Swift 4 Capture Photo，photoOutput返回nil

Question

目前，我有两个不同的视图控制器和一个在它们之间切换的按钮。 我希望在每张照片上都能拍摄到设备输入的照片。

目前，我可以拍摄后置摄像头的照片以进行处理，并且效果很好，但是当我尝试在第二个视图的另一个控制器中编写相同的代码时，照片输出将返回nil，但是当我记录每个设备时，仍然显示前后摄像头。

我是新手，不知道为什么会这样。

ViewController类，viewDidLoad和变量：

class AddUserController: UIViewController , AVCaptureVideoDataOutputSampleBufferDelegate , UITextFieldDelegate{

   //variable for captureing video feed
   var captureSessionFront = AVCaptureSession()
   //variable for rendering camera to the view
   var videoPreviewLayer: AVCaptureVideoPreviewLayer?

   var frontCamera: AVCaptureDevice?
   var backCamera: AVCaptureDevice?
   var currentCamera2: AVCaptureDevice?
   var PhotoOutputFront: AVCapturePhotoOutput?
   var cameraPreviewLayer2: AVCaptureVideoPreviewLayer?

   var tempImage: UIImage?

   var tempstring: String?

   private var maskLayer = [CAShapeLayer]()



   @IBOutlet weak var textField: UITextField!

   //button action to save the user to the collection
   @IBAction func saveFaceBtn(_ sender: Any) {
       let settings = AVCapturePhotoSettings()
       PhotoOutputFront?.capturePhoto(with: settings, delegate: self)
       //print(PhotoOutputFront!)
   }

   override func viewDidLoad() {
       super.viewDidLoad()
       // Do any additional setup after loading the view, typically from a nib.

       //hide keyboard
       self.textField.delegate = self

       //video capture functions
       setupCaptureSession()
       setupDevice()
       setupInputOutput()
       setupPreview()
       startRunningCaptureSession()

职能：

func setupCaptureSession() {
       captureSessionFront.sessionPreset = AVCaptureSession.Preset.photo
   }
func setupDevice() {

       //discover devices
       let deviceDiscoverySession = AVCaptureDevice.DiscoverySession(
           deviceTypes: [AVCaptureDevice.DeviceType.builtInWideAngleCamera],
           mediaType: AVMediaType.video,
           position: AVCaptureDevice.Position.unspecified)

       //find devices and check if frint or back cameras discovered
       let devices = deviceDiscoverySession.devices

       for device in devices{
           print(device)
           if device.position == AVCaptureDevice.Position.front{
               frontCamera = device

           } else if device.position == AVCaptureDevice.Position.back{
               backCamera = device
           }
       }

       currentCamera2 = frontCamera

   }

   func setupInputOutput() {

       do
       {

           let captureDeviceInput2 = try AVCaptureDeviceInput(device: currentCamera2!)

           captureSessionFront.addInput(captureDeviceInput2)
           PhotoOutputFront?.setPreparedPhotoSettingsArray([AVCapturePhotoSettings(format: [AVVideoCodecKey: AVVideoCodecType.jpeg])], completionHandler: nil)
           print(PhotoOutputFront)
       }
       catch
       {
           print(error)
       }
   }

   func setupPreview() {
       cameraPreviewLayer2 = AVCaptureVideoPreviewLayer(session: captureSessionFront)
       cameraPreviewLayer2?.videoGravity = AVLayerVideoGravity.resizeAspectFill
       cameraPreviewLayer2?.connection?.videoOrientation = AVCaptureVideoOrientation.portrait
       cameraPreviewLayer2?.frame = self.view.frame
       self.view.layer.insertSublayer(cameraPreviewLayer2!, at: 0)
   }

   func startRunningCaptureSession() {
       captureSessionFront.startRunning()
   }

扩展名，用于保存捕获的照片：

extension AddUserController: AVCapturePhotoCaptureDelegate {

   func photoOutput(_ output: AVCapturePhotoOutput, didFinishProcessingPhoto photo: AVCapturePhoto, error: Error?) {
       print("before if let")
       if let imageData = photo.fileDataRepresentation(){
           tempImage = UIImage(data: imageData)
           print(tempImage!)

           //check to see if name is empty
           let tempstring = self.textField.text
           if(tempstring != nil || tempstring != ""){

               print(tempstring!)
               //addPhotoToCollection()
           }


       }
   }

}

必须设置输入输出，但是我不确定哪里出了问题，因为此代码适用于我的主视图控制器中的后置摄像头。 我认为这与该功能有关，因为在我的其他控制器“ PhotoOutput”中不会返回nil。 此处“ PhotoOutputFront”返回nil。

view    func setupInputOutput() {

       do
       {

           let captureDeviceInput2 = try AVCaptureDeviceInput(device: currentCamera2!)

           captureSessionFront.addInput(captureDeviceInput2)
           PhotoOutputFront?.setPreparedPhotoSettingsArray([AVCapturePhotoSettings(format: [AVVideoCodecKey: AVVideoCodecType.jpeg])], completionHandler: nil)
           print(PhotoOutputFront)
       }
       catch
       {
           print(error)
       }
   }

任何帮助将不胜感激。 提前致谢！

Answer 1

问题是我没有将捕获设备添加为捕获会话的输入，也没有添加捕获会话的输出。

希望这对使用捕获设备遇到麻烦的其他人有所帮助。 :)

func setupInputOutput() {

       do
       {

           let captureDeviceInput2 = try AVCaptureDeviceInput(device: currentCamera2!)

           captureSessionFront.addInput(captureDeviceInput2)
           PhotoOutputFront = AVCapturePhotoOutput()
           PhotoOutputFront?.setPreparedPhotoSettingsArray([AVCapturePhotoSettings(format: [AVVideoCodecKey: AVVideoCodecType.jpeg])], completionHandler: nil)
           captureSessionFront.addOutput(PhotoOutputFront!)
       }
       catch
       {
           print(error)
       }
   }

Answer 2

添加输出：

if captureSessionFront?.canAddOutput(PhotoOutputFront) {
  let settings = AVCapturePhotoSettings()
  let previewPixelType = 
  settings.__availablePreviewPhotoPixelFormatTypes.first!
  let previewFormat = [kCVPixelBufferPixelFormatTypeKey as String: previewPixelType,
                   kCVPixelBufferWidthKey as String: 160,
                   kCVPixelBufferHeightKey as String: 160]
  settings.previewPhotoFormat = previewFormat
  settings.isHighResolutionPhotoEnabled = 
  PhotoOutputFront.isHighResolutionCaptureEnabled
  PhotoOutputFront.setPreparedPhotoSettingsArray([settings], completionHandler: { (finished, anError) in
    guard let error = anError else { return }
    debugPrint("Failed to set photo settings with: \(error.localizedDescription)")
  })
  captureSessionFront.addOutput(PhotoOutputFront)
}

在添加输出之前，请添加输入：

if captureSessionFront.canAddInput(captureDeviceInput2) {
    captureSessionFront.addInput(captureDeviceInput2)
}