使用SwiftUI'；s页面选项卡视图样式选项卡视图

使用Swift5.3.2、iOS14.4.2、XCode12.4、

我试图在SwiftUI中创建一个页面视图，使用iOS14新的

PageTabViewStyle

作为选项卡视图

页面应能在页面之间顺利交换

只要我没有以任何方式对

selectedIndex

执行任何类型的

onChange

-操作，这一切都可以正常工作

一旦我做了

.onChange（of:selectedIndex）{newidx in…}

，那么刷卡就很慢，不再适用于可用性

但我的应用程序需要跟踪页面索引，并且需要在任何索引更改时执行代码

如何在SwiftUI的页面视图中检测到刷卡操作？？

我意识到，只要我使用任何类型的

.onReceive（）

或

.onChange（of:）

和

selectedIndex

或其任何发布者，我总是会以不再平滑的滑动手势结束

如何克服此问题并获得平滑的滑动和索引信息

这是我的密码：

struct CustomPageView: View {
    
    @ObservedObject var myPageSelectionService = PageSelectionService()
    @State private var contents = ["a","b","c"]
    @State private var selectedIndex: Int = 0
            
    var body: some View {
            
        TabView(selection: $selectedIndex) {
            ForEach(0..<contents.count, id:\.self) { i in
                Text(contents[i]).tag(i)
            }
        }
        .tabViewStyle(PageTabViewStyle(indexDisplayMode: .automatic))
        .onChange(of: selectedIndex) { newIndex in
            print(newIndex)
        }
    }
}

怎么办

以下是整个应用程序（如果好奇）：

import SwiftUI

enum MyState {
    case waiting
    case running
}

class AppState: ObservableObject {
    
    @Published var myState: MyState = .running
}

class MyService: ObservableObject {
    
    @Published var someServiceValue = 0
}

struct MainView: View {
    
    @StateObject var appState = AppState()
    @StateObject var myService = MyService()
    
    var body: some View {
        ParentView()
            .environmentObject(appState)
            .environmentObject(myService)
    }
}

struct ParentView: View {
    
    @EnvironmentObject var appState: AppState
    @EnvironmentObject var myService: MyService
        
    var body: some View {
        
        NavigationView {
            
            ZStack {
        
                switch appState.myState {
                case .waiting:
                    Text("Waiting")
                case .running:
                    ChildView()
                }
            }
        }
        .navigationViewStyle(StackNavigationViewStyle())
        .onChange(of: myService.someServiceValue) { newValue in
            if newValue == 4 {
                appState.myState = .waiting
            }
        }
    }
}

struct ChildView: View {
    
    @EnvironmentObject var myService: MyService
    
    @State private var contents = ["img_team_ivo","img_team_beat","img_team_benny","img_team_irfan","img_team_jenny","img_team_lukas","img_team_sabrina","img_team_nici","img_team_pascal","img_team_patrick","img_team_silvan","img_team_stephan","img_team_christoph"]
    @State private var selectedIndex: Int = 0
    
    var body: some View {
        
        ZStack {
            ScrollView {
                ZStack {
                    TabView(selection: $selectedIndex) {
                        ForEach(0..<contents.count, id:\.self) { index in
                            ZStack {
                                Image(contents[index])
                                    .resizable()
                                    .scaledToFit()
                            }
                        }
                    }
                    .tabViewStyle(PageTabViewStyle(indexDisplayMode: .automatic))
                }
            }
        }
        
        .onChange(of: selectedIndex) { newIdx in
            // !!!!!!!!!! app stalls - no more smooth swiping of Pages :(
            myService.someServiceValue = newIdx
        }
    }
}

导入快捷界面
我的国家{
案件等待
案件审理
}
类AppState:ObservableObject{
@已发布的变量myState:myState=.running
}
类MyService:observeObject{
@已发布的变量someServiceValue=0
}
结构主视图：视图{
@StateObject变量appState=appState（）
@StateObject变量myService=myService（）
var body：一些观点{
父视图（）
.environmentObject（appState）
.environmentObject（myService）
}
}
结构父视图：视图{
@EnvironmentObject变量appState:appState
@环境对象变量myService:myService
var body：一些观点{
导航视图{
ZStack{
开关appState.myState{
案件.等候：
文本（“等待”）
案例.运行：
ChildView（）
}
}
}
.navigationViewStyle（StackNavigationViewStyle（））
.onChange（of:myService.someServiceValue）{newValue in
如果newValue==4{
appState.myState=.waiting
}
}
}
}
结构子视图：视图{
@环境对象变量myService:myService
@国家私人var内容=[“img_团队ivo”、“img_团队beat”、“img_团队benny”、“img_团队irfan”、“img_团队jenny”、“img_团队lukas”、“img_团队sabrina”、“img_团队nici”、“img_团队pascal”、“img_团队patrick”、“img_团队silvan”、“img_团队stephan”、“img_团队christoph”]
@状态私有变量selectedIndex:Int=0
var body：一些观点{
ZStack{
滚动视图{
ZStack{
选项卡视图（选择：$selectedIndex）{
ForEach（0。。
import SwiftUI

enum MyState {
    case waiting
    case running
}

class AppState: ObservableObject {
    
    @Published var myState: MyState = .running
}

class MyService: ObservableObject {
    
    @Published var someServiceValue = 0
}

struct MainView: View {
    
    @StateObject var appState = AppState()
    @StateObject var myService = MyService()
    
    var body: some View {
        ParentView()
            .environmentObject(appState)
            .environmentObject(myService)
    }
}

struct ParentView: View {
    
    @EnvironmentObject var appState: AppState
    @EnvironmentObject var myService: MyService
        
    var body: some View {
        
        NavigationView {
            
            ZStack {
        
                switch appState.myState {
                case .waiting:
                    Text("Waiting")
                case .running:
                    ChildView()
                }
            }
        }
        .navigationViewStyle(StackNavigationViewStyle())
        .onChange(of: myService.someServiceValue) { newValue in
            if newValue == 4 {
                appState.myState = .waiting
            }
        }
    }
}

struct ChildView: View {
    
    @EnvironmentObject var myService: MyService
    
    @State private var contents = ["img_team_ivo","img_team_beat","img_team_benny","img_team_irfan","img_team_jenny","img_team_lukas","img_team_sabrina","img_team_nici","img_team_pascal","img_team_patrick","img_team_silvan","img_team_stephan","img_team_christoph"]
    @State private var selectedIndex: Int = 0
    
    var body: some View {
        
        ZStack {
            ScrollView {
                ZStack {
                    TabView(selection: $selectedIndex) {
                        ForEach(0..<contents.count, id:\.self) { index in
                            ZStack {
                                Image(contents[index])
                                    .resizable()
                                    .scaledToFit()
                            }
                        }
                    }
                    .tabViewStyle(PageTabViewStyle(indexDisplayMode: .automatic))
                }
            }
        }
        
        .onChange(of: selectedIndex) { newIdx in
            // !!!!!!!!!! app stalls - no more smooth swiping of Pages :(
            myService.someServiceValue = newIdx
        }
    }
}