SwiftUI选项卡视图显示表

问题描述

我是SwiftUI的新手，我试图构建一个标签栏，其中包含一个标签，该标签将返回模式（工作表）但不返回视图。经过尝试，我发现有时它可以工作，但有时却不行。我想在用户取消模式后将上一个选项卡式项目作为所选选项卡。但是我找不到错误所在。有人向我解释我的代码有什么问题吗？

import SwiftUI
struct ContentView: View {
    @State var isPresenting = false
    @State private var selectedItem = 1
    @State private var oldSelectedItem = 1


    var body: some View {
        TabView(selection: $selectedItem){
            Text("1")
                .tabItem {
                        Image(systemName: "house")
                }.tag(1)
            .onAppear {
                self.oldSelectedItem = self.selectedItem
            }

            Text("")    // I want this to display the sheet.
                .tabItem { Image(systemName: "plus.circle") }
                .tag(2)
            .onAppear {
                self.isPresenting = true
                self.selectedItem = self.oldSelectedItem

            }

            Text("3")
                .tabItem {
                    Image(systemName: "calendar")
                }.tag(3)
            .onAppear {
                self.oldSelectedItem = self.selectedItem
            }
        }
        .sheet(isPresented: $isPresenting) {
            testSheet
        }
        .accentColor(Color.orange)

    
    }
    var testSheet : some View {
        vstack{
            Text("testing")
        }
    }
}

解决方法

我想你想要这个（经过Xcode 12 / iOS 14测试）

struct ContentView: View {
    @State var isPresenting = false
    @State private var selectedItem = 1
    @State private var oldSelectedItem = 1


    var body: some View {
        TabView(selection: $selectedItem){
            Text("1")
                .tabItem {
                        Image(systemName: "house")
                }.tag(1)

            Text("")    // I want this to display the sheet.
                .tabItem { Image(systemName: "plus.circle") }
                .tag(2)

            Text("3")
                .tabItem {
                    Image(systemName: "calendar")
                }.tag(3)
        }
     //   .onReceive(Just(selectedItem))  // SwiftUI 1.0 - import Combine for this
        .onChange(of: selectedItem) {    // SwiftUI 2.0 track changes
                if 2 == selectedItem {
                self.isPresenting = true
                } else {
                    self.oldSelectedItem = $0
                }
            }
        .sheet(isPresented: $isPresenting,onDismiss: {
                self.selectedItem = self.oldSelectedItem
            }) {
            testSheet
        }
        .accentColor(Color.orange)


    }
    var testSheet : some View {
        VStack{
            Text("testing")
        }
    }
}