未触发根据modalView中的更改重新绘制ContentView

Question

自从swiftUI 2.0出现以来，我一直无法根据在另一个模式显示视图(设置视图(中所做的更改来更新视图。

我在主ContentView上显示一个字符串，该字符串从SettingsView上的分段选取器值派生其内容。问题是，在用户更改设置并放弃SettingsView后，ContentView中的字符串不会更新。正文未重新绘制。

我正在使用@ObservableObject和@StateObject，所以对它的每一次更改都应该触发重绘，但我无法使它工作。。。

我创建了一个符合ObservableObject协议的类：AppState我正在使用该类尝试传递数据，更重要的是，数据在视图之间更改，以便根据用户的设置重新绘制我的ContentView。为了实例化这个类，我在AppDelegate文件中注册了一个UserDefaults。

我还将Combine Framework导入到我的项目中，并在每个文件中添加了导入Combine行！

为了说明这个问题，我已经尽可能简化了我的代码，所以下面的内容可能看起来有点绕口，但它是从一个更复杂的应用程序中派生出来的，很抱歉。

这是我的ContentView代码：

import SwiftUI
import Combine

struct ContentView: View {

@StateObject var appState: AppState

@State var modalViewCaller = 0 // used to present correct modalView
@State var modalIsPresented = false // to present the modal views

var body: some View {

let stringArray = generateString() // func to generate string according to user's pref
let recapString = stringArray[0]

return ZStack {
NavigationView {
VStack {
// MARK: -  texts :
VStack {
Text(recapString)
.bold()
.multilineTextAlignment(/*@START_MENU_TOKEN@*/.center/*@END_MENU_TOKEN@*/)
} // end of VStack
.padding()
.overlay(RoundedRectangle(cornerRadius: 10)
.stroke(Color(UIColor.systemBlue), lineWidth: 4))
.padding()
} // END of VStack
.onAppear() {
self.modalViewCaller = 0
print("nn*********** Content View onAppear triggered ! ************n")
}
.navigationBarTitle("DataFun", displayMode: .inline)
.navigationBarItems(leading: (
Button(action: {
self.modalViewCaller = 1 // SettingsView
self.modalIsPresented = true
}
) {
Image(systemName: "gear")
.imageScale(.large)
}
))
} // END of NavigationView
.onAppear() {
self.appState.updateValues()
}
} // End of ZStack
.sheet(isPresented: $modalIsPresented) {
sheetContent(modalViewCaller: $modalViewCaller, appState: AppState())
}
.navigationViewStyle(StackNavigationViewStyle())
}

// MARK: - struct sheetContent() :

struct sheetContent: View {
@Binding var modalViewCaller: Int // Binding to the @State modalViewCaller variable from ContentView
@StateObject var appState: AppState

var body: some View {
if modalViewCaller == 1 { // The settings view is called
SettingsView(appState: AppState())
.navigationViewStyle(StackNavigationViewStyle())
.onDisappear { self.modalViewCaller = 0 }
} else if modalViewCaller == 2 { // the "other view" is called
OtherView()
.navigationViewStyle(StackNavigationViewStyle())
.onDisappear { self.modalViewCaller = 0 }
}
}
} // END of func sheetContent

// MARK: - generateString()
func generateString() -> [String] {

var recapString = "" // The recap string
var myArray = [""]

// We create the recap string :
if UserDefaults.standard.integer(forKey: "rules selection") == 0 { // ICAO
recapString = "User chose LEFT"
} else if UserDefaults.standard.integer(forKey: "rules selection") == 1 { // AF Rules
recapString = "User chose RIGHT"
}

myArray = [recapString]

return myArray
} // End of func generateString()
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView(appState: AppState())
}
}

这是我的AppState代码：

import Foundation
import SwiftUI
import Combine
class AppState: ObservableObject {
@Published var rulesSelection: Int = UserDefaults.standard.integer(forKey: "rules selection")

func updateValues() { // When the user changes a setting, the UserDefault is updated. Here, we align the AppState's value with what is now in the UserDefaults
self.rulesSelection = UserDefaults.standard.integer(forKey: "rules selection")
print("nappState value (ruleSelection) updated from Appstate class func "updateValues")
}
}

这是我的设置查看代码：

import SwiftUI
import Combine

struct SettingsView: View {

@Environment(.presentationMode) var presentationMode // in order to dismiss the Sheet
@StateObject var appState: AppState
@State private var rulesSelection = UserDefaults.standard.integer(forKey: "rules selection") // 0 is LEFT, 1 is RIGHT
var body: some View {
NavigationView {
VStack {
Spacer()
Text("Choose a setting below")
.padding()
Picker("", selection: $rulesSelection) {
Text("LEFT").tag(0)
Text("RIGHT").tag(1)
}
.pickerStyle(SegmentedPickerStyle())
.padding()
Spacer()
}
.navigationBarItems(
leading:
Button("Done") {
self.saveDefaults() // We set the UserDefaults
self.presentationMode.wrappedValue.dismiss() // This dismisses the view
//   self.modalViewCaller = 0
}
) // END of NavBarItems
} // END of NavigationBiew
} // END of body

func saveDefaults() {

UserDefaults.standard.set(rulesSelection, forKey: "rules selection")

self.appState.updateValues() // This is a func from the AppState class that will align the appState's value to the UserDefaults

}
}
struct SettingsView_Previews: PreviewProvider {
static var previews: some View {
SettingsView(appState: AppState())
}
}

如果有人有时间检查这个"工作项目"；live"：

https://github.com/Esowes/dataFun

谢谢你的指点。

谨致问候。

Answer 1

嗯。。。它是。。。简而言之，许多更改，所以这里是完整的ContentView.swift与修复。

注意：您只需要一个StateObject，并在其中设置一个实例，并且您需要在视图中发布可观察对象的属性，否则它不会刷新，并且在使用AppStorage等之前，UserDefaults中的更改不会刷新视图。

使用Xcode 12.1/iOS 14.1 进行验证

import SwiftUI
import Combine

struct ContentView: View {

@StateObject var appState: AppState

@State var modalViewCaller = 0 // used to present correct modalView
@State var modalIsPresented = false // to present the modal views

var body: some View {

return ZStack {
NavigationView {
VStack {
// MARK: -  texts :
VStack {
RecapStringView(appState: appState)
} // end of VStack
.padding()
.overlay(RoundedRectangle(cornerRadius: 10)
.stroke(Color(UIColor.systemBlue), lineWidth: 4))
.padding()
} // END of VStack
.onAppear() {
self.modalViewCaller = 0
print("nn*********** Content View onAppear triggered ! ************n")
}
.navigationBarTitle("DataFun", displayMode: .inline)
.navigationBarItems(leading: (
Button(action: {
self.modalViewCaller = 1 // SettingsView
self.modalIsPresented = true
}
) {
Image(systemName: "gear")
.imageScale(.large)
}
))
} // END of NavigationView
.onAppear() {
self.appState.updateValues()
}
} // End of ZStack
.sheet(isPresented: $modalIsPresented) {
sheetContent(modalViewCaller: $modalViewCaller, appState: appState)
}
.navigationViewStyle(StackNavigationViewStyle())
}

// MARK: - struct sheetContent() :

struct sheetContent: View {
@Binding var modalViewCaller: Int // Binding to the @State modalViewCaller variable from ContentView
@ObservedObject var appState: AppState

var body: some View {
if modalViewCaller == 1 { // The settings view is called
SettingsView(appState: appState)
.navigationViewStyle(StackNavigationViewStyle())
.onDisappear { self.modalViewCaller = 0 }
} else if modalViewCaller == 2 { // the "other view" is called
OtherView()
.navigationViewStyle(StackNavigationViewStyle())
.onDisappear { self.modalViewCaller = 0 }
}
}
} // END of func sheetContent
}
struct RecapStringView: View {
@ObservedObject var appState: AppState
var body: some View {
Text("User chose " + "(appState.rulesSelection == 0 ? "LEFT" : "RIGHT")")
.bold()
.multilineTextAlignment(.center)
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView(appState: AppState())
}
}