SwiftUI：使用“if else”更改视图

Posted 2023-02-24

【中文标题】SwiftUI：使用“if else”更改视图

【英文标题】：SwiftUI: changing view using "if else"

【发布时间】：2020-05-30 01:47:19

【问题描述】：

我正在尝试根据使用按钮进行的​​选择来更改视图。我正在使用 Combine 和 SwiftUI。

我创建了一个带有@Published var: 的视图路由器类：

import Foundation
import SwiftUI
import Combine

class ViewRouter: ObservableObject 

    @Published var currentView = "folder"

我有我的按钮结构：

import SwiftUI
import Combine

struct MultiButton: View 
    @ObservedObject var viewRouter = ViewRouter()
    @State var showButton = false

    var body: some View 
        GeometryReader  geometry in
            ZStack

                // open multi button
                Button(action: 

                    withAnimation 
                        self.showButton.toggle()
                    
                ) 
                    Image(systemName: "gear")
                        .resizable()
                        .frame(width: 40, height: 40, alignment: .center)
                
                if self.showButton 

                    Multi()
                    .offset(CGSize(width: -30, height: -100))
                
            


        
    


struct MultiButton_Previews: PreviewProvider 
    static var previews: some View 
        MultiButton()
    


struct Multi: View 

 @ObservedObject var viewRouter = ViewRouter()

    var body: some View 
        HStack(spacing: 10) 
            ZStack 

                Button(action: 
                    self.viewRouter.currentView = "folder"
                     debugPrint("\(self.viewRouter.currentView)")
                ) 
                    ZStack

                    Circle()
                        .foregroundColor(Color.blue)
                        .frame(width: 70, height: 70)
                    Image(systemName: "folder")
                        .resizable()
                        .aspectRatio(contentMode: .fit)
                        .padding(20)
                        .frame(width: 70, height: 70)
                        .foregroundColor(.white)
                    .shadow(radius: 10)
                
            

            Button(action: 
                self.viewRouter.currentView = "setting"
                debugPrint("\(self.viewRouter.currentView)")
            , label: 
                ZStack 
                    Circle()
                        .foregroundColor(Color.blue)
                        .frame(width: 70, height: 70)
                    Image(systemName: "gear")
                        .resizable()
                        .aspectRatio(contentMode: .fit)
                        .padding(20)
                        .frame(width: 70, height: 70)
                        .foregroundColor(.white)
                .shadow(radius: 10)
            )
        
            .transition(.scale)
    

还有contentView：

import SwiftUI
import Combine

struct ContentView: View 
    @ObservedObject var viewRouter = ViewRouter()
    var body: some View 
        VStack

            MultiButton()

            if viewRouter.currentView == "folder" 
                Text("folder")
             else if viewRouter.currentView == "setting"
                Text("setting")
            
        
    

为什么按下按钮时我的文本没有从文件夹更改为设置基础？

变量是@Published；它应该发布更改并更新主视图。

我错过了什么吗？

【参考方案1】：

您有多个 ViewRouter 实例，每个视图都有自己的实例。如果您更改该实例，则其他实例不会更改。

要解决这个问题，您要么必须手动传递一个实例：

struct MultiButton 
    @ObservedObject var viewRouter: ViewRouter
    ...


struct ContentView 
    @ObservedObject var viewRouter = ViewRouter()
    var body: some View 
        VStack 
            MultiButton(viewRouter: self.viewRouter)
            ...
        
    

或者您可以将其声明为环境对象：

struct MultiButton 
    @EnvironmentObject var viewRouter: ViewRouter
    ...

然后注入它，例如当您在场景委托中创建视图层次结构时：

let contentView = ContentView()
    .environmentObject(ViewRouter())

请注意，在场景委托中注入环境对象时，它不会在使用 ViewRouter 的视图的每个预览中都可用，除非您也手动将其注入那里：

static var previews: some View 
    ContentView()
    .environmentObject(ViewRouter())