Question

我在关闭工作表后试图显示警报。但是，当我更新工作表中的@Binding时，主页中的警报没有出现。我不知道现在是什么问题。有人可以向我解释吗？这是使用@Binding的问题吗？如果执行此操作的方法/逻辑错误，应该使用哪种方法？

struct ContentView: View {
    @State private var showSheet = false
    @State var showAlert = false

    var body: some View {
        VStack {
            Text("sheet")
                .onTapGesture(perform: {
                    self.showSheet.toggle()
                })
        }
        .sheet(isPresented: $showSheet) {
            AddView(showAlert: self.$showAlert, showSheet: self.$showSheet)
        }
        .alert(isPresented: $showAlert){
            Alert(title: Text("Important message"), message: Text("Wear sunscreen"), dismissButton: .default(Text("Got it!")))
        }
    }

}
struct AddView: View {
    @Binding var showAlert: Bool
    @Binding var showSheet: Bool

    var body: some View {
        Button("Dismiss") {
            self.showSheet = false
            self.showAlert = true
        }
    }
}

Answer 1

Sheet具有不同的上下文，因此像在原始代码中那样设置的警报在此处不可见。

这里是修改后的代码，可以正常工作。经过Xcode 12.1 / iOS 14.1的测试

struct ContentView: View {
    @State private var showSheet = false
    @State var showAlert = false

    var body: some View {
        VStack {
            Text("sheet")
                .onTapGesture(perform: {
                    self.showSheet.toggle()
                })
        }
        .sheet(isPresented: $showSheet, onDismiss: { self.showAlert = true }) {
            AddView(showSheet: self.$showSheet)
        }
        .alert(isPresented: $showAlert){
            Alert(title: Text("Important message"), message: Text("Wear sunscreen"), dismissButton: .default(Text("Got it!")))
        }
    }

}
struct AddView: View {
    @Binding var showSheet: Bool

    var body: some View {
        Button("Dismiss") {
            self.showSheet = false
        }
    }
}

Answer 2

真正的问题是您试图解散工作表并同时显示警报。在您的代码中，如果您向警报添加0.5秒的延迟，它将起作用：

struct AddView: View {
        @Binding var showAlert: Bool
        @Binding var showSheet: Bool

        var body: some View {
            Button("Dismiss") {
                self.showSheet = false
                DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) {
                    self.showAlert = true
                }
            }
        }
    }

但是，这样写起来要干净得多：

struct ContentView: View {

    @State private var showSheet = false
    @State var showAlert = false

    var body: some View {
        VStack {
            Button(action: {
                self.showSheet.toggle()
            }, label: {
                Text("sheet")
            })
            .accentColor(.primary)
        }
        .sheet(isPresented: $showSheet, onDismiss: showAlertFunction, content: {
            AddView()
        })
        .alert(isPresented: $showAlert){
            Alert(title: Text("Important message"), message: Text("Wear sunscreen"), dismissButton: .default(Text("Got it!")))
        }
    }
    
    func showAlertFunction() {
        showAlert.toggle()
    }

}

struct AddView: View {

    @Environment(\.presentationMode) var presentationMode
    
    var body: some View {
        Button("Dismiss") {
            self.presentationMode.wrappedValue.dismiss()
        }
    }
}

SwiftUI @Binding没有更新显示警报

2 个答案: