iOS 扫描二维码成功后如何关闭相机Swift 4

Question

扫描二维码成功后如何关闭相机？我的问题是当我从二维码扫描代码时，扫描后相机没有关闭。我怎样才能关闭相机？我的代码：

var captureSession: AVCaptureSession!
var previewLayer: AVCaptureVideoPreviewLayer!
var qrCode = String()

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
    }

    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)
        qrCode = code
    }

    override var prefersStatusBarHidden: Bool {
        return true
    }

    override var supportedInterfaceOrientations: UIInterfaceOrientationMask {
        return .portrait
    }

打开相机的按钮：

 @IBAction func scanQrButton(_ sender: Any) {
    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]
    } else {
        failed()
        return
    }

    previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
    previewLayer.frame = view.layer.bounds
    previewLayer.videoGravity = .resizeAspectFill
    view.layer.addSublayer(previewLayer)

    captureSession.startRunning()
}

如您所见，我有打开相机和扫描二维码的代码，但我想在没有 segue 的情况下扫描代码后关闭相机。

Answer 1

你试过吗？

self.captureSession?.stopRunning()

Answer 2

执行扫描后，您可以在会话中使用实例方法 stopRunning() 来停止捕获：

captureSession.stopRunning()

然后用相机输出的预览关闭视图（我认为这里的 removeFromSuperlayer() 会起作用）。您可以使用以下方法检测 AVCaptureMetadataOutputObjectsDelegate 提供的二维码何时被扫描：

optional func metadataOutput(_ output: AVCaptureMetadataOutput, didOutput metadataObjects: [AVMetadataObject], from connection: AVCaptureConnection)

您还应该将 startRunning() 放在串行队列中，如 Apple 文档所述：

The startRunning() method is a blocking call which can take some time, therefore you should perform session setup on a serial queue so that the main queue isn't blocked (which keeps the UI responsive).

iOS 扫描二维码成功后如何关闭相机Swift 4

iOS How to close camera after successfully scanning QR code Swift 4

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