如何在 SwiftUI 中一个接一个地显示多个警报对话框？

Question

以下代码显示了一个“删除文件”按钮。当用户按下它时，会出现一个确认警报对话框。当用户在第一个对话框上按“删除”时，我想显示第二个警报对话框，确认文件已被删除。但是，它从未出现，即使调试代码确认第二个“return Alert...”语句实际上正在按预期执行。有没有办法让第二个警报也出现？

import SwiftUI

enum alertShownType {
    case alertNone, alertDeleteFile,alertFileDeleted
}

struct ContentView: View {

    @State var showingAlert = false
    @State var alertShown: alertShownType = alertShownType.alertNone

    var body: some View {
        Button(action: {
            self.alertShown = alertShownType.alertDeleteFile
            self.showingAlert = true
        })
        {
            Text("Delete file")
        }.padding(EdgeInsets(top: 0, leading: 0, bottom: 10, trailing:0))
        .alert(isPresented: $showingAlert, content: {
            if (alertShown == alertShownType.alertDeleteFile)
            {
                return Alert(title: Text("Delete file"),
                      message: Text("Are you sure?"),
                      primaryButton: .destructive(Text("Delete")) {

                        // Delete the file

                        ....

                        // Show the next alert
                        alertShown = alertShownType.alertFileDeleted
                        showingAlert = true
                      },
                      secondaryButton: .cancel())
            }
            else // alertFileDeleted
            {
                return Alert(title: Text("File deleted"), message:
                            Text("Done!"),
                      dismissButton: .default(Text("OK")))
            }
        })
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

Answer 1

你只需要

public func alert<Item>(item: Binding<Item?>, content: (Item) -> Alert)

不需要@State var showingAlert = false 标志。

像这样设置你的代码

enum alertShownType : Identifiable {
    case alertNone,
    alertDeleteFile,
    alertFileDeleted

    var id : Int { get {
        hashValue
    }}
}

struct ContentViewAlerts: View {

    @State var alertShown: alertShownType?
    
    var body: some View {
        Button(action: {
            self.alertShown = alertShownType.alertDeleteFile
        })
        {
            Text("Delete file")
        }.padding(EdgeInsets(top: 0, leading: 0, bottom: 10, trailing:0))
        .alert(item: $alertShown, content: { alertType in
            if (alertShown == alertShownType.alertDeleteFile)
            {
                return Alert(title: Text("Delete file"),
                             message: Text("Are you sure?"),
                             primaryButton: .destructive(Text("Delete")) {
                                
                                // Delete the file
                                
                                //                                ....
                                
                                // Show the next alert
                                alertShown = alertShownType.alertFileDeleted
                             },
                             secondaryButton: .cancel())
            }
            else // alertFileDeleted
            {
                return Alert(title: Text("File deleted"), message:
                                Text("Done!"),
                             dismissButton: .default(Text("OK")))
            }
        })
    }
}