相机条码扫描适用于 iPhone，但不适用于 iPad

Question

我正在使用 AVCaptureDevice API 扫描条码，它在 iPhone 上运行良好，但非常相似的代码在 iPad 上无法运行，我不太清楚为什么（根本没有检测到任何条码）。主要区别在于扫描区域的大小、位置和方向。我使用 iPhone 12 mini（iOS 15 测试版）和原始 iPad Pro 9.7"（iOS 14.6）进行了测试。不确定这是否重要。

以下是扫描仪的代码。如果您发现需要更改的内容，请告诉我。

import Foundation
import AVFoundation
import UIKit

class ScannerViewController: UIViewController, AVCaptureMetadataOutputObjectsDelegate {
    var captureSession: AVCaptureSession!
    var previewLayer: AVCaptureVideoPreviewLayer!
    var barcodeCallback: (String) -> Void
    var cameraScanDismissedCallback: (Bool) -> Void
    var scanned = false
    var currentDevice: AVCaptureDevice!
    var scanRectView: UIView!

    init(barcodeCallback: @escaping (String) -> Void, cameraScanDismissedCallback: @escaping (Bool) -> Void) {
        self.barcodeCallback = barcodeCallback;
        self.cameraScanDismissedCallback = cameraScanDismissedCallback;
        super.init(nibName: nil, bundle: nil)
    }

    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    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, .ean8, .ean13, .pdf417, .code128, .aztec, .code39, .code39Mod43, .code93, .dataMatrix, .face, .interleaved2of5, .itf14, .upce]
        } else {
            failed()
            return
        }
    
        let windowSize = UIScreen.main.bounds.size
    
        var scanSize: CGSize!;
        var scanRect: CGRect!;
        if(UIDevice.current.userInterfaceIdiom == .pad){
            scanSize = CGSize(width:windowSize.width*1/3, height:windowSize.width*1/7);
            scanRect = CGRect(x: UIScreen.main.bounds.midX - scanSize.width/2,
                          y: UIScreen.main.bounds.midY - scanSize.height/2,
                          width:scanSize.width, height:scanSize.height);
        }else{
            scanSize = CGSize(width:windowSize.width*2/3, height:windowSize.width*1/3);
            scanRect = CGRect(x: UIScreen.main.bounds.midX - scanSize.width/2,
                          y: UIScreen.main.bounds.midY - scanSize.height/2,
                          width:scanSize.width, height:scanSize.height);
        }
    
        scanRect = CGRect(x:scanRect.origin.y/windowSize.height,
                      y:scanRect.origin.x/windowSize.width,
                      width:scanRect.size.height/windowSize.height,
                      height:scanRect.size.width/windowSize.width);
        metadataOutput.rectOfInterest = scanRect

        previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
    
        if(UIDevice.current.userInterfaceIdiom == .pad){
            let orientation: UIDeviceOrientation = UIDevice.current.orientation
            previewLayer.connection?.videoOrientation = {
                switch (orientation) {
                case .faceUp:
                    return .landscapeLeft
                case .portrait:
                    return .portrait
                case .landscapeRight:
                    return .landscapeLeft
                case .landscapeLeft:
                    return .landscapeRight
                default:
                    return .portrait
                }
            }()
        }
    
        previewLayer.frame = view.layer.bounds
        previewLayer.videoGravity = .resizeAspectFill
        view.layer.addSublayer(previewLayer)
    
        scanRectView = UIView();
        view.addSubview(self.scanRectView)
        scanRectView.frame = CGRect(x:0, y:0, width: scanSize.width,
                                     height: scanSize.height);
    
        if(UIDevice.current.userInterfaceIdiom == .pad){
            scanRectView.center = CGPoint( x:UIScreen.main.bounds.midX - scanSize.width/2,
                                            y:UIScreen.main.bounds.midY - scanSize.height/2)
        }else{
            scanRectView.center = CGPoint( x:UIScreen.main.bounds.midX,
                                       y:UIScreen.main.bounds.midY)
        }
    
        scanRectView.layer.borderColor = UIColor.yellow.cgColor
        scanRectView.layer.borderWidth = 5;

        currentDevice = videoCaptureDevice
        captureSession.startRunning()
        toggleTorch(on: true)
    }

    func toggleTorch(on: Bool) {
        guard let device = currentDevice else { return }

        if device.hasTorch {
            do {
                try device.lockForConfiguration()
            
                if(UIDevice.current.userInterfaceIdiom == .pad){
                    device.videoZoomFactor = 1.3
                }else{
                    device.videoZoomFactor = 1.5
                }

                if on == true {
                    device.torchMode = .on
                } else {
                    device.torchMode = .off
                }

                device.unlockForConfiguration()
            } catch {
                print("Torch could not be used")
            }
        } else {
            print("Torch is not available")
        }
    }

    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
        toggleTorch(on: false)
    }

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)

        if (captureSession?.isRunning == false) {
            captureSession.startRunning()
            toggleTorch(on: true)
        }
    }

    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)

        if (captureSession?.isRunning == true) {
            captureSession.stopRunning()
            toggleTorch(on: false)
        }
    
        cameraScanDismissedCallback(scanned)
    }

    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)
            scanned = true
        }

        dismiss(animated: true)
    }

    func found(code: String) {
        print(code)
        barcodeCallback(code)
    }

    override var prefersStatusBarHidden: Bool {
        return true
    }

    override var supportedInterfaceOrientations: UIInterfaceOrientationMask {
        if(UIDevice.current.userInterfaceIdiom == .pad){
            return .landscape
        }else{
            return .portrait
        }
    }
}

Answer 1

以防万一有人遇到类似问题，请检查以下内容：

1. 视频的方向
2. AVCaptureMetadataOutput.rectOfInterest的位置

我仍然遇到 rectOfInterest 未位于中心的问题，但它可以工作。一旦我弄清楚如何将其居中，我将在此处发布解决方案。

Answer 2

它不是中心可能是因为您的导航栏。 尝试如下设置rectOfInterest，记住camer使用的坐标与UIView不同，posX和posY在UIView坐标中

let aimRect = CGRect(x: (posY - navBar.height) / UIScreen.main.bounds.height,
                     y: posX / UIScreen.main.bounds.width,
                     width: rectHeight / UIScreen.main.bounds.height,
                     height: rectWidth / UIScreen.main.bounds.width)