Ios 添加AVCaptureDeviceInput时AVCaptureSession崩溃

我在Crashlytics上看到了一个奇怪的崩溃，当时我正在设置一个摄像头会话。 stacktrace显示崩溃发生在方法addInput

func setupCamSession(){
    self.captureSession = AVCaptureSession()
    self.cameraView.setSession(self.captureSession)
    self.sessionQueue = dispatch_queue_create("com.myapp.camera_queue", DISPATCH_QUEUE_SERIAL)
    self.setupResult = .Success
    switch AVCaptureDevice.authorizationStatusForMediaType(AVMediaTypeVideo){
    case .Authorized:
        break //already we set it to success
    case .NotDetermined:
        // The user has not yet been presented with the option to grant video access.
        // We suspend the session queue to delay session setup until the access request has completed 
        dispatch_suspend(self.sessionQueue)
        AVCaptureDevice.requestAccessForMediaType(AVMediaTypeVideo, completionHandler: { (granted) -> Void in
            if ( !granted ) {
                self.setupResult = .CameraNotAuthorized
            }
            dispatch_resume(self.sessionQueue)
        })
    default:
        self.setupResult = .CameraNotAuthorized
    }

    dispatch_async(self.sessionQueue){
        if self.setupResult != .Success{
            return
        }
        //link input to captureSession
        guard let videoDevice = self.deviceWithMediaType(AVMediaTypeVideo, position: AVCaptureDevicePosition.Back) else{
            AppLog("Video Device Unavailable")
            self.setupResult = .SessionConfigurationFailed
            return
        }
        var videoDeviceInput: AVCaptureDeviceInput!
        do {
            videoDeviceInput = try AVCaptureDeviceInput(device: videoDevice)
        }catch {
            AppLog("Could not create video device input")
        }

        /////////////////////////////////////////////////////
        self.captureSession.beginConfiguration()

        if self.captureSession.canAddInput(videoDeviceInput){
            self.captureSession.addInput(videoDeviceInput)
            self.videoDeviceInput = videoDeviceInput
            self.videoDevice = videoDevice
            dispatch_async(dispatch_get_main_queue()){
                //update the cameraView layer on the main thread
                let previewLayer : AVCaptureVideoPreviewLayer = self.cameraView.layer as! AVCaptureVideoPreviewLayer
                previewLayer.connection.videoOrientation = AVCaptureVideoOrientation(ui:UIApplication.sharedApplication().statusBarOrientation)
            }
        }else{
            AppLog("Could not add video device input to the session")
            self.setupResult = .SessionConfigurationFailed
        }

        //link output to captureSession
        let stillImageOutput = AVCaptureStillImageOutput()
        if self.captureSession.canAddOutput(stillImageOutput){
            self.captureSession.addOutput(stillImageOutput)
            self.stillImageOutput = stillImageOutput
            stillImageOutput.outputSettings = [AVVideoCodecKey : AVVideoCodecJPEG]
        }else{
            AppLog("Could not add still image output to the session")
            self.setupResult = .SessionConfigurationFailed
        }

        self.captureSession.commitConfiguration()
        /////////////////////////////////////////////////////
    }
}

func runSession(){
    dispatch_async(self.sessionQueue){
        switch self.setupResult!{
        case .Success:
            self.videoDeviceInput!.device.addObserver(self, forKeyPath: "adjustingFocus", options: NSKeyValueObservingOptions.New, context: nil)
            self.captureSession.addObserver(self, forKeyPath: "running", options: [.New], context: &SessionRunningContext)
            self.captureSession.startRunning()
            self.captureSessionRunning = self.captureSession.running
            if !self.captureSessionRunning {
                self.captureSession.removeObserver(self, forKeyPath: "running", context: &SessionRunningContext)
                self.videoDeviceInput?.device?.removeObserver(self, forKeyPath: "adjustingFocus", context: nil)
            }
       default:
       //Handle errors.
       }
  }
func stopCaptureSession(){
    dispatch_async(self.sessionQueue){
        if self.setupResult == .Success{
            if self.captureSessionRunning{
                self.captureSession.stopRunning()
                self.videoDeviceInput?.device?.removeObserver(self, forKeyPath: "adjustingFocus", context: nil)
                self.captureSession.removeObserver(self, forKeyPath: "running", context: &SessionRunningContext)
            }
            self.captureSessionRunning = false
        }
    }
}

setupCamSession在viewDidLoad中调用，runSession在ViewWillDisplay中出现，我在ViewWillDemouse中还有一个stopSession方法。与摄像头会话相关的所有内容都在后台串行队列中调度

崩溃不会100%发生，我无法在我使用的设备上重现崩溃。 谢谢

---

确保您正在删除Denit上的观察者。我在返回摄像头捕获屏幕时看到了这种情况，我没有移除调整焦距的观测者。一旦我在Denit中删除了它，一切都很好

也有同样的问题。在Info.plist文件中添加了

隐私-摄像头使用说明

的使用说明后，问题得以解决。此答案包含有关如何设置描述的提示：

---

将其移动到ViewWillDisplay或ViewDidAppear为什么？我更喜欢将其保存在viewDidLoad（）中。事实上，主屏幕上有摄像头视图，我们在主屏幕上多次按下和弹出视图控制器。因此，VIEWWILLISPEND将被多次调用，并且每次都将再次设置相机会话。目前，它只是在运行摄像头会话。我的灵感来自。他们在viewDidLoad（）中设置输入崩溃报告中还有其他信息吗？就像“在参数寄存器中找到选择器名称”？不。这是我在报告中的全部内容。我编辑了我的问题并添加了stopCaptureSession（）方法。此方法是移除用于调整焦点的观察者。日志上说观察员已经被移除，然后Denit被调用。是否有可能videoDeviceInput.device以某种方式变为零？如果发生这种情况，

self.videoDeviceInput？.device？.removeObserver（self，forKeyPath:“adjustingFocus”，context:nil）

将不会被调用。非常感谢。这正是我的问题。