如何将UIViewRepresentable与AVSampleBufferDisplayLayer一起传递给SwiftUI

当视图加载到设备上时,我只有一个黑屏。使用Storyboard实例和UIViewController时,我有非常相似的代码,但我需要摆脱它,因为我使用的是visionOS,我想将其抽象为使用RealityKit和VideoPlayerLayer,但为了原型设计和迭代其他任务,我希望这个AVSampleBufferDisplayLayer能够工作……最终我必须将AVSampleBufferVideoRenderer传递给VideoPlayerLayer,这样实现就可以帮助我深入了解RealityKit渲染。

这是代码,为了便于调试和提问,我将所有内容都塞进了一个文件中。

非常感谢。

struct MirrorView: View {
    var body: some View {
        VStack {
            LayerView()
        }
    }
}

struct LayerView: UIViewRepresentable {
    func makeUIView(context: Context) -> UIView {
        print("LayerUIView is being created")
        return LayerUIView()
            
    }
    
    func updateUIView(_ uiView: UIView, context: UIViewRepresentableContext<LayerView>) {
        print("LayerUIView is being updated")
    }
}

class LayerUIView: UIView {
    
    private let networking = Networking()
    private let displayLayer = AVSampleBufferDisplayLayer()
    private var subscriptions = Set<AnyCancellable>()
    private var sampleBufferTask: Task<Void, Never>?
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        print("LayerUIView initialized")
        setupVideoLayer()
        setupNetworking()
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func layoutSubviews() {
        super.layoutSubviews()
        layer.frame = bounds
    }
    
    private func setupVideoLayer() {
        
        displayLayer.frame = bounds
        displayLayer.videoGravity = .resizeAspect
        
        layer.addSublayer(displayLayer)
        NotificationCenter.default.addObserver(
                self,
                selector: #selector(handleFailedToDecodeNotification(_:)),
                name: .AVSampleBufferDisplayLayerFailedToDecode,
                object: displayLayer
            )
        }

        @objc private func handleFailedToDecodeNotification(_ notification: Notification) {
            if let error = notification.userInfo?[AVSampleBufferDisplayLayerFailedToDecodeNotificationErrorKey] {
                print("Failed to decode sample buffer. Error: \(error)")
            } else {
                print("Failed to decode sample buffer. No error information available.")
            }
        }
    
    private func setupNetworking() {
        networking.startAdvertising()
        print("Networking is connected: \(networking.isConnected)")
        startSampleBufferTask()
    }

    // MARK: - Task Management
    private func startSampleBufferTask() {
        
        sampleBufferTask = Task {
            for await sampleBuffer in networking.sampleBuffers {
                let formatDescription = CMSampleBufferGetFormatDescription(sampleBuffer)
                print("Format Description: \(String(describing: formatDescription))")

                let presentationTimeStamp = CMSampleBufferGetPresentationTimeStamp(sampleBuffer)
                print("Presentation Timestamp: \(presentationTimeStamp)")

                let duration = CMSampleBufferGetDuration(sampleBuffer)
                print("Duration: \(duration)")
                
                DispatchQueue.main.async {
                    self.displayLayer.sampleBufferRenderer.enqueue(sampleBuffer)
                }
            }
        }
    }

    private func stopSampleBufferTask() {
        sampleBufferTask?.cancel()
        sampleBufferTask = nil
    }
}

#Preview {
    MirrorView()
}

我创建了一个UIKit版本,并成功地将其作为iOS设备加载到AVP中。

下面是运行该代码的ViewController:

class ViewController: UIViewController { //, VideoDecoderAnnexBAdaptorDelegate {
    
    // MARK: - Properties
    private let networking = Networking()
    private let displayLayer = AVSampleBufferDisplayLayer()
    private var subscriptions = Set<AnyCancellable>()
    private var sampleBufferTask: Task<Void, Never>?
    
    // MARK: - Lifecycle
    override func viewDidLoad() {
        super.viewDidLoad()
        
        setupVideoLayer()
        setupNetworking()
    }
    
    override var supportedInterfaceOrientations: UIInterfaceOrientationMask {
        return .allButUpsideDown
    }

    override var shouldAutorotate: Bool {
        return true
    }
    
    override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
        super.viewWillTransition(to: size, with: coordinator)
        
        coordinator.animate(alongsideTransition: { _ in
            // Adjust layout for new orientation
            self.displayLayer.frame = self.view.bounds
        }, completion: nil)
    }
    
    // MARK: - Setup Methods
    private func setupVideoLayer() {
        displayLayer.frame = view.bounds
        displayLayer.videoGravity = .resizeAspect
        displayLayer.backgroundColor = UIColor.black.cgColor
        view.layer.addSublayer(displayLayer)
        NotificationCenter.default.addObserver(
                self,
                selector: #selector(handleFailedToDecodeNotification(_:)),
                name: .AVSampleBufferDisplayLayerFailedToDecode,
                object: displayLayer
            )
        }

        @objc private func handleFailedToDecodeNotification(_ notification: Notification) {
            if let error = notification.userInfo?[AVSampleBufferDisplayLayerFailedToDecodeNotificationErrorKey] {
                print("Failed to decode sample buffer. Error: \(error)")
            } else {
                print("Failed to decode sample buffer. No error information available.")
            }
        }
    
    private func setupNetworking() {
        networking.startAdvertising()
        print("Networking is connected: \(networking.isConnected)")
        startSampleBufferTask()
    }

    // MARK: - Task Management
    private func startSampleBufferTask() {
        
        sampleBufferTask = Task {
            for await sampleBuffer in networking.sampleBuffers {
                let formatDescription = CMSampleBufferGetFormatDescription(sampleBuffer)
                print("Format Description: \(String(describing: formatDescription))")

                let presentationTimeStamp = CMSampleBufferGetPresentationTimeStamp(sampleBuffer)
                print("Presentation Timestamp: \(presentationTimeStamp)")

                let duration = CMSampleBufferGetDuration(sampleBuffer)
                print("Duration: \(duration)")
                
                DispatchQueue.main.async {
                    self.displayLayer.sampleBufferRenderer.enqueue(sampleBuffer)
                }
            }
        }
    }

    private func stopSampleBufferTask() {
        sampleBufferTask?.cancel()
        sampleBufferTask = nil
    }
}