Xcode 环境使用NavigationLink时对象刷新/移交问题

我目前正在macOS Catalina上使用XCode 11.5中的Swift/SwiftUI为watchOS 6（独立应用程序）开发一个应用程序

在用户可以使用我的应用程序之前，需要进行配置过程。由于配置过程由几个不同的视图组成，这些视图一个接一个地显示，因此我使用导航链接实现了这一点

配置过程完成后，用户应单击按钮返回“主”应用程序（主视图）。对于控制处于同一层次级别的视图，我的计划是使用EnvironmentObject（据我所知，一个EnvironmentObject一旦被注入，就会被交给子视图，子视图可以使用EnvironmentObject）与控制视图显示的“控制视图”相结合。因此，我遵循了教程：

这是我的代码：

ContentView.swift

struct ContentView: View {
    var body: some View {
        ContentViewManager().environmentObject(AppStateControl())        
    }
}

struct ContentViewManager: View {
    @EnvironmentObject var appStateControl: AppStateControl
    
    var body: some View {
        VStack {
            if(appStateControl.callView == "AppConfig") {
                AppConfig()
            }
            if(appStateControl.callView == "AppMain") {
                AppMain()
            }
        }
    }
}

class AppStateControl: ObservableObject {
    @Published var callView: String = "AppConfig"
}

struct AppConfig: View {
    @EnvironmentObject var appStateControl: AppStateControl
    var body: some View {
        VStack {
            Text("App Config Main")
            NavigationLink(destination: DetailView1().environmentObject(appStateControl)) {
                Text("Show Detail View 1")
            }
        }
    }
}

struct DetailView1: View {
    @EnvironmentObject var appStateControl: AppStateControl
    var body: some View {
        VStack {
            Text("App Config Detail View 1")
            NavigationLink(destination: DetailView2().environmentObject(appStateControl)) {
                Text("Show Detail View 2")
            }
        }
    }
}

struct DetailView2: View {
    @EnvironmentObject var appStateControl: AppStateControl
    var body: some View {
        VStack {
            Text("App Config Detail View 2")
            Button(action: {
                self.appStateControl.callView = "AppMain"
            }) {
             Text("Go to main App")
            }
        }
    }
}

struct AppMain: View {
    var body: some View {
        Text("Main App")
    }
}

AppStateControl.swift

struct ContentView: View {
    var body: some View {
        ContentViewManager().environmentObject(AppStateControl())        
    }
}

struct ContentViewManager: View {
    @EnvironmentObject var appStateControl: AppStateControl
    
    var body: some View {
        VStack {
            if(appStateControl.callView == "AppConfig") {
                AppConfig()
            }
            if(appStateControl.callView == "AppMain") {
                AppMain()
            }
        }
    }
}

class AppStateControl: ObservableObject {
    @Published var callView: String = "AppConfig"
}

struct AppConfig: View {
    @EnvironmentObject var appStateControl: AppStateControl
    var body: some View {
        VStack {
            Text("App Config Main")
            NavigationLink(destination: DetailView1().environmentObject(appStateControl)) {
                Text("Show Detail View 1")
            }
        }
    }
}

struct DetailView1: View {
    @EnvironmentObject var appStateControl: AppStateControl
    var body: some View {
        VStack {
            Text("App Config Detail View 1")
            NavigationLink(destination: DetailView2().environmentObject(appStateControl)) {
                Text("Show Detail View 2")
            }
        }
    }
}

struct DetailView2: View {
    @EnvironmentObject var appStateControl: AppStateControl
    var body: some View {
        VStack {
            Text("App Config Detail View 2")
            Button(action: {
                self.appStateControl.callView = "AppMain"
            }) {
             Text("Go to main App")
            }
        }
    }
}

struct AppMain: View {
    var body: some View {
        Text("Main App")
    }
}

AppConfig.swift

struct ContentView: View {
    var body: some View {
        ContentViewManager().environmentObject(AppStateControl())        
    }
}

struct ContentViewManager: View {
    @EnvironmentObject var appStateControl: AppStateControl
    
    var body: some View {
        VStack {
            if(appStateControl.callView == "AppConfig") {
                AppConfig()
            }
            if(appStateControl.callView == "AppMain") {
                AppMain()
            }
        }
    }
}

class AppStateControl: ObservableObject {
    @Published var callView: String = "AppConfig"
}

struct AppConfig: View {
    @EnvironmentObject var appStateControl: AppStateControl
    var body: some View {
        VStack {
            Text("App Config Main")
            NavigationLink(destination: DetailView1().environmentObject(appStateControl)) {
                Text("Show Detail View 1")
            }
        }
    }
}

struct DetailView1: View {
    @EnvironmentObject var appStateControl: AppStateControl
    var body: some View {
        VStack {
            Text("App Config Detail View 1")
            NavigationLink(destination: DetailView2().environmentObject(appStateControl)) {
                Text("Show Detail View 2")
            }
        }
    }
}

struct DetailView2: View {
    @EnvironmentObject var appStateControl: AppStateControl
    var body: some View {
        VStack {
            Text("App Config Detail View 2")
            Button(action: {
                self.appStateControl.callView = "AppMain"
            }) {
             Text("Go to main App")
            }
        }
    }
}

struct AppMain: View {
    var body: some View {
        Text("Main App")
    }
}

AppMain.swift

struct ContentView: View {
    var body: some View {
        ContentViewManager().environmentObject(AppStateControl())        
    }
}

struct ContentViewManager: View {
    @EnvironmentObject var appStateControl: AppStateControl
    
    var body: some View {
        VStack {
            if(appStateControl.callView == "AppConfig") {
                AppConfig()
            }
            if(appStateControl.callView == "AppMain") {
                AppMain()
            }
        }
    }
}

class AppStateControl: ObservableObject {
    @Published var callView: String = "AppConfig"
}

struct AppConfig: View {
    @EnvironmentObject var appStateControl: AppStateControl
    var body: some View {
        VStack {
            Text("App Config Main")
            NavigationLink(destination: DetailView1().environmentObject(appStateControl)) {
                Text("Show Detail View 1")
            }
        }
    }
}

struct DetailView1: View {
    @EnvironmentObject var appStateControl: AppStateControl
    var body: some View {
        VStack {
            Text("App Config Detail View 1")
            NavigationLink(destination: DetailView2().environmentObject(appStateControl)) {
                Text("Show Detail View 2")
            }
        }
    }
}

struct DetailView2: View {
    @EnvironmentObject var appStateControl: AppStateControl
    var body: some View {
        VStack {
            Text("App Config Detail View 2")
            Button(action: {
                self.appStateControl.callView = "AppMain"
            }) {
             Text("Go to main App")
            }
        }
    }
}

struct AppMain: View {
    var body: some View {
        Text("Main App")
    }
}

在以前版本的代码中（没有始终移交EnvironmentObject），我遇到了一个运行时错误（“线程1：致命错误：未找到AppStateControl类型的ObservableObject。AppStateControl的View.EnvironmentObject（:）可能作为此视图的祖先丢失。”），这是由AppConfig.swift中的第41行引起的。在互联网上，我读到这可能是NavigationLink的一个bug（请参阅：，）。因此，建议显式地将EnvironmentObject传递到NavigationLink的目标（上面的实现）。不幸的是，这也不起作用，而是点击“DetailView2”中的“Go to main App”（转到主应用程序）按钮将导致视图“DetailView1”而不是“AppMain”

有没有办法解决这个问题？在我看来，在通过导航链接调用的视图中更改EnvironmentObject似乎不会刷新视图（正确）

---

提前感谢。

解决方案之一是创建一个变量，控制是否显示导航堆栈

class AppStateControl: ObservableObject {
    ...
    @Published var isDetailActive = false // <- add this
}

所有其他链接：

NavigationLink(destination: DetailView2().environmentObject(appStateControl)) {
    Text("Show Detail View 2")
}
.isDetailLink(false)

然后只需将

isDetailActive

设置为

false

即可弹出所有导航链接并返回主视图：

Button(action: {
    self.appStateControl.callView = "AppMain"
    self.appStateControl.isDetailActive = false // <- add this
}) {
    Text("Go to main App")
}

按钮（操作：{
self.appStateControl.callView=“AppMain”
self.appStateControl.isDetailActive=false/解决方案之一是创建一个变量来控制是否显示导航堆栈

class AppStateControl: ObservableObject {
    ...
    @Published var isDetailActive = false // <- add this
}

所有其他链接：

NavigationLink(destination: DetailView2().environmentObject(appStateControl)) {
    Text("Show Detail View 2")
}
.isDetailLink(false)

然后只需将
isDetailActive
设置为
false
即可弹出所有导航链接并返回主视图：

Button(action: {
    self.appStateControl.callView = "AppMain"
    self.appStateControl.isDetailActive = false // <- add this
}) {
    Text("Go to main App")
}

按钮（操作：{
self.appStateControl.callView=“AppMain”
self.appStateControl.isDetailActive=false//感谢您的快速回复！我刚刚实现了解决方案，但是，应用程序的行为与以前相同。不幸的是，.isdetailink（false）在watchOS中不可用。关于如何解决此问题或为什么我的应用程序会这样做，还有其他想法吗？@JPF哦，我明白了，我的错。你可以看到这个问题，我认为这也解释了如何在watchOS上工作。想法是一样的-你需要回到导航堆栈的根目录，以显示
AppMain
，而不是
>AppConfig
。感谢您的快速回复！我刚刚实现了解决方案，但是，应用程序的行为与以前相同。不幸的是，.isDetailLink（false）在watchOS中不可用。关于如何解决此问题或为什么我的应用程序会这样做，还有其他想法吗？@JPF哦，我明白了，我的错。你可以看到这个问题，我认为这也解释了如何在watchOS上工作。想法是一样的-你需要回到导航堆栈的根目录，以显示
AppMain
，而不是
>AppConfig
。