SwiftUI View 保持暗黑模式中的一种不变

需求： 不需要暗黑模式但是不想在info.plist里面全局关闭暗黑模式

• 苹果源码 .preferredColorScheme(.dark)

代码

@available(iOS 13.0, macOS 11.0, tvOS 13.0, watchOS 6.0, *)
extension View {

    /// Sets the preferred color scheme for this presentation.
    ///
    /// Use one of the values in ``ColorScheme`` with this modifier to set a
    /// preferred color scheme for the nearest enclosing presentation, like a
    /// popover, a sheet, or a window. The value that you set overrides the
    /// user's Dark Mode selection for that presentation. In the example below,
    /// the ``Toggle`` controls an `isDarkMode` state variable, which in turn
    /// controls the color scheme of the sheet that contains the toggle:
    ///
    ///     @State private var isPresented = false
    ///     @State private var isDarkMode = true
    ///
    ///     var body: some View {
    ///         Button("Show Sheet") {
    ///             isPresented = true
    ///         }
    ///         .sheet(isPresented: $isPresented) {
    ///             List {
    ///                 Toggle("Dark Mode", isOn: $isDarkMode)
    ///             }
    ///             .preferredColorScheme(isDarkMode ? .dark : .light)
    ///         }
    ///     }
    ///
    /// If you apply the modifier to any of the views in the sheet --- which in
    /// this case are a ``List`` and a ``Toggle`` --- the value that you set
    /// propagates up through the view hierarchy to the enclosing
    /// presentation, or until another color scheme modifier higher in the
    /// hierarchy overrides it. The value you set also flows down to all child
    /// views of the enclosing presentation.
    ///
    /// A common use for this modifier is to create side-by-side previews of the
    /// same view with light and dark appearances:
    ///
    ///     struct MyView_Previews: PreviewProvider {
    ///         static var previews: some View {
    ///             MyView().preferredColorScheme(.light)
    ///             MyView().preferredColorScheme(.dark)
    ///         }
    ///     }
    ///
    /// If you need to detect the color scheme that currently applies to a view,
    /// read the ``EnvironmentValues/colorScheme`` environment value:
    ///
    ///     @Environment(\.colorScheme) private var colorScheme
    ///
    ///     var body: some View {
    ///         Text(colorScheme == .dark ? "Dark" : "Light")
    ///     }
    ///
    /// - Parameter colorScheme: The preferred color scheme for this view.
    ///
    /// - Returns: A view that sets the color scheme.
    @inlinable public func preferredColorScheme(_ colorScheme: ColorScheme?) -> some View

}