SwiftUI 不会将状态更新为 @ObservedObject cameraViewModel 对象

Question

我是 SwiftUI 和手动相机功能的新手，我真的需要帮助。

所以我尝试构建一个 SwiftUI 相机视图，其中包含一个 UIKit 相机作为包装器，以通过 SwiftUI 选择器视图控制对焦镜头位置，显示在 fucus 值下方，并想尝试在 AVcaptureDevice.lensPosition 从 0 之间建立相关性到 1.0 和在焦点选择器视图中显示的专长。但现在，我只想在屏幕上显示那个墨角藻号。

问题是当我尝试通过协调器焦点观察更新焦点并将其设置为相机视图模型时，什么也没发生。请帮忙？？？？

代码如下：

import SwiftUI
import AVFoundation
import Combine

struct ContentView: View {
    
    @State private var didTapCapture = false
    @State private var focusLensPosition: Float = 0
    @ObservedObject var cameraViewModel = CameraViewModel(focusLensPosition: 0)
    
    var body: some View {
        
        VStack {
            ZStack {
                CameraPreviewRepresentable(didTapCapture: $didTapCapture, cameraViewModel: cameraViewModel)
                    .frame(maxWidth: .infinity, maxHeight: .infinity, alignment: .center)
                
                VStack {
                    FocusPicker(selectedFocus: $focusLensPosition)
                    
                    Text(String(cameraViewModel.focusLensPosition))
                        .foregroundColor(.red)
                        .font(.largeTitle)
                }
                .frame(maxWidth: .infinity, alignment: .leading)
            }
            .edgesIgnoringSafeArea(.all)
            
            Spacer()
            
            CaptureButton(didTapCapture: $didTapCapture)
                .frame(width: 100, height: 100, alignment: .center)
                .padding(.bottom, 20)
        }
        
        
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

struct CaptureButton: View {
    @Binding var didTapCapture : Bool
    
    var body: some View {
        Button {
            didTapCapture.toggle()
            
        } label: {
            Image(systemName: "photo")
                .font(.largeTitle)
                .padding(30)
                .background(Color.red)
                .foregroundColor(.white)
                .clipShape(Circle())
                .overlay(
                    Circle()
                        .stroke(Color.red)
                )
        }
    }
}

struct CameraPreviewRepresentable: UIViewControllerRepresentable {
    
    @Environment(\.presentationMode) var presentationMode
    @Binding var didTapCapture: Bool
    @ObservedObject var cameraViewModel: CameraViewModel
    
    let cameraController: CustomCameraController = CustomCameraController()
    
    func makeUIViewController(context: Context) -> CustomCameraController {
        cameraController.delegate = context.coordinator
        
        return cameraController
    }
    
    func updateUIViewController(_ cameraViewController: CustomCameraController, context: Context) {
        
        if (self.didTapCapture) {
            cameraViewController.didTapRecord()
        }
    }
    
    func makeCoordinator() -> Coordinator {
        Coordinator(self, cameraViewModel: cameraViewModel)
    }
    
    class Coordinator: NSObject, UINavigationControllerDelegate, AVCapturePhotoCaptureDelegate {
        let parent: CameraPreviewRepresentable
        var cameraViewModel: CameraViewModel
        
        var focusLensPositionObserver: NSKeyValueObservation?
        
        init(_ parent: CameraPreviewRepresentable, cameraViewModel: CameraViewModel) {
            self.parent = parent
            self.cameraViewModel = cameraViewModel
            super.init()
            
            focusLensPositionObserver = self.parent.cameraController.currentCamera?.observe(\.lensPosition, options: [.new]) { [weak self] camera, _ in

                print(Float(camera.lensPosition))
                
                //announcing changes via Publisher
                self?.cameraViewModel.focusLensPosition = camera.lensPosition
            }
        }
        
        deinit {
            focusLensPositionObserver = nil
        }
        
        func photoOutput(_ output: AVCapturePhotoOutput, didFinishProcessingPhoto photo: AVCapturePhoto, error: Error?) {
            
            parent.didTapCapture = false
            
            if let imageData = photo.fileDataRepresentation(), let image = UIImage(data: imageData) {
                UIImageWriteToSavedPhotosAlbum(image, nil, nil, nil)
            }
            
            parent.presentationMode.wrappedValue.dismiss()
        }
    }
}

class CameraViewModel: ObservableObject {
    @Published var focusLensPosition: Float = 0

    init(focusLensPosition: Float) {
        self.focusLensPosition = focusLensPosition
    }
}

class CustomCameraController: UIViewController {
    
    var image: UIImage?
    
    var captureSession = AVCaptureSession()
    var backCamera: AVCaptureDevice?
    var frontCamera: AVCaptureDevice?
    var currentCamera: AVCaptureDevice?
    var photoOutput: AVCapturePhotoOutput?
    var cameraPreviewLayer: AVCaptureVideoPreviewLayer?
    
    //DELEGATE
    var delegate: AVCapturePhotoCaptureDelegate?
    
    func showFocusLensPosition() -> Float {
//        guard let camera = currentCamera else { return 0 }
        
//        try! currentCamera!.lockForConfiguration()
//        currentCamera!.focusMode = .autoFocus
////        currentCamera!.setFocusModeLocked(lensPosition: currentCamera!.lensPosition, completionHandler: nil)
//        currentCamera!.unlockForConfiguration()
        
        return currentCamera!.lensPosition
    }
    
    func didTapRecord() {
        
        let settings = AVCapturePhotoSettings()
        photoOutput?.capturePhoto(with: settings, delegate: delegate!)
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        setup()
    }
    
    func setup() {
        
        setupCaptureSession()
        setupDevice()
        setupInputOutput()
        setupPreviewLayer()
        startRunningCaptureSession()
    }
    
    func setupCaptureSession() {
        captureSession.sessionPreset = .photo
    }
    
    func setupDevice() {
        let deviceDiscoverySession =
            AVCaptureDevice.DiscoverySession(deviceTypes: [.builtInWideAngleCamera],
                                                                      mediaType: .video,
                                                                      position: .unspecified)
        for device in deviceDiscoverySession.devices {
            
            switch device.position {
            case .front:
                self.frontCamera = device
            case .back:
                self.backCamera = device
            default:
                break
            }
        }
        
        self.currentCamera = self.backCamera
    }
    
    func setupInputOutput() {
        do {
            
            let captureDeviceInput = try AVCaptureDeviceInput(device: currentCamera!)
            captureSession.addInput(captureDeviceInput)
            photoOutput = AVCapturePhotoOutput()
            captureSession.addOutput(photoOutput!)
            
        } catch {
            print(error)
        }
        
    }
    
    func setupPreviewLayer() {
        
        self.cameraPreviewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
        self.cameraPreviewLayer?.videoGravity = AVLayerVideoGravity.resizeAspectFill
        
        let deviceOrientation = UIDevice.current.orientation
        cameraPreviewLayer?.connection?.videoOrientation = AVCaptureVideoOrientation(rawValue: deviceOrientation.rawValue)!
        
        self.cameraPreviewLayer?.frame = self.view.frame
//        view.transform = CGAffineTransform(scaleX: 0.5, y: 0.5)
        self.view.layer.insertSublayer(cameraPreviewLayer!, at: 0)
    }
    
    func startRunningCaptureSession() {
        captureSession.startRunning()
    }
}


struct FocusPicker: View {
    
    var feets = ["∞ ft", "30", "15", "10", "7", "5", "4", "3.5", "3", "2.5", "2", "1.5", "1", "0.5", "Auto"]
    
    @Binding var selectedFocus: Float
    
    var body: some View {
        
        Picker(selection: $selectedFocus, label: Text("")) {
            ForEach(0 ..< feets.count) {
                Text(feets[$0])
                    .foregroundColor(.white)
                    .font(.subheadline)
                    .fontWeight(.medium)
                
            }
            .animation(.none)
            .background(Color.clear)
            .pickerStyle(WheelPickerStyle())
        }
        .frame(width: 60, height: 200)
        .border(Color.gray, width: 5)
        .clipped()
    }
}

Answer 1

您提供的代码的问题是FocusPicker 视图中selectedFocus 的类型应该是整数而不是浮点数。因此，一种选择是将这种类型更改为 Integer，并找到一种方法将 AVCaptureDevice.lensPosition 表示为具有给定范围的 Integer。

第二个选项是用枚举替换 feets 数组。通过使枚举符合CustomStringConvertible 协议，您甚至可以提供适当的描述。请参阅下面的示例。

我已经删除了您的代码，因为您只是想在第一步中显示数字，因此代码更易于理解。

我的工作示例：

import SwiftUI
import Combine

struct ContentView: View {
    @ObservedObject var cameraViewModel = CameraViewModel(focusLensPosition: 0.5)
    
    var body: some View {
        VStack {
            ZStack {
                VStack {
                    FocusPicker(selectedFocus: $cameraViewModel.focusLensPosition)
                    
                    Text(String(self.cameraViewModel.focusLensPosition))
                        .foregroundColor(.red)
                        .font(.largeTitle)
                }
                .frame(maxWidth: .infinity, alignment: .leading)
            }
            .edgesIgnoringSafeArea(.all)
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

class CameraViewModel: ObservableObject {
    @Published var focusLensPosition: Float

    init(focusLensPosition: Float) {
        self.focusLensPosition = focusLensPosition
    }
}

enum Feets: Float, CustomStringConvertible, CaseIterable, Identifiable {
    case case1 = 0.0
    case case2 = 0.5
    case case3 = 1.0
    
    var id: Float { self.rawValue }
    var description: String {
        get {
            switch self {
            case .case1:
                return "∞ ft"
            case .case2:
                return "4"
            case .case3:
                return "Auto"
            }
        }
    }
}

struct FocusPicker: View {
    @Binding var selectedFocus: Float
    
    var body: some View {
        Picker(selection: $selectedFocus, label: Text("")) {
            ForEach(Feets.allCases) { feet in
                Text(feet.description)
            }
            .animation(.none)
            .background(Color.clear)
            .pickerStyle(WheelPickerStyle())
        }
        .frame(width: 60, height: 200)
        .border(Color.gray, width: 5)
        .clipped()
    }
}