SwiftUI：为特定视图设置状态栏颜色

Question

i have been trying to set the status bar colour of my application for just a single view.

i have tried the solution listed here..' How to change Status Bar text color in iOS ' but that sets it for the whole application.

What i want is the status bar colour to have white text for the rootViewController set in SceneDelegate.swift and then be defaulted (change from white to black depending on dark mode) for all other views.

any ideas?

Answer 1

Status bar content color can be modified per view controller based, but SwiftUI uses, most usually, only one view controller, root hosting view controller. So it needs to push that root controller to change preferredStatusBarStyle property, which in base class is read-only.

So the idea is to override default UIHostingController to have possibility change that preferredStatusBarStyle value and use custom Environment value so any internal SwiftUI subview can modify that preferred content style.

Here is approach, scratchy, (it is assumed that target Info.plist is configured appropriately)

class LocalStatusBarStyle { // style proxy to be stored in Environment
    fileprivate var getter: () -> UIStatusBarStyle = { .default }
    fileprivate var setter: (UIStatusBarStyle) -> Void = {_ in}

    var currentStyle: UIStatusBarStyle {
        get { self.getter() }
        set { self.setter(newValue) }
    }
}

// Custom Environment key, as it is set once, it can be accessed from anywhere
// of SwiftUI view hierarchy
struct LocalStatusBarStyleKey: EnvironmentKey { 
    static let defaultValue: LocalStatusBarStyle = LocalStatusBarStyle()
}

extension EnvironmentValues { // Environment key path variable
    var localStatusBarStyle: LocalStatusBarStyle {
        get {
            return self[LocalStatusBarStyleKey.self]
        }
    }
}

// Custom hosting controller that update status bar style
class MyHostingController<Content>: UIHostingController<Content> where Content: View {
    private var internalStyle = UIStatusBarStyle.default

    @objc override dynamic open var preferredStatusBarStyle: UIStatusBarStyle {
        get {
            internalStyle
        }
        set {
            internalStyle = newValue
            self.setNeedsStatusBarAppearanceUpdate()
        }
    }

    override init(rootView: Content) {
        super.init(rootView:rootView)

        LocalStatusBarStyleKey.defaultValue.getter = { self.preferredStatusBarStyle }
        LocalStatusBarStyleKey.defaultValue.setter = { self.preferredStatusBarStyle = $0 }
    }

    @objc required dynamic init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }
}

Usage..

1. somewhere in scene delegate

func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
//  ...
  window.rootViewController = MyHostingController(rootView: contentView)

2. somewhere in content view

   struct ContentView: View {
        @Environment(\.localStatusBarStyle) var statusBarStyle
    
        ...
        var body: some View {
            ZStack {
               ....
                NavigationView {
                    NavigationLink(destination:  ...) {
                        ...
                    }
                    .onAppear {
                        self.statusBarStyle.currentStyle = .lightContent
                    }
                    .onDisappear {
                         self.statusBarStyle.currentStyle = .default
                     }
                }
            }
        }
    }

backup