swift – AVCaptureDevice.requestAccessForMediaType永远不会弹

我有一些问题询问用户有关相机的许可. authorizationStatus始终是NotDetermined.当我试图询问用户是否允许时,AVCaptureDevice.requestAccessForMediaType永远不会弹出一个对话框并且被授予总是返回false.我也找不到我的应用程序设置 – 隐私 – 相机.

任何人都可以帮助我吗？非常感谢

let availableCameraDevices = AVCaptureDevice.devicesWithMediaType(AVMediaTypeVideo)
    for device in availableCameraDevices{

        if (device.position == .Back){
            backCameraDevice = device
        }else{
            if (device.position == .Front){
                frontCameraDevice = device
            }
        }
    }

    let authorizationStatus = AVCaptureDevice.authorizationStatusForMediaType(AVMediaTypeVideo)
    switch authorizationStatus {
    case .NotDetermined:
        // permission dialog not yet presented,request authorization
        AVCaptureDevice.requestAccessForMediaType(AVMediaTypeVideo,completionHandler: { (granted:Bool) -> Void in
                if (granted == false) {
                    print(granted)
                }
                else {
                    print(granted)
                }
        })
    case .Authorized: break
        // go ahead
    case .Denied,.Restricted: break
        // the user explicitly denied camera usage or is not allowed to access the camera devices
    }