Xcode 9/Swift 4 AVCaptureMetadataOutput setMetadataObjectTypes使用availableMetadataObjectTypes

本文介绍了Xcode 9/Swift 4 AVCaptureMetadataOutput setMetadataObjectTypes使用availableMetadataObjectTypes的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

似乎有很多与我遇到的问题类似的问题:

There seems to be a lot of issues similar to what I am experiencing:

AVmetadata使用4 xcode 9快速更改

​​找到了AVCaptureMetadataOutput setMetadataObjectTypes不支持的类型

还有一个与AVFoundation相关的Apple错误:

And there is an Apple bug that deals with AVFoundation:

forums.developer.apple/thread/86810#259270

但是这些似乎都不是我的答案.我的代码在swift 3中可以很好地运行，但是在swift 4中只会出错.使用上述链接中的解决方案根本没有任何改变.

But none of those seem to actually be the answer for me. I have code that runs great in swift 3, but will only error out in swift 4. Using the solutions in the above links results in no change at all.

代码:

import UIKit import AVFoundation class BarCodeScanViewController: UIViewController, AVCaptureMetadataOutputObjectsDelegate { weak var delegate: FlowControllerDelegate? var captureSession: AVCaptureSession = AVCaptureSession() var previewLayer: AVCaptureVideoPreviewLayer = 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.canAddInput(videoInput) } else { failed() return } // let captureMetadataOutput = AVCaptureMetadataOutput() let metadataOutput = AVCaptureMetadataOutput() if captureSession.canAddOutput(metadataOutput) { captureSession.addOutput(metadataOutput) // Check status of camera permissions metadataOutput.setMetadataObjectsDelegate(self, queue: DispatchQueue.main) // metadataOutput.metadataObjectTypes = [AVMetadataObject.ObjectType.upce] metadataOutput.metadataObjectTypes = [.ean8, .ean13, .pdf417, .upce] } 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) { if captureSession.isRunning == true { captureSession.stopRunning() } super.viewWillDisappear(animated) } func captureOutput(_ captureOutput: AVCaptureOutput!, didOutputMetadataObjects metadataObjects: [Any]!, from connection: AVCaptureConnection!) { captureSession.stopRunning() if let metatdataObject = metadataObjects.first { guard let readableObject = metatdataObject 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 } }

当我在Xcode 8和Swift 3中构建此代码时，它可以正常工作.当我在Xcode 9中运行它时，Swift 4it在添加媒体类型时崩溃:

When I build this code in Xcode 8 and swift 3 it works fine. When I run it in Xcode 9 swift 4it crashes at adding the media types:

metadataOutput.metadataObjectTypes = [.ean8, .ean13, .pdf417, .upce]

在这两种情况下，我都将构建到以前没有Beta的iOS 11设备.

In both cases I am building to an iOS 11 device that did not have the beta on it previously.

我尝试使用"__"来查看是否是上面提到的Apple bug.如果我将代码行注释掉，则代码会运行，但是没有捕获.

I have tried the "__" to see if it was the Apple bug metioned above. If I comment the line out the code runs but there is not capture.

苹果可能还会引入其他错误吗?还有其他人遇到这个问题吗?

Is there some other bug Apple introduced maybe? Anyone else having this issue?

任何帮助将不胜感激.

谢谢

推荐答案

其他有关清晰度的信息:

Leevi Graham是正确的，也确实是苹果在没有适当文档的情况下更改了堆栈.这导致看起来好像有一个错误.

Leevi Graham is correct as well as it being true that Apple changed the stack without proper documentation. This results in it seeming like there is a bug.

条码为swift 4

澄清对我有帮助的评论

代表回叫已从以下方式更改:

The delegate call back has changed from:

func captureOutput(_ captureOutput: AVCaptureOutput!, didOutputMetadataObjects metadataObjects: [Any]!, from connection: AVCaptureConnection!)

到

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

但是，我真正遇到的问题是您不再设置一长串类型来获取您的 metadataObjectTypes .现在，您只需设置所有可用的类型:

HOWEVER, the real problem I was having was that you no longer set a long array of types to get your metadataObjectTypes. You now just set for all available types:

metadataOutput.metadataObjectTypes = metadataOutput.availableMetadataObjectTypes

所以...

这实际上是一个API问题.为此提出了若干雷达问题.但是苹果已经改变了他们的AVFoundation文档来解决这个问题.

This is, in fact an API issue. Several radar issues were filed for it. But Apple has Kindly changed their AVFoundation docs to address the issue.