macOS SwiftUI中如何在视图外部打开新窗口？

在SwiftUI视图内部，我们可以通过@Environment(\.openWindow)轻松打开指定ID的窗口，但如果在视图外部（比如ObservableObject类中的热键监听器）直接使用@Environment，编译器会抛出警告：

Accessing Environment<OpenURLAction>'s value outside of being installed on a View. This will always read the default value and will not update.

这是因为Environment值仅能在SwiftUI的View层级结构内正常工作，视图外部无法正确获取其有效实例。以下是几种可行的解决方案：

方案一：将环境对象注入到ObservableObject中 #

不要在ObservableObject内部声明@Environment，而是通过初始化参数或后续赋值的方式，从View层级传递有效的OpenWindowAction实例。

1. 修改AppState类，移除@Environment，改为接收外部传入的OpenWindowAction：

@MainActor
final class AppState: ObservableObject {
    private var openWindow: OpenWindowAction?

    init() {
        KeyboardShortcuts.onKeyDown(for: .doubleClick) { [weak self] in
            self?.openWindow?(id: "the-window")
        }
    }

    // 提供方法用于注入OpenWindowAction
    func setOpenWindow(_ action: OpenWindowAction) {
        self.openWindow = action
    }
}

2. 在App结构体的View层级中获取OpenWindowAction并注入到AppState：

@main
struct MyApp: App {
    @StateObject private var appState = AppState()

    var body: some Scene {
        WindowGroup(id: "main") {
            ContentView()
                .environmentObject(appState)
                .onAppear {
                    // 从当前环境中获取OpenWindowAction并注入
                    let openWindow = Environment(\.openWindow).wrappedValue
                    appState.setOpenWindow(openWindow)
                }
        }
        WindowGroup(id: "the-window") {
            Text("新窗口内容")
        }
    }
}

方案二：直接使用AppKit API（macOS专属） #

如果你的应用仅针对macOS，可以直接通过NSApplication的API来操作窗口，绕开SwiftUI的环境限制：

@MainActor
final class AppState: ObservableObject {
    init() {
        KeyboardShortcuts.onKeyDown(for: .doubleClick) {
            let windowID = "the-window"
            let app = NSApplication.shared

            // 先尝试查找已存在的窗口并激活
            for scene in app.connectedScenes {
                guard let windowScene = scene as? NSWindowScene else { continue }
                if let targetWindow = windowScene.windows.first(where: {
                    $0.identifier?.rawValue == windowID
                }) {
                    targetWindow.makeKeyAndOrderFront(nil)
                    return
                }
            }

            // 如果窗口不存在，创建新窗口并添加到当前场景
            guard let activeScene = app.connectedScenes.first as? NSWindowScene else { return }
            let newWindow = NSWindow(
                contentRect: NSRect(x: 200, y: 200, width: 400, height: 300),
                styleMask: [.titled, .closable, .miniaturizable, .resizable],
                backing: .buffered,
                defer: false
            )
            newWindow.identifier = NSUserInterfaceItemIdentifier(windowID)
            newWindow.contentView = NSHostingView(rootView: Text("新窗口内容"))
            activeScene.addWindow(newWindow)
            newWindow.makeKeyAndOrderFront(nil)
        }
    }
}

方案三：通过通知中心解耦 #

利用NotificationCenter在视图外部发送通知，在View层级内监听通知并调用openWindow，实现解耦：

1. 在AppState中发送通知：

@MainActor
final class AppState: ObservableObject {
    init() {
        KeyboardShortcuts.onKeyDown(for: .doubleClick) {
            NotificationCenter.default.post(
                name: NSNotification.Name("OpenTargetWindow"),
                object: nil
            )
        }
    }
}

2. 在任意View中监听通知并执行窗口打开操作：

struct ContentView: View {
    @Environment(\.openWindow) var openWindow
    @EnvironmentObject var appState: AppState

    var body: some View {
        Text("主视图")
            .onReceive(NotificationCenter.default.publisher(for: NSNotification.Name("OpenTargetWindow"))) { _ in
                openWindow(id: "the-window")
            }
    }
}

内容的提问来源于stack exchange，提问作者gcstr