聆听环境变化 [英] Listen for Environment Changes

问题描述

如何检测 SwiftUI 中的环境变化?例如，我将当前的配色方案存储为

How do I detect environment changes in SwiftUI? For example, I store the current colour scheme as

@Environment(\.colorScheme) var colorScheme: ColorScheme

我根据环境值显示一个ASAuthorizationAppleIDButton:

And I display an ASAuthorizationAppleIDButton based on the environment value:

fileprivate struct AppleSignInView : UIViewRepresentable {

    var colorScheme: ColorScheme

    func makeUIView(context: Context) -> ASAuthorizationAppleIDButton {
        switch colorScheme {
        case .light:
            return ASAuthorizationAppleIDButton(type: .continue, style: .black)

        case .dark:
            return ASAuthorizationAppleIDButton(type: .continue, style: .white)

        @unknown default:
            return ASAuthorizationAppleIDButton(type: .continue, style: .black)
        }
    }

    func updateUIView(_ uiView: ASAuthorizationAppleIDButton, context: Context) { }
}

并且在我的 body 属性中，我实例化了结构:

And In my body property I instantiate the struct:

var body: some View {
    AppleSignInView(colorScheme: colorScheme)
}

这很好用，但是当我从 Xcode 更改配色方案时，新配色方案不会传播.

This works fine, but the new colour scheme isn't propagated when I change the colour scheme from the Xcode.

如何监听这个环境变量的变化?

How do I listen to this environment variable change?

推荐答案

我是这样做的:诀窍是添加 .id(self.colorScheme) 行.这会强制 SwiftUI 在每次 colorScheme 更改时重绘此按钮.

Here is how I do it: the trick is to add the .id(self.colorScheme) line. This forces SwiftUI to redraw this button every time the colorScheme changes.

SignInWithAppleButton(style: self.colorScheme == .light ? .black : .white)
  .frame(width: 280, height: 60)
  .onTapGesture(perform: self.showAppleLogin)
  .id(self.colorScheme)

这样可以避免在 if/else 语句中返回两个版本的按钮，就像在 kontiki 的回答中一样.

This saves you from returning 2 versions of the button in an if/else statement, like in kontiki's answer.

还有我的按钮，很好:

struct SignInWithAppleButton: UIViewRepresentable {
  var style: ASAuthorizationAppleIDButton.Style

  func makeUIView(context: Context) -> ASAuthorizationAppleIDButton {
    return ASAuthorizationAppleIDButton(type: .default, style: style)
  }

  func updateUIView(_ uiView: ASAuthorizationAppleIDButton, context: Context) {}
}

这篇关于聆听环境变化的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！