SwiftUI中FullScreenCover报错：已有有效定向事务令牌时请求新令牌

问题描述 #

使用SwiftUI的fullScreenCover修饰符时，在关闭当前视图并展示新视图的全屏过渡过程中，触发以下断言错误：

A new orientation transaction token is being requested while a valid one already exists

错误发生时，窗口与场景方向均为portrait，且存在一个原始方向同样为portrait的活跃定向事务令牌。

已尝试的无效方案：

• 显式设置windowOrientation与sceneOrientation
• 用NavigationStack包裹fullScreenCover的目标视图
• 展示新视图时调用presentationMode.wrappedValue.dismiss()关闭当前视图

错误日志 #

2023-06-10 21:37:10.137760+0300 SignEase[50521:19426350] [Assert] A new orientation transaction token is being requested while a valid one already exists. reason=Fullscreen transition (dismissing): fromVC=<__TtGC7SwiftUI29PresentationHostingControllerVS_7AnyView__: 0x13b80f200>; toVC=<__TtGC7SwiftUI29PresentationHostingControllerVS_7AnyView__: 0x13a8d7c00>;;; windowOrientation=portrait; sceneOrientation=portrait; existingTransaction=<__UIForcedOrientationTransactionToken: 0x280b814a0; state: active; originalOrientation: portrait (1)>

相关代码 #

import SwiftUI
import Firebase
import FirebaseCore
import FirebaseAuth


@available(iOS 16.0, *)
struct SignUp: View {
    @StateObject private var viewModal = SignViewData()
    @Environment(\.presentationMode) var presentationMode
    @State private var mainView = false
    @State private var SignInView = false
    
    var body: some View {
        ZStack {
            VStack(alignment: .leading){
                Text("Sign Up")
                    .font(.largeTitle)
                    .fontWeight(.bold)
                    .foregroundStyle(.linearGradient(colors: [.pink.opacity(0.6), .primary.opacity(0.5)], startPoint: .topLeading, endPoint: .bottomTrailing))
                    .padding(.leading,10)
                    .padding(.bottom,20)
                Section{
                    TextField("", text: $viewModal.text)
                        .textContentType(.emailAddress)
                        .keyboardType(.emailAddress)
                        .autocapitalization(.none)
                        .disableAutocorrection(true)
                        .placeholder(when: viewModal.text.isEmpty) {
                            Text("Email address")
                                .foregroundColor(.primary)
                                .blendMode(.overlay)
                        }
                        .customField(icon: "envelope.open.fill")
                    SecureField("", text: $viewModal.password)
                        .textContentType(.password)
                        .placeholder(when: viewModal.password.isEmpty) {
                            Text("Password")
                                .foregroundColor(.primary)
                                .blendMode(.overlay)
                        }
                        .customField(icon: "key.fill")
                    
                }
                .padding(.leading,10)
                .padding(.trailing,10)
                .padding(.bottom,10)
                
                Button {
                    Task{
                        do{
                            try await viewModal.signUp()
                            if viewModal.value == true{
                                DispatchQueue.main.async { // Add DispatchQueue.main.async block
                                    mainView.toggle()
                                }
                            }
                            return
                        }
                        catch {
                            print(error)
                        }
                    }
                } label: {
                    ButtonView(title: "Create Account")
                }
                .padding(.leading,10)
                .padding(.trailing,10)
                .fullScreenCover(isPresented: $mainView) {
// Any time i segue into this view i keep getting the error down below
                    NavigationStack{
                        RootView()
                    }
                }
                Divider()
                    .padding(5)
                    .padding(.leading,10)
                    .padding(.trailing,10)
                HStack{
                    Text("Already have an account?")
                        .font(.subheadline)
                        .foregroundStyle(.linearGradient(colors: [.pink.opacity(0.7), .primary.opacity(0.5)], startPoint: .topLeading, endPoint: .bottomTrailing))
                    Button {
                        SignInView.toggle()
                    } label: {
                        Text("Sign In")
                            .font(.subheadline)
                            .fontWeight(.semibold)
                            .foregroundColor(.black)
                    }
                }
                .fullScreenCover(isPresented:$SignInView){
                    NavigationStack{
                        SignIn()
                    }
                }
                .padding(.leading,20)
            }.padding(15)
                .frame(width: 400,height: 370)
                .background(.ultraThinMaterial, in: RoundedRectangle(cornerRadius: 30, style: .continuous))
                .shadow(color: Color("Shadow").opacity(0.3), radius: 10, x: 0, y: 10)
                .strokeStyle(cornerRadius: 30)
                .padding(20)
        }.background(
            Image("Background 4")
        )
    }
}

@available(iOS 16.0, *)
struct SignUp_Previews: PreviewProvider {
    static var previews: some View {
        SignUp()
    }
}

extension View {
    func placeholder<Content: View>(
        when shouldShow: Bool,
        alignment: Alignment = .leading,
        @ViewBuilder placeholder: () -> Content) -> some View {
            ZStack(alignment: alignment) {
                placeholder().opacity(shouldShow ? 1 : 0)
                self
            }
        }
}

解决方案尝试 #

1. 调整fullScreenCover的附加层级 #

将fullScreenCover从Button或HStack上移到最外层的容器（比如ZStack）上，避免视图层级嵌套导致的事务冲突：

ZStack {
    // 原有的VStack内容
}
.background(Image("Background 4"))
// 把fullScreenCover移到这里
.fullScreenCover(isPresented: $mainView) {
    NavigationStack{
        RootView()
    }
}
.fullScreenCover(isPresented:$SignInView){
    NavigationStack{
        SignIn()
    }
}

2. 延迟触发视图切换 #

在登录成功后，延迟一小段时间再切换mainView的状态，让当前视图的过渡状态先完成：

if viewModal.value == true{
    DispatchQueue.main.asyncAfter(deadline: .now() + 0.1) {
        mainView.toggle()
    }
}

3. 确保视图模型状态在主线程更新 #

检查SignViewData的signUp方法，确保value的更新操作在主线程执行：

func signUp() async throws {
    // 原有Firebase注册逻辑
    // ...
    // 更新状态时切到主线程
    DispatchQueue.main.async {
        self.value = true
    }
}

4. 临时禁用自动旋转（workaround） #

如果上述方法无效，可以在Info.plist中设置仅允许portrait方向，避免系统自动处理定向事务：

• 添加UISupportedInterfaceOrientations数组，只保留UIInterfaceOrientationPortrait
• 添加UISupportedInterfaceOrientations~ipad数组（如果适配iPad），同样只保留UIInterfaceOrientationPortrait

内容的提问来源于stack exchange，提问作者abdul lawal