SwiftUI视图嵌入UIHostingController后配色方案切换失效

问题根源：将SwiftUI视图嵌入UIHostingController时，UIKit的overrideUserInterfaceStyle设置优先级高于SwiftUI的preferredColorScheme，导致SwiftUI内部的配色切换无法同步到整个嵌入视图。

方案一：状态提升至UIKit层，双向绑定同步 #

步骤1：修改SwiftUI视图，使用@Binding传递状态 #

将原视图中的@State private var isDarkMode改为@Binding，让UIKit层可以共享并监听这个状态：

struct SettingsSUView: View {
  @State private var isPresented = false
  @Binding var isDarkMode: Bool // 改为Binding类型
  var body: some View {
    Button("Show Sheet") {
      isPresented = true
    }
    .sheet(isPresented: $isPresented) {
      List {
        Toggle("Dark Mode", isOn: $isDarkMode)
      }
      .preferredColorScheme(isDarkMode ? .dark : .light)
    }
  }
}

#Preview {
  SettingsSUView(isDarkMode: .constant(true))
}

步骤2：在UIKit控制器中管理状态并同步配色 #

在嵌入SwiftUI的UIViewController中，创建状态变量并绑定到SwiftUI视图，同时通过didSet监听状态变化，更新UIHostingController的overrideUserInterfaceStyle：

class YourParentVC: UIViewController {
  private var isDarkMode = true {
    didSet {
      // 状态变化时同步更新UIHostingController的配色
      contentHostingController.overrideUserInterfaceStyle = isDarkMode ? .dark : .light
    }
  }
  private lateinit var contentHostingController: UIHostingController<SettingsSUView>

  override func viewDidLoad() {
    super.viewDidLoad()
    setupHostingController()
  }

  private func setupHostingController() {
    // 将UIKit的状态绑定到SwiftUI视图
    let rootView = SettingsSUView(isDarkMode: $isDarkMode)
    contentHostingController = UIHostingController(rootView: rootView)
    // 初始化配色
    contentHostingController.overrideUserInterfaceStyle = isDarkMode ? .dark : .light
    
    addChild(contentHostingController)
    view.addSubview(contentHostingController.view)
    
    contentHostingController.view.snp.makeConstraints { make in
      make.edges.equalToSuperview()
    }
    
    contentHostingController.didMove(toParent: self)
  }
}

方案二：通过环境传递UIHostingController引用同步 #

如果不想将状态提升到UIKit层，可以通过自定义环境键传递UIHostingController的引用，在SwiftUI内部直接更新其配色设置。

步骤1：定义自定义环境键 #

struct HostingControllerKey: EnvironmentKey {
  static let defaultValue: UIHostingController<AnyView>? = nil
}

extension EnvironmentValues {
  var hostingController: UIHostingController<AnyView>? {
    get { self[HostingControllerKey.self] }
    set { self[HostingControllerKey.self] = newValue }
  }
}

步骤2：在UIKit中注入环境变量 #

创建UIHostingController时，将自身引用注入SwiftUI环境：

class YourParentVC: UIViewController {
  private lateinit var contentHostingController: UIHostingController<AnyView>

  override func viewDidLoad() {
    super.viewDidLoad()
    setupHostingController()
  }

  private func setupHostingController() {
    let rootView = SettingsSUView()
      .environment(\.hostingController, contentHostingController)
    
    contentHostingController = UIHostingController(rootView: rootView)
    addChild(contentHostingController)
    view.addSubview(contentHostingController.view)
    
    contentHostingController.view.snp.makeConstraints { make in
      make.edges.equalToSuperview()
    }
    
    contentHostingController.didMove(toParent: self)
  }
}

步骤3：在SwiftUI视图中监听状态变化更新配色 #

利用环境中的UIHostingController引用，在Toggle状态变化时同步更新其overrideUserInterfaceStyle：

struct SettingsSUView: View {
  @State private var isPresented = false
  @State private var isDarkMode = true
  @Environment(\.hostingController) private var hostingController
  
  var body: some View {
    Button("Show Sheet") {
      isPresented = true
    }
    .sheet(isPresented: $isPresented) {
      List {
        Toggle("Dark Mode", isOn: $isDarkMode)
          .onChange(of: isDarkMode) { newValue in
            hostingController?.overrideUserInterfaceStyle = newValue ? .dark : .light
          }
      }
      .preferredColorScheme(isDarkMode ? .dark : .light)
    }
    .onAppear {
      // 初始化时设置配色
      hostingController?.overrideUserInterfaceStyle = isDarkMode ? .dark : .light
    }
  }
}

内容的提问来源于stack exchange，提问作者Do Huynh Tuan Khai