Xcode Canvas 异步任务为何不执行，只在模拟器中工作？

Question

Xcode 的 canvas 异步任务await BottomCustomPopup().present()不执行，要在 simulator 中才执行

struct PartnerProfileView: View {
   @State private var showSheet: Bool = true
   let partnerName: String
   
   var body: some View {
      ZStack(alignment: .bottom) {
         Color("EFEFF4_0F2534")
         
         ScrollView(showsIndicators: false) {
            headerSection()
            
            infoSection()
               .padding(.bottom, 5)
            
            sectionTitle("Other Skills")
            
            skillsGrid()
            
            sectionTitle("···")
            
            dynamicsSection()
         }
         .frame(maxWidth: .infinity, maxHeight: .infinity)
         
         CustomTabBar()
      }
      .navigationBarHidden(true)
      .ignoresSafeArea(edges: .all)
      .onAppear {
         print("PartnerProfileView received")
         Task {
            await BottomCustomPopup().present()
         }
      }
      .onChange(of: showSheet) { oldState, newValue in
         print("oldState \(oldState)")
         print("newValue \(newValue)")
      }
   }
}

//@MainActor
struct BottomCustomPopup: BottomPopup {
    var body: some View {
        HStack(spacing: 0) {
            Text("Hello World")
            Spacer()
            Button(action: { Task { await dismissLastPopup() }}) { Text("Dismiss") }
        }
        .padding(.vertical, 20)
        .padding(.leading, 24)
        .padding(.trailing, 16)
    }
}

Answer 1

使用条件编译来区分 Canvas 预览和实际运行环境。例如，你可以在 onAppear 中添加一个条件检查，确保异步任务只在非 Canvas 环境中执行：

.onAppear {
    print("PartnerProfileView received")
    #if !targetEnvironment(simulator)
    Task {
        await BottomCustomPopup().present()
    }
    #endif
}

或者

1. 添加环境变量来识别是否在预览环境中
2. 在预览环境中使用同步方式显示弹窗
3. 在实际运行环境中保持原有的异步调用方式

// 添加这个预览 Provider
struct PreviewContextProvider: PreviewProvider {
    static var previews: some View {
        PartnerProfileView(partnerName: "Test Partner")
            .previewLayout(.sizeThatFits)
            // 关键是添加这个 modifier
            .environment(\.isPreview, true)
    }
}

// 添加这个环境值 key
struct IsPreviewKey: EnvironmentKey {
    static let defaultValue: Bool = false
}

extension EnvironmentValues {
    var isPreview: Bool {
        get { self[IsPreviewKey.self] }
        set { self[IsPreviewKey.self] = newValue }
    }
}

// 修改原来的 PartnerProfileView
struct PartnerProfileView: View {
    @State private var showSheet: Bool = true
    @Environment(\.isPreview) private var isPreview
    let partnerName: String
    
    var body: some View {
        ZStack(alignment: .bottom) {
            // ... 其他代码保持不变 ...
        }
        .navigationBarHidden(true)
        .ignoresSafeArea(edges: .all)
        .onAppear {
            print("PartnerProfileView received")
            if isPreview {
                // 在预览环境中直接显示弹窗
                BottomCustomPopup().showInPreview()
            } else {
                // 在真实环境中使用异步方式
                Task {
                    await BottomCustomPopup().present()
                }
            }
        }
        .onChange(of: showSheet) { oldState, newValue in
            print("oldState \(oldState)")
            print("newValue \(newValue)")
        }
    }
}

// 扩展 BottomCustomPopup 添加预览支持
extension BottomCustomPopup {
    func showInPreview() {
        // 实现预览环境下的直接显示逻辑
        // 这里可以根据你的 BottomPopup 协议具体实现来调整
    }
}