摄像机视角调整

Question

我对Swift或Xcode不太了解，所以不胜感激！

我为我的QR /相机控制器制作了一个单独的.swift文件。我在网上找到了有关如何制作QR码阅读器的this教程，并输入了提供的代码，并且一切都很好，只是“相机视图”未正确显示在屏幕上（使用iPhone 8）。如何调整视频视图？

代码：

import UIKit

导入AVFoundation

类CameraController：UIViewController，UIImagePickerControllerDelegate，UINavigationControllerDelegate，AVCapturePhotoCaptureDelegate，AVCaptureMetadataOutputObjectsDelegate {

@IBOutlet weak var previewView: UIView!
@IBOutlet weak var lblOutput: UILabel!

var imageOrientation: AVCaptureVideoOrientation?
    var captureSession: AVCaptureSession?
    var videoPreviewLayer: AVCaptureVideoPreviewLayer?
    var capturePhotoOutput: AVCapturePhotoOutput?

    override func viewDidLoad() {
        super.viewDidLoad()

        // Get an instance of the AVCaptureDevice class to initialize a
        // device object and provide the video as the media type parameter
        guard let captureDevice = AVCaptureDevice.default(for: AVMediaType.video) else {
            fatalError("No video device found")
        }
        // handler chiamato quando viene cambiato orientamento
        self.imageOrientation = AVCaptureVideoOrientation.portrait

        do {
            // Get an instance of the AVCaptureDeviceInput class using the previous deivce object
            let input = try AVCaptureDeviceInput(device: captureDevice)

            // Initialize the captureSession object
            captureSession = AVCaptureSession()

            // Set the input device on the capture session
            captureSession?.addInput(input)

            // Get an instance of ACCapturePhotoOutput class
            capturePhotoOutput = AVCapturePhotoOutput()
            capturePhotoOutput?.isHighResolutionCaptureEnabled = true

            // Set the output on the capture session
            captureSession?.addOutput(capturePhotoOutput!)
            captureSession?.sessionPreset = .high

            // Initialize a AVCaptureMetadataOutput object and set it as the input device
            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 = [AVMetadataObject.ObjectType.qr]

            //Initialise 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
            previewView.layer.addSublayer(videoPreviewLayer!)

            //start video capture
            captureSession?.startRunning()

        } catch {
            //If any error occurs, simply print it out
            print(error)
            return
        }

    }

    override func viewWillAppear(_ animated: Bool) {
        navigationController?.setNavigationBarHidden(true, animated: false)
        self.captureSession?.startRunning()
    }

    // Find a camera with the specified AVCaptureDevicePosition, returning nil if one is not found
    func cameraWithPosition(position: AVCaptureDevice.Position) -> AVCaptureDevice? {
        let discoverySession = AVCaptureDevice.DiscoverySession(deviceTypes: [.builtInWideAngleCamera], mediaType: AVMediaType.video, position: .unspecified)
        for device in discoverySession.devices {
            if device.position == position {
                return device
            }
        }

        return nil
    }

    func metadataOutput(_ captureOutput: AVCaptureMetadataOutput,
                        didOutput metadataObjects: [AVMetadataObject],
                        from connection: AVCaptureConnection) {
        // Check if the metadataObjects array is contains at least one object.
        if metadataObjects.count == 0 {
            return
        }

        //self.captureSession?.stopRunning()

        // Get the metadata object.
        let metadataObj = metadataObjects[0] as! AVMetadataMachineReadableCodeObject

        if metadataObj.type == AVMetadataObject.ObjectType.qr {
            if let outputString = metadataObj.stringValue {
                DispatchQueue.main.async {
                    print(outputString)
                    self.lblOutput.text = outputString
                }
            }
        }

    }

}

当前视图的图像：