为什么AVCaptureSession方法可以添加输出返回假?

Question

>我正在尝试构建一个相机应用程序，并且正在尝试在我的主视图控制器的viewDidLoad((中设置我的捕获会话。出于某种原因，每当我在手机上运行该应用程序时，AVCaptureSession 方法都可以添加输出被评估为假：

var captureSession: AVCaptureSession!
var photoOutput: AVCapturePhotoOutput!
var previewLayer : AVCaptureVideoPreviewLayer!
//MARK: Outlets
@IBOutlet weak var previewView: UIView!
override func viewDidLoad() {
super.viewDidLoad()
captureSession = AVCaptureSession()
captureSession.sessionPreset = AVCaptureSessionPresetPhoto
//Ask permission to camera
let device = AVCaptureDevice.defaultDevice(withDeviceType: .builtInWideAngleCamera, mediaType: AVMediaTypeVideo, position: .back)
AVCaptureDevice.requestAccess(forMediaType: AVMediaTypeVideo, completionHandler: { (granted: Bool) in
if granted {
print("granted")
//Set up session
if let input = try? AVCaptureDeviceInput(device: device) {
print("Input = device")
if (self.captureSession.canAddInput(input)) {
self.captureSession.addInput(input)
print("Input added to capture session")
if (self.captureSession.canAddOutput(self.photoOutput)) {
print("Output added to capture session")
self.captureSession.addOutput(self.photoOutput)
self.previewLayer = AVCaptureVideoPreviewLayer(session: self.captureSession)
self.previewLayer.frame = self.previewView.bounds
self.previewView.layer.addSublayer(self.previewLayer!)
self.captureSession.startRunning()
print("Session is running")
}
}
}
}
else {
print("Goodbye")
}
})
}

不幸的是，我只能让它打印到"输入添加到捕获会话"之前。任何建议都会有所帮助 - 谢谢！

Answer 1

您必须删除以前在会话中添加的输出。 你可以使用 for 循环。

for outputs in captureSession.outputs{ captureSession.removeOutput(outputs) }

然后尝试添加新的输出