I'm dealing with my login screen. For that, I've defined an @AppStorage property. On change of scenePhase, I toggle it to false, and call FaceIDAuthentication method when it comes to active:

@main
struct MyApp: App {
@AppStorage("appBlocked") private var appBlocked = false
@Environment(\.scenePhase) var phase
...
MainView()
   .onChange(of: phase) { (newPhase) in
                    switch newPhase {
                    case .active : print("App is active")
                        //**
                        if appBlocked {
                                faceIdAuthentication()
                        }
                    case .inactive : print("App is inactive")
                    case .background : print("App is on background")
                            appBlocked = true
                    default: print("default")
                    }
                }

On my MainView (second on the hiearchy), I condition all shown content to this value:

struct MainView: View {

@AppStorage("appBlocked") private var appBlocked = false

var body: some View {

        if appBlocked {
            LoginView()
                .transition(.opacity)
        } else {

        //App regular views...

I change this value on Login view (password, just in case FaceId fails, or is not on) with:

if inputPassword == password {
       withAnimation {
             appBlocked = false
        }
     } else {
incorrectPassword = true
     }

And on FaceIdAthentication with:

if sucess {
     withAnimation {
           appBlocked = false
      }

Both login methods (password and FaceId) work like a charm. But animations don't: no animation (opacity of MainView, or the other two on changing the value) at all is used when "unpresenting" LoginView.

Is this the correct way of doing so? Explained here: https://www.hackingwithswift.com/quick-start/swiftui/how-to-add-and-remove-views-with-a-transition

Is it correct monitoring @AppStore (UserDefaults) for animations to fire? Have I to add any aditional modifier to my LoginView() on MainView call, maybe?

An idea..I don't know if it would work.. but what if you change

if appBlocked {
            LoginView()
                .transition(.opacity)
        }

to

.animation(.easeInOut, value: appBlocked )

The animation will be triggerred once the the appBlocked value will change..

Thanks, @Bnerd. Efectively: passing the value to be directly monitored... But still not working.

Could it be related to the fact that I use this way as well on @main view? must animation be there? (marked whith ** above)? But this case is only related to FaceID call. It must work with password, not being used then.

As per my understanding the .animation goes to what you want to animate. Login -> Main .animaiton goes to Main Main -> Login .animaiton goes to Login

Give it a try

I've moved the method from MainView...

var body: some View {
  if appBlocked {
     LoginView()
        .animation(.easeInOut, value: appBlocked)
} else {
    //General view...

...to @main App struct:

WindowGroup {
   if appBlocked {
       LoginView()
           .animation(.easeInOut, value: appBlocked)
    } else {
       MainView()

Thus, one level higher, to the top of app hiearchy. Thinking with your idea that, as appBlocked toggle is received before on "top" @main app structure, I cannot see it on "lower" MainView().

But still no animation. Any further ideas?