AVFoundation、DataMatrix、Swift 4

Question

呃。我与 Swift 4 AVFoundation 的变化斗争仍在继续。

我有一个数据矩阵 "QR" 代码，我正在尝试阅读。

它在 Swift 3 编译时读起来很好，但在 Swift 4 代码更改后它没有被拾取。

另请注意，Apple 提供的本应与 Swift 4 一起使用的示例也不会读取 DataMatrix 代码

当我打印出可用类型时，Data Matrix 可用。

print("types available:\n \(metadataOutput.availableMetadataObjectTypes)")

产量：

types available:
[__ObjC.AVMetadataObject.ObjectType(_rawValue: face), ... 
__ObjC.AVMetadataObject.ObjectType(_rawValue: org.iso.DataMatrix), ...

但是，当我运行代码时，didOutput metadataObjects: 从未被调用。但是，它确实会被其他类型调用。

另外明确添加类型：

metadataOutput.metadataObjectTypes = [AVMetadataObject.ObjectType.dataMatrix]

没什么不同。

有人在 Swift 4 中扫描过 DataMatrix 吗？

代码：

import UIKit
import AVFoundation

class ViewController: UIViewController,AVCaptureMetadataOutputObjectsDelegate {

var videoCaptureDevice: AVCaptureDevice = AVCaptureDevice.default(for: AVMediaType.video)!
var device = AVCaptureDevice.default(for: AVMediaType.video)
var output = AVCaptureMetadataOutput()
var previewLayer: AVCaptureVideoPreviewLayer?

var captureSession = AVCaptureSession()
var code: String?

var scannedCode = UILabel()

override func viewDidLoad() {
    super.viewDidLoad()

    self.setupCamera()
    self.addLabelForDisplayingCode()
}

private func setupCamera() {

    let input = try? AVCaptureDeviceInput(device: videoCaptureDevice)

    if self.captureSession.canAddInput(input!) {
        self.captureSession.addInput(input!)
    }

    self.previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)

    if let videoPreviewLayer = self.previewLayer {
        videoPreviewLayer.videoGravity = AVLayerVideoGravity.resizeAspectFill
        videoPreviewLayer.frame = self.view.bounds
        view.layer.addSublayer(videoPreviewLayer)
    }

    let metadataOutput = AVCaptureMetadataOutput()
    if self.captureSession.canAddOutput(metadataOutput) {
        self.captureSession.addOutput(metadataOutput)

        metadataOutput.setMetadataObjectsDelegate(self, queue: DispatchQueue.main)

        print("types available:\n \(metadataOutput.availableMetadataObjectTypes)")

        metadataOutput.metadataObjectTypes = metadataOutput.availableMetadataObjectTypes
//            metadataOutput.metadataObjectTypes = [AVMetadataObject.ObjectType.dataMatrix]
    } else {
        print("Could not add metadata output")
    }
}

private func addLabelForDisplayingCode() {
    view.addSubview(scannedCode)
    scannedCode.translatesAutoresizingMaskIntoConstraints = false
    scannedCode.bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: -20.0).isActive = true
    scannedCode.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 20.0).isActive = true
    scannedCode.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: -20.0).isActive = true
    scannedCode.heightAnchor.constraint(equalToConstant: 50).isActive = true
    scannedCode.font = UIFont.preferredFont(forTextStyle: .title2)
    scannedCode.backgroundColor = UIColor.black.withAlphaComponent(0.5)
    scannedCode.textAlignment = .center
    scannedCode.textColor = UIColor.white
    scannedCode.text = "Scanning...."
}

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

    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) {
    print(metadataObjects)
    for metadata in metadataObjects {
        let readableObject = metadata as! AVMetadataMachineReadableCodeObject
        let code = readableObject.stringValue
        scannedCode.text = code

    }
}
}

非常感谢。

Answer 1

您必须确保连接未被镜像。需要以原始格式读取数据矩阵。

https://developer.apple.com/documentation/avfoundation/avcaptureconnection/1389172-isvideomirrored

AVFoundation、DataMatrix、Swift 4

AVFoundation, DataMatrix, Swift 4

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