在SwiftUI中使用Toggle()按鈕時視圖消失

我在下面的代碼中有一個問題，每當我使用 Toggle()-Button 時，SettingsEx1View 都會消失，Exercise1View() 會出現。它們與 ObservableObject Profile() 相連。啟動應用程式時出現此錯誤，但似乎這是 Apple 必須修復的 SwiftUI 錯誤。奇怪的是，當我洗掉第 18 和 19 行時

    let osc = DynamicOscillator()
    let audioEngine = AudioEngine()

它作業得很好。有什么我忽略的或者你知道我能做些什么嗎？任何幫助表示贊賞，謝謝！

import SwiftUI
import AVFoundation
import AudioKit
import SoundpipeAudioKit
import Foundation

class Profile: ObservableObject {
    
    @Published var playSoundeffects = true
    @Published var waveformIndex = 0

}

struct Exercise1View: View {
    
    @EnvironmentObject var profile: Profile
        
    let osc = DynamicOscillator()
    let audioEngine = AudioEngine()
    
    var body: some View {
        NavigationLink(
            destination: SettingsEx1View())
        {
            Image(systemName: "gearshape.circle")
        }
            .navigationTitle("Exercise1")
    }
}

struct SettingsEx1View: View {
    
    @EnvironmentObject var profile: Profile
    let waveformOptions = ["sine", "triangle", "sawtooth", "square"]
    
    var body: some View {
            Form {
                Section(header: Text("General")) {
                    Toggle("play soundeffects", isOn: $profile.playSoundeffects)
                    Picker("waveform", selection: $profile.waveformIndex) {
                        ForEach(0 ..< waveformOptions.count) {
                            Text(self.waveformOptions[$0])
                        }
                    }
                }
            }
            .navigationTitle("Settings")
    }
}

struct HomeScreen: View {
    
    @EnvironmentObject var profile: Profile
    @AppStorage("playSoundeffects") var playSoundeffectsSave: Bool = true
    @AppStorage("waveform") var waveformIndexSave: Int = 0
    
    var body: some View {
        NavigationView{
                NavigationLink(destination: Exercise1View())
                {Text("Exercise1")}
        }
        .onAppear {
            profile.playSoundeffects = playSoundeffectsSave
            profile.waveformIndex = waveformIndexSave
        }
        .onChange(of: profile.playSoundeffects) { newValue in
            playSoundeffectsSave = profile.playSoundeffects
        }
        .onChange(of: profile.waveformIndex) { newValue in
            waveformIndexSave = profile.waveformIndex
        }
    }
}

struct ContentView: View {
    var body: some View {
        HomeScreen()
            .environmentObject(Profile())
    }
}

uj5u.com熱心網友回復：

HomeScreen.body取決于設定，因此Profile當后者更新時，它會被重繪 并作為NavigationView的一部分重新創建body，因此它的導航堆疊被破壞。

由于NavigationView不依賴于Profile自身，最簡單的解決方案是將其分離為獨立視圖，例如

struct HomeScreen: View {
    
    // ... other code
    
    var body: some View {
      MainView()
        .onAppear {
            profile.playSoundeffects = playSoundeffectsSave

    // ... other code
}

struct MainView: View {
  var body: some View {
        NavigationView{       // << here !!
                NavigationLink(destination: Exercise1View())
                {Text("Exercise1")}
        }
  }
}

有關更多資訊，另請參閱：https ://stackoverflow.com/a/72824345/12299030

標籤：IOS 迅速 迅捷

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