SwiftUI 不会将状态更新为 @ObservedObject cameraViewModel 对象
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【中文标题】SwiftUI 不会将状态更新为 @ObservedObject cameraViewModel 对象【英文标题】：SwiftUI doesn't update state to @ObservedObject cameraViewModel object 【发布时间】：2020-11-10 14:12:22 【问题描述】：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()
【问题讨论】：
【参考方案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()
【讨论】：
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