AVFoundation预览未显示

Question

Swift3 iOS10应用。我在故事板框架中放了一个SCNView。我在其上面放了一个UIView（Bring to Front）并调整大小，使其仅填充屏幕中心的一部分。

在我的viewDidLoad我使用AVFoundation查找相机，构建会话，添加输入，进行预览，然后将该预览添加到UIView的图层。

我得到一个白色矩形而不是预览：

我认为我错过了某个地方......

// 3D scene and vars
@IBOutlet var sceneView: SCNView!
var camera: SCNNode!
var sphere: SCNNode!

// camera scene and vars
@IBOutlet var cameraView: UIView!
var cameraSession: AVCaptureSession = AVCaptureSession()
var cameraDevice : AVCaptureDevice!
var cameraInput : AVCaptureDeviceInput!
var cameraLayer: AVCaptureVideoPreviewLayer!

override func viewDidLoad() {
    ... 3D setup here ...

    cameraDevice = AVCaptureDevice.defaultDevice(withDeviceType: .builtInWideAngleCamera, mediaType: AVMediaTypeVideo, position: .back)
    do {
        let possibleCameraInput: AnyObject? = try AVCaptureDeviceInput(device: cameraDevice)
        if let anInput = possibleCameraInput as? AVCaptureDeviceInput {
            if cameraSession.canAddInput(anInput) {
                cameraSession.addInput(anInput)
            }
        }
    } catch _ {
        //TODO handle this error
    }
    // add the preview layer to our imageview
    if cameraSession.inputs.count > 0 {
        cameraLayer = AVCaptureVideoPreviewLayer(session: cameraSession) as AVCaptureVideoPreviewLayer
        cameraView.layer.addSublayer(cameraLayer)
    }
    cameraSession.startRunning()

Answer 1

好吧，这确实只是一些缺失的步骤。你必须手动设置masksToBounds，videoGravity和框架或没有任何反应（错误？坏API？）...

        let viewLayer = cameraView.layer
        viewLayer.masksToBounds = true
        cameraView.backgroundColor = UIColor.clear
        cameraLayer = AVCaptureVideoPreviewLayer(session: cameraSession) as AVCaptureVideoPreviewLayer
        cameraLayer.videoGravity = AVLayerVideoGravityResizeAspectFill
        cameraLayer.frame = cameraView.frame
        cameraView.layer.addSublayer(cameraLayer)

启动并运行！