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swift - 发生状态更改时 UISegmentedControl 不更改

问题描述

下面我有我的选择器的代码：

struct pickerSwitch: View {
  @ObservedObject var appState: AppState
  @State var selection: String = "Red"
  var colors = ["Red", "Blue"]

  init(appState: AppState) {
        print("Init ran again")
        self.appState = appState
        if appState.showBlueControl {
            UISegmentedControl.appearance().setTitleTextAttributes([.font : UIFont.preferredFont(forTextStyle: .headline)], for: .normal)
            UISegmentedControl.appearance().backgroundColor = .blue
        } else {
            UISegmentedControl.appearance().setTitleTextAttributes([.font : UIFont.preferredFont(forTextStyle: .headline)], for: .normal)
            UISegmentedControl.appearance().backgroundColor = .red
        }
    }

  var body: some View {
        Picker(selection: $selection, label: Text("")) {
            ForEach(colors, id: \.self) {
                Text($0)
            }
        }.pickerStyle(SegmentedPickerStyle())
  }
}

在我的代码的其他地方，我有一个按钮可以更改“AppState”特定实例的“showBlueControl”值。在我的 Xcode 日志中，我看到很多“再次运行初始化”日志，所以我认为分段控件应该发生变化，但由于某种原因，只有在我完全关闭视图并重新打开它时才会发生变化。当 SwiftUI 状态发生变化（不关闭/重新打开视图）时，如何动态更改 SegmentedControl？

标签： swiftxcodeswiftuisegmentedcontrol

解决方案

您只需要@State跟踪背景颜色。然后你.background()在选择器上设置。要更改您的状态变量，只需使用.onChange.

struct PickerSwitch: View {
    @State var selection: String = "Red"
    var colors = ["Red", "Blue"]
    @State var backgroundColor = Color.red // This tracks your background color
    
    var body: some View {
        Picker(selection: $selection, label: Text("")) {
            ForEach(colors, id: \.self) {
                Text($0)
            }
        }
// .onChange reacts to the change of selection
        .onChange(of: selection, perform: { value in 
            if value == "Red" {
                backgroundColor = .red
            } else {
                backgroundColor = .blue
            }
        })
        .pickerStyle(SegmentedPickerStyle())
        .background(backgroundColor) // Set your background color here
    }
}

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