如何使用 SwiftUI 连续呈现两个警报视图 [英] How to consecutively present two alert views using SwiftUI

问题描述

我想在点击第一个警报视图的关闭按钮后立即显示第二个警报视图.

I want to immediately present the second alert view after click the dismiss button of the first alert view.

Button(action: {
     self.alertIsVisible = true
}) {
     Text("Hit Me!")
}
.alert(isPresented: $alertIsVisible) { () -> Alert in
    return Alert(title: Text("\(title)"), message: Text("\n"), dismissButton:.default(Text("Next Round"), action: {
        if self.score == 100 {
            self.bonusAlertIsVisible = true
    }
    .alert(isPresented: $bonusAlertIsVisible) {
        Alert(title: Text("Bonus"), message: Text("You've earned 100 points bonus!!"), dismissButton: .default(Text("Close")))}
})
)

但是，它给了我一个错误:Alert.Button"不能转换为Alert.Button?"如果我将此段置于dismissButton 的范围之外，它将覆盖之前的.alert.那么我该怎么做，我只想在单击第一个警报的关闭按钮后弹出第二个警报.谢谢.

However, it gives me an error of 'Alert.Button' is not convertible to 'Alert.Button?' If I put this segment out of the scope of dismissButton, it will override the previous .alert. So how can i do it, I just want to pop up the second alert after clicking the dismiss button of the first alert. Thanks.

推荐答案

出现(使用 Xcode 11.2 测试):

It appears (tested with Xcode 11.2):

1. 虽然没有记录，但不允许添加多个.alert 修饰符在一个视图构建器序列中 - 仅适用于最新
2. 不允许向EmptyView添加.alert修饰符，它不起作用完全

我找到了@Rohit 提出的替代解决方案.在某些情况下，有很多警报，这可能会导致代码更简单.

I've found alternate solution to proposed by @Rohit. In some situations, many alerts, this might result in simpler code.

struct TestTwoAlerts: View {
    @State var alertIsVisible = false
    @State var bonusAlertIsVisible = false

    var score = 100
    var title = "First alert"

    var body: some View {
        VStack {
            Button(action: {
                 self.alertIsVisible = true
            }) {
                 Text("Hit Me!")
            }
            .alert(isPresented: $alertIsVisible) {
                Alert(title: Text("\(title)"), message: Text("\n"), dismissButton:.default(Text("Next Round"), action: {
                    if self.score == 100 {
                        DispatchQueue.main.async { // !! This part important !!
                            self.bonusAlertIsVisible = true
                        }
                    }
                }))
            }
            Text("")
            .alert(isPresented: $bonusAlertIsVisible) {
                    Alert(title: Text("Bonus"), message: Text("You've earned 100 points bonus!!"), dismissButton: .default(Text("Close")))
            }
        }
    }
}

struct TestTwoAlerts_Previews: PreviewProvider {
    static var previews: some View {
        TestTwoAlerts()
    }
}

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