在条形码扫描器应用程序的相机视图上添加对象 (Swift 3)

Question

在我的故事板上，我有一个视图控制器，它具有以下 class 关联：

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()

        let videoCaptureDevice = AVCaptureDevice.defaultDevice(withMediaType: AVMediaTypeVideo)
        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 = [AVMetadataObjectTypeEAN8Code, AVMetadataObjectTypeEAN13Code, AVMetadataObjectTypePDF417Code, AVMetadataObjectTypeCode39Code]
        } else {
            failed()
            return
        }

        previewLayer = AVCaptureVideoPreviewLayer(session: captureSession);
        previewLayer.frame = view.layer.bounds;
        previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;
        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 captureOutput(_ captureOutput: AVCaptureOutput!, didOutputMetadataObjects metadataObjects: [Any]!, from connection: AVCaptureConnection!) {
        captureSession.stopRunning()

        let initialView: PLLogViewController = presentingViewController as! PLLogViewController

        if let metadataObject = metadataObjects.first {
            let readableObject = metadataObject as! AVMetadataMachineReadableCodeObject;

            AudioServicesPlaySystemSound(SystemSoundID(kSystemSoundID_Vibrate))
            found(code: readableObject.stringValue);
            initialView.setResults(code: readableObject.stringValue)
        }

        dismiss(animated: true)
    }

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

    override var supportedInterfaceOrientations: UIInterfaceOrientationMask {
        return .portrait
    }
}

这段代码基本上启动了一个充当条形码扫描仪的相机视图。如果您将设备指向条形码，它会检测条形码，并将结果推送到文本字段。

这一切都很好。我的问题是 - 我想在屏幕上显示一些其他元素。现在，我的整个屏幕都被相机占据了，所以如果你访问这个视图，你要么必须扫描条形码，要么你必须关闭应用程序。

我试图通过从对象库中拖动其他元素来将它们添加到视图中，但是，相机似乎覆盖了这些项目，使它们无法访问。

我想在相机视图的顶部添加两个元素。第一个是图像，看起来像 "bracket" 以指示用户应该 "fit" 他们正在扫描的条形码。

第二个是允许用户取消相机视图的按钮。

所以最终，我的问题很简单，如何在以编程方式初始化的相机视图之上添加元素？

Answer 1

如果您希望显示视频预览，请在您的视图控制器中添加一个视图，然后只需将预览层添加到该层而不是整个视图。

像这样：

// 初始化视频预览层并将其作为子层添加到您的视图层。

    previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
    previewLayer?.videoGravity = AVLayerVideoGravityResizeAspectFill
    previewLayer?.frame = /*your views name here i e qrView*/.layer.bounds
    /*your views name here i e qrView*/.layer.addSublayer(videoPreviewLayer!)

// 而不是

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

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