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在使用 开发iOS应用程序SwiftUI时，我面临以下情况。我已经设置了一个自定义环境键。这是SceneDelegate.swift文件中的相关代码。

private struct RowColorMaster: EnvironmentKey {
    static var defaultValue: Binding<[[String:Color]]> = .constant([[:]])
}

extension EnvironmentValues {
    var rowColorMasterDico: Binding<[[String:Color]]> {
        get {self[RowColorMaster.self]}
        set {self[RowColorMaster.self] = newValue}
    }
}


class SceneDelegate: UIResponder, UIWindowSceneDelegate {
    var window: UIWindow?
    var rowColorMasterDico:[[String:Color]] = []

    func scene(_ scene: UIScene, 
               willConnectTo session: UISceneSession, 
               options connectionOptions: UIScene.ConnectionOptions) {
        .....
        let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
        .....
        rowColorMasterDico = .....

        print("rowColorMasterDico -> \(rowColorMasterDico.count)")

        let contentView = ContentView(sectionsList: sectionsList,
                                      itemMasterList: sentceMasterArray)
                                .environment(\.managedObjectContext, context)
                                .environment(\.rowColorMasterDico,
                                             Binding(get: {self.rowColorMasterDico},
                                                     set: {
                                                        newValue in
                                                        self.rowColorMasterDico = newValue
                                                     }))
        .....
    }
    .....
}

然后再往下，在视图层次结构中，在一些视图文件中：

struct SectionView: View {
    var moc:NSManagedObjectContext
    .....
    @Environment(\.rowColorMasterDico) var rowColorMasterDico
    .....

    func handleEvent(_ file: String, flag: Bool) {
        // This function is called when an audio file
        // starts or ends playing.
        if rowColorMasterDico.wrappedValue.count != 10 {
            // This should not happen! But for some reason it sometimes does.
            print("rowColorMasterDico is messed up !")
            return
        }

        // Check that rowColorMasterDico.wrappedValue[page.index][file] changes value.
        print("CLR(Before)=\(rowColorMasterDico.wrappedValue[page.index][file]!)")
        rowColorMasterDico.wrappedValue[page.index][file] = flag ? Color.red : Color.white
        print("CLR(After)=\(rowColorMasterDico.wrappedValue[page.index][file]!)")
    }
    .....


    var body: some View {
        VStack {
            ListItemView(itemList: itmMstrList[page.index], moc: moc,
                         rowColorDico: rowColorMasterDico.wrappedValue[page.index])
            Button(action: {
                if !soundManager.isPlaying {self.playAllAudio(itmMstrList[page.index])}
                else {soundManager.stopAudio()}
            })
            {
                Image(uiImage: UIImage(named: "speaker.png")!)
                    .padding(.bottom, 17)
            }
        }
    }
    .....


struct ListItemView: View {
    let crnrRad:CGFloat = 13.0, bgGreyLvl = 0.37, fgGreyLvl = 0.93
    var itemList:[ItemList], moc:NSManagedObjectContext
    @State var rowColorDico:[String:Color]

    .....
    
    func didDismiss() {
        // Handle the dismissing action.
        print(#function)
    }
    
    var body: some View {
        List {
            ForEach(self.itemList) {
                item in
                HStack {
                    Spacer()
                    Button(action: {
                        self.handleRowItem(item)
                    })
                    {
                        RowItemView(expression: item.expression!,
                                    fgTxtColor: rowColorDico[item.soundFile!] ?? Color.orange)
                    }
                    Spacer()
                }
            }
        }.sheet(item: $itemPage, onDismiss: didDismiss) {
            sntnc in
            .....
        }
        
    }
}


struct RowItemView: View {
    var expression:String
    @State var fgTxtColor:Color
    let crnrRad:CGFloat = 13.0, bgGreyLvl = 0.37
    
    var body: some View {
        Text(expression)
            .foregroundColor(fgTxtColor)
            .font(.headline)
            .padding(.horizontal, 11).padding(.vertical, 15)
            .background(Color(.sRGB, red: bgGreyLvl, green: bgGreyLvl,
                              blue:bgGreyLvl, opacity: 1.0))
            .cornerRadius(crnrRad)
            .overlay(RoundedRectangle(cornerRadius: crnrRad)
                    .stroke(Color.yellow, lineWidth: 3))
    }
}

这是问题所在。当我在 ListItemView 中播放音频文件列表时，匹配的行项目应该改变播放文件的颜色。为此的工作是在 handleEvent 函数中完成的，我可以检查这是否按预期发生。但是列表中显示的颜色并没有改变。这是为什么？

我设置环境变量rowColorMasterDico的方式有误吗？还是我错过了其他东西？我已经尝试了上面代码的许多不同变体，但我无法使其工作。我希望有人会在某个地方看到并指出错误。

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1 回答 1

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以防万一这对其他人有用，我想报告我通过参考这个解决了我的问题，同时再看一下我自己的代码。

于 2021-05-03T09:25:10.540 回答