotoSettings(format: [AVVideoCodecKey: AVVideoCodecType.jpeg])
    stillImageOutput!.capturePhoto(with: settings, delegate: self)
  }
 func photoOutput(_ output: AVCapturePhotoOutput, didFinishProcessingPhoto photo: AVCapturePhoto, error: Error?) {

    guard let imageData = photo.fileDataRepresentation()
      else { return }

    let image = UIImage(data: imageData)
    outputImageView.image = image
  }
 override func viewWillDisappear(_ animated: Bool) {
    super.viewWillDisappear(animated)
    self.session!.stopRunning()
  }

 override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)
    session = AVCaptureSession()
    session.sessionPreset = .low
    guard let backCamera = AVCaptureDevice.default(for: AVMediaType.video)
      else {
        print("Unable to access back camera!")
        return
    }

    do {
      let input = try AVCaptureDeviceInput(device: backCamera)
      stillImageOutput = AVCapturePhotoOutput()
      if session.canAddInput(input) && session.canAddOutput(stillImageOutput) {
        session.addInput(input)
        session.addOutput(stillImageOutput)
        setupLivePreview()
      }
    }
    catch let error  {
      print("Error Unable to initialize back camera:  \(error.localizedDescription)")
    }
    stillImageOutput = AVCapturePhotoOutput()
  }

func setupLivePreview() {
    videoPreviewLayer = AVCaptureVideoPreviewLayer(session: session)
    videoPreviewLayer.videoGravity = .resizeAspectFill
    videoPreviewLayer.connection?.videoOrientation = .portrait
    imageView.layer.addSublayer(videoPreviewLayer)

    DispatchQueue.global(qos: .userInitiated).async { //[weak self] in
      self.session.startRunning()
      DispatchQueue.main.async {
        self.videoPreviewLayer.frame = self.imageView.bounds
      }
    }
  }

 override func viewDidLoad() {
    super.viewDidLoad()

    if AVCaptureDevice.authorizationStatus(for: .video) ==  .authorized {
      print("yes auth")
    } else {
      AVCaptureDevice.requestAccess(for: .video, completionHandler: { (granted: Bool) in
        if granted {

        } else {
          print("no auth")
        }
      })
    }

  }
}

它的错误消息是：

  

由于未捕获的异常“ NSGenericException”而终止应用程序，原因：“ ***-[AVCapturePhotoOutput capturePhotoWithSettings：delegate：]没有活动和启用的视频连接”