SwiftUI 显示警报的问题 – 不会显示警报框

Question

我有以下代码：

@State private var signoutAlert = false

var body: some View {

    Button(action: {
      
        self.signoutAlert = true
        
        print("signout button clicked")
        
    }) {
        
        Text("Sign Out")
    
    }
    .alert(isPresented: $signoutAlert) {
        
        print(".alert will display")
        //
        return Alert(title: Text("Sign Out"), message: Text("Are you sure you want to Sign Out?"), primaryButton: .destructive(Text("Sign Out")) {
            
            print("Signing out....")
          
            self.session.signOut()

            self.presentationMode.wrappedValue.dismiss()
            
        }, secondaryButton: .cancel())
    
    }

}

打印出以下输出：

1. 退出按钮被点击
2. .alert 将显示

我希望通过单击两个按钮之一来显示警报框并提示用户“取消”或“退出”；但它从不显示或提示用户，这是没有意义的！？

有没有人看到我的代码有什么问题！？这非常令人沮丧，因为它应该非常简单！？

Answer 1

I had the same problem but realized this is now a deprecated .alert modifier. When I moved to using the newer modifier, it worked fine. Example from Apple's documentation:

        .alert(title, isPresented: $didFail) {
            Button("OK") {
                // Handle acknowledgement.
            }
        } message: {
            Text("Please ensure your credentials are correct.")
        }

Answer 2

感谢@ken-chin-purcell，他的回答帮助我找到了更方便的解决方法。

只需将警报放在 EmptyView 下即可：

    .overlay(
        EmptyView()
            .alert(isPresented: $showAlert1) {
                Alert(
                    title: ...,
                    message: ...,
                    ...
                )
            },
        alignment: .bottomTrailing
    )
    .overlay(
        EmptyView()
            .alert(isPresented: $showAlert2) {
                Alert(
                    title: ...,
                    message: ...,
                    ...
                )
            },
        alignment: .bottomTrailing
    )

或者使用扩展：

extension View {
    public func alertPatched(isPresented: Binding<Bool>, content: () -> Alert) -> some View {
        self.overlay(
            EmptyView().alert(isPresented: isPresented, content: content),
            alignment: .bottomTrailing
        )
    }
}

Answer 3

当视图层次结构中的视图上有一个 .alert(...) 视图修饰符时，我遇到了这个问题。如果父视图定义了 .alert() ，那么子视图的 .alert() 修饰符将不会显示它的警报。

就我而言，我将高级视图上的 .alert() 向下移动为触发它的按钮上的修饰符，现在两个警报都正确显示。例如：

struct HiddenWalrusView: View {
    @State private var showAlert1 = false
    @State private var showAlert2 = false
    
    var body: some View {
        VStack {
            Button("Show Alert One") { showAlert1 = true }
                .padding(20)
            Button("Show Alert Two") { showAlert2 = true }
                .padding(20)
                .alert(isPresented: $showAlert2) {
                    // This alert never displays
                    Alert(title: Text("I am the Walrus"))
                }
        }
        .alert(isPresented: $showAlert1) {
            Alert(title: Text("I am the Egg Man"))
        }
    }
}

struct EggmanAndWalrusView: View {
    @State private var showAlert1 = false
    @State private var showAlert2 = false
    
    var body: some View {
        VStack {
            Button("Show Alert One") { showAlert1 = true }
                .padding(20)
                .alert(isPresented: $showAlert1) {
                    Alert(title: Text("I am the Egg Man"))
                }
            Button("Show Alert Two") { showAlert2 = true }
                .padding(20)
                .alert(isPresented: $showAlert2) {
                    Alert(title: Text("I am the Walrus"))
                }
        }
    }
}