我正在开发一个非常简单的视频应用程序。我使用官方控件：UIImagePickerController。

这是问题所在。首次显示UIImagePickerController时，iOS将请求权限。用户可以单击“是”或“否”。如果用户单击否，则不会关闭该控件。相反，如果用户一直单击“开始”按钮，则计时器将在屏幕始终为黑屏时继续运行，并且用户无法停止计时器或返回计时器。用户唯一能做的就是杀死该应用程序。下次呈现UIImagePickerController时，它仍然是黑屏，并且如果单击开始，则用户无法返回。

我想知道这是否是错误。有什么方法可以检测到摄像机的权限，以便我们决定是否显示UIImagePickerController？

检查AVAuthorizationStatus并正确处理案件。

NSString *mediaType = AVMediaTypeVideo;
AVAuthorizationStatus authStatus = [AVCaptureDevice authorizationStatusForMediaType:mediaType];
if(authStatus == AVAuthorizationStatusAuthorized) {
  // do your logic
} else if(authStatus == AVAuthorizationStatusDenied){
  // denied
} else if(authStatus == AVAuthorizationStatusRestricted){
  // restricted, normally won't happen
} else if(authStatus == AVAuthorizationStatusNotDetermined){
  // not determined?!
  [AVCaptureDevice requestAccessForMediaType:mediaType completionHandler:^(BOOL granted) {
    if(granted){
      NSLog(@"Granted access to %@", mediaType);
    } else {
      NSLog(@"Not granted access to %@", mediaType);
    }
  }];
} else {
  // impossible, unknown authorization status
}

Swift 4及更高版本

确保：

import AVFoundation

下面的代码检查所有可能的权限状态：

let cameraMediaType = AVMediaType.video
let cameraAuthorizationStatus = AVCaptureDevice.authorizationStatus(for: cameraMediaType)
    
switch cameraAuthorizationStatus {
case .denied: break
case .authorized: break
case .restricted: break

case .notDetermined:
    // Prompting user for the permission to use the camera.
    AVCaptureDevice.requestAccess(for: cameraMediaType) { granted in
        if granted {
            print("Granted access to \(cameraMediaType)")
        } else {
            print("Denied access to \(cameraMediaType)")
        }
    }
}

从iOS 10开始，您需要NSCameraUsageDescription在Info.plist中指定 密钥才能请求摄像头访问，否则您的应用程序将在运行时崩溃。请参阅需要使用说明的API。

作为一个有趣的旁注，您是否知道在设置中更改其摄像头权限时，如果iOS正在运行，iOS会终止该应用程序？

从Apple Developer论坛：

如果用户在“设置”中切换您的应用对摄像头的访问权限，则系统实际上会杀死您的应用。这同样适用于“设置”→“隐私”部分中的所有受保护数据类。

快速解决方案

extension AVCaptureDevice {
    enum AuthorizationStatus {
        case justDenied
        case alreadyDenied
        case restricted
        case justAuthorized
        case alreadyAuthorized
        case unknown
    }

    class func authorizeVideo(completion: ((AuthorizationStatus) -> Void)?) {
        AVCaptureDevice.authorize(mediaType: AVMediaType.video, completion: completion)
    }

    class func authorizeAudio(completion: ((AuthorizationStatus) -> Void)?) {
        AVCaptureDevice.authorize(mediaType: AVMediaType.audio, completion: completion)
    }

    private class func authorize(mediaType: AVMediaType, completion: ((AuthorizationStatus) -> Void)?) {
        let status = AVCaptureDevice.authorizationStatus(for: mediaType)
        switch status {
        case .authorized:
            completion?(.alreadyAuthorized)
        case .denied:
            completion?(.alreadyDenied)
        case .restricted:
            completion?(.restricted)
        case .notDetermined:
            AVCaptureDevice.requestAccess(for: mediaType, completionHandler: { (granted) in
                DispatchQueue.main.async {
                    if granted {
                        completion?(.justAuthorized)
                    } else {
                        completion?(.justDenied)
                    }
                }
            })
        @unknown default:
            completion?(.unknown)
        }
    }
}

然后为了使用它

AVCaptureDevice.authorizeVideo(completion: { (status) in
   //Your work here
})

除了@Raptor的答案外，还应提及以下内容。从iOS 10开始，您可能会收到以下错误：This application is modifying the autolayout engine from a background thread after the engine was accessed from the main thread. This can lead to engine corruption and weird crashes.

要解决此问题，请确保按以下方式处理主线程的结果（Swift 3）：

private func showCameraPermissionPopup() {
    let cameraMediaType = AVMediaTypeVideo
    let cameraAuthorizationStatus = AVCaptureDevice.authorizationStatus(forMediaType: cameraMediaType)

    switch cameraAuthorizationStatus {
    case .denied:
        NSLog("cameraAuthorizationStatus=denied")
        break
    case .authorized:
        NSLog("cameraAuthorizationStatus=authorized")
        break
    case .restricted:
        NSLog("cameraAuthorizationStatus=restricted")
        break
    case .notDetermined:
        NSLog("cameraAuthorizationStatus=notDetermined")

        // Prompting user for the permission to use the camera.
        AVCaptureDevice.requestAccess(forMediaType: cameraMediaType) { granted in
            DispatchQueue.main.sync {
                if granted {
                    // do something
                } else {
                    // do something else
                }
            }
        }
    }
}

首先在Info.plist中指定NSCameraUsageDescription键。然后检查AVAuthorizationStatus是否已授权，然后显示UIImagePickerController。会的。

Swift：使用AVFoundation

1. 将AVFoundation添加到Target-> Build Phases-> Link Binary with Libraries。
2. 在ViewController上导入AVFoundation。
3. 在Info.plist上，添加以下内容：

4. 在View Controller上：

@IBAction func cameraButtonClicked（sender：AnyObject）{

let authorizationStatus = AVCaptureDevice.authorizationStatusForMediaType(AVMediaTypeVideo)
print(authorizationStatus.rawValue)

if AVCaptureDevice.authorizationStatusForMediaType(AVMediaTypeVideo) ==  AVAuthorizationStatus.Authorized{
    self.openCameraAfterAccessGrantedByUser()
}
else
{
    print("No Access")

    dispatch_async(dispatch_get_main_queue()) { [unowned self] in
        AVCaptureDevice.requestAccessForMediaType(AVMediaTypeVideo, completionHandler: { (granted :Bool) -> Void in
            if granted == true
            {
                // User granted
                self.openCameraAfterAccessGrantedByUser()
            }
            else
            {
                // User Rejected
                  alertToEncourageCameraAccessWhenApplicationStarts()
            }
        });
    }
}


//Open camera

    func openCameraAfterAccessGrantedByUser()
    {
    if(UIImagePickerController .isSourceTypeAvailable(UIImagePickerControllerSourceType.Camera)){
        self.cameraAndGalleryPicker!.sourceType = UIImagePickerControllerSourceType.Camera
        cameraAndGalleryPicker?.delegate = self
        cameraAndGalleryPicker?.allowsEditing =  false
        cameraAndGalleryPicker!.cameraCaptureMode = .Photo
        cameraAndGalleryPicker!.modalPresentationStyle = .FullScreen
        presentViewController(self.cameraAndGalleryPicker!, animated: true, completion: nil)
    }
    else
    {

    }
}

//Show Camera Unavailable Alert

func alertToEncourageCameraAccessWhenApplicationStarts()
    {
        //Camera not available - Alert
        let cameraUnavailableAlertController = UIAlertController (title: "Camera Unavailable", message: "Please check to see if it is disconnected or in use by another application", preferredStyle: .Alert)

let settingsAction = UIAlertAction(title: "Settings", style: .Destructive) { (_) -> Void in
    let settingsUrl = NSURL(string:UIApplicationOpenSettingsURLString)
    if let url = settingsUrl {
        dispatch_async(dispatch_get_main_queue()) {
            UIApplication.sharedApplication().openURL(url)
        }

    }
}
let cancelAction = UIAlertAction(title: "Okay", style: .Default, handler: nil)
cameraUnavailableAlertController .addAction(settingsAction)
cameraUnavailableAlertController .addAction(cancelAction)
self.window?.rootViewController!.presentViewController(cameraUnavailableAlertController , animated: true, completion: nil)
}