How to detect when watchOS application becomes active?

Question

I'm using watchOS 7.0 and SwiftUI. My view listens to NSExtensionHostDidBecomeActive notification:

.onReceive(NotificationCenter.default.publisher(for: .NSExtensionHostDidBecomeActive)) { _ in
    NSLog("Foreground")
    viewModel.loadData()
}

However, it is not called.

Answer 1

I solved this issue by using WKExtensionDelegate and my own notifications.

@main
struct ExtensionApp: App {
    @WKExtensionDelegateAdaptor(ExtensionDelegate.self) var appDelegate

    @SceneBuilder var body: some Scene {
        WindowGroup {
            NavigationView {
                MainView()
            }
        }
    }
}

import WatchKit

final class ExtensionDelegate: NSObject, ObservableObject, WKExtensionDelegate {
    func applicationDidFinishLaunching() {
        NSLog("App launched")
    }

    func applicationDidBecomeActive() {
        NSLog("App activated")
        NotificationCenter.default.post(name: .appActivated, object: nil)
    }

    func applicationDidEnterBackground() {
        NSLog("App deactivated")
        NotificationCenter.default.post(name: .appDeactivated, object: nil)
    }
}

import Foundation

extension Notification.Name {
    static let appActivated = Notification.Name("app.activated")
    static let appDeactivated = Notification.Name("app.deactivated")
}

then I was able to listen to these events in my SwiftUI view:

.onReceive(NotificationCenter.default.publisher(for: .appActivated)) { _ in
    viewModel.appActivated()
}
.onReceive(NotificationCenter.default.publisher(for: .appDeactivated)) { _ in
    viewModel.appDeactivated()
}