iOS App因相机权限崩溃：已配置NSCameraUsageDescription仍报错

问题背景 #

打开二维码扫描视图控制器时App直接崩溃，报错内容如下：

This app has crashed because it attempted to access privacy-sensitive data without a usage description. The app's Info.plist must contain an NSCameraUsageDescription key with a string value explaining to the user how the app uses this data.

已反复检查Info.plist文件及Target配置，确认添加了相机权限描述，但错误仍未解决。相关ViewController代码如下：

import UIKit
import AVFoundation

class Scanner__VC: 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 = [.qr]
        } 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
    }

    func showAlert(with message: String) {
        let alert = UIAlertController(title: "QR Code Scanned", message: message, preferredStyle: .alert)
        alert.addAction(UIAlertAction(title: "OK", style: .default))
        present(alert, animated: true)
    }
}

可能的遗漏配置及修复方案 #

• 检查权限键名拼写：确保Info.plist中添加的是NSCameraUsageDescription（注意大小写和完整拼写，避免少写字母或写错单词），iOS 10及以上版本必须使用该键名。
• 确认配置文件对应正确Target：项目中可能存在多个Info.plist（如主App、Extension的配置），需验证添加权限的是当前运行Target对应的Info.plist。可通过Target的「Build Settings」→「Info.plist File」路径确认文件位置。
• 保证权限描述非空：权限对应的字符串值不能为空，必须填写明确的用途说明（例如“需要访问相机以扫描二维码”），空值会被系统判定为未配置权限。
• 清理缓存并重启Xcode：Xcode可能缓存旧配置，执行「Product」→「Clean Build Folder」，重启Xcode后重新编译运行。
• 调整权限申请时机：代码中在viewDidLoad直接启动captureSession.startRunning()，但iOS要求权限弹窗需由用户交互触发（如按钮点击）。建议将相机启动逻辑移至用户主动操作（比如点击“开始扫描”按钮）之后，避免系统拦截权限申请。
• 验证编译后包的配置：右键点击编译生成的.app文件→「Show Package Contents」，打开其中的Info.plist，确认NSCameraUsageDescription键和对应值是否存在，验证配置是否被正确打包。

内容的提问来源于stack exchange，提问作者Hamza Imran