条形码扫描后，屏幕冻结

Question

我正在学习 SWIFT 并且越来越好。我拥有的条形码应用程序可以工作，但它会无休止地扫描条形码，直到我强制弹出屏幕"确定"，"取消"以接受或拒绝扫描。在研究中，我发现了非常相似的代码(如下所示(。因此，我创建了一个只有一个视图控制器的测试项目来尝试此代码。它工作得很好，但一旦扫描条形码就会冻结。我的目的是解冻屏幕，接受并保存它，并允许用户扫描更多条形码。任何帮助将不胜感激。我尝试在找到的行(代码：(下方停止扫描，但它无助于解冻。我可能是错的，但我怀疑视线从来不会被叫到这里。

---

import AVFoundation
import UIKit
class ScannerViewController: UIViewController, AVCaptureMetadataOutputObjectsDelegate {
var captureSession: AVCaptureSession!
var previewLayer: AVCaptureVideoPreviewLayer!
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 = [.ean8, .ean13, .pdf417]
} else {
failed()
return
}
previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
previewLayer.frame = view.layer.bounds
previewLayer.videoGravity = .resizeAspectFill
view.layer.addSublayer(previewLayer)
captureSession.startRunning()
}
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
}
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) {
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)
}
func found(code: String) {
print(code)
}
override var prefersStatusBarHidden: Bool {
return true
}
override var supportedInterfaceOrientations: UIInterfaceOrientationMask {
return .portrait
}

}

---

编辑的代码：

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)
barcodeValue = stringValue
}
// dismiss(animated: true)
previewLayer.removeFromSuperlayer()
previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
previewLayer.frame = view.layer.bounds
previewLayer.videoGravity = .resizeAspectFill
view.layer.addSublayer(previewLayer)
let alertController = UIAlertController(title: "Barcode Scanned", message: barcodeValue!, preferredStyle: .alert)
alertController.addAction(UIAlertAction(title: "OK", style: .default, handler: {(alert: UIAlertAction!) in self.restartScan()}))
alertController.addAction(UIAlertAction(title: "Cancel", style: .cancel, handler:nil))
present(alertController, animated: true, completion: nil)
//captureSession.startRunning()
}
func found(code: String) {
print(code)
}
func restartScan() {
captureSession.startRunning()
}

Answer 1

这不是冻结，当检测到第一个条形码时，您需要这个，您会停止带有内部captureSession.stopRunning()func metadataOutput(_ output: AVCaptureMetadataOutput

previewLayer.removeFromSuperlayer()

而不是这个

dismiss(animated: true)

因为它是一个层，而不是您之前添加的要关闭的 VC

view.layer.addSublayer(previewLayer)

注意：视图背景为黑色