nalu-maui-navigation

---

name: nalu-maui-navigation description: Nalu.Maui.Navigation: type-safe MVVM navigation with Shell, lifecycle events, intents, and guards. Use when setting up navigation, passing parameters, preventing navigation (unsaved changes), custom tab bar, or testing navigation in MAUI.

Nalu.Maui.Navigation

Type-safe navigation on top of Shell: fluent API, scoped disposal, async lifecycle, intents, and guards.

When to use

• Replace Shell string routes with type-based navigation and proper disposal.
• Pass typed data (intents) and get results (awaitable intents).
• Guard navigation (e.g. unsaved changes) and customize tab bar.

Setup

builder.UseNaluNavigation<App>(nav => nav
    .AddPage<MainPageModel, MainPage>()  // AOT: use AddPage for each page
    .WithLeakDetectorState(NavigationLeakDetectorState.EnabledWithDebugger)
);

AOT: Use .AddPage<TPageModel, TPage>() (or with interface) per page; .AddPages() is not AOT/trim-compatible.

Page and ViewModel

• Page: Constructor must take the ViewModel (and optionally other deps); set BindingContext = viewModel.
• ViewModel: Implement INotifyPropertyChanged (e.g. ObservableObject). Register as Scoped; disposed when removed from stack.

Shell

• Use NaluShell; constructor: base(navigationService, typeof(DefaultPage)).
• In XAML: ShellContent with nalu:Navigation.PageType="pages:MainPage".
• In App: MainPage = new AppShell(navigationService). On Android, cache Window in CreateWindow to avoid duplicate Shell.

Navigation API

• Relative: Navigation.Relative().Push<DetailPageModel>(), .Pop(), .Pop().Push<NewPageModel>().
• Absolute: Navigation.Absolute().Root<SettingsPageModel>(), .Root<X>().Add<Y>().
• Execute: await _navigationService.GoToAsync(navigation).

XAML: NavigateCommand with RelativeNavigation and NavigationPop or NavigationSegment Type="pages:DetailPage".

Lifecycle

Implement only what you need. Order: Entering → animation → Appearing → ... → Disappearing → Leaving → animation → Dispose.

Interface	When	Fires multiple times?
IEnteringAware	Before animation	No
IAppearingAware	After animation	Yes (returning from child)
IDisappearingAware	Before leaving	Yes (pushing a child)
ILeavingAware	Before removal	No
IDisposable	After removal	No

Keep OnEnteringAsync fast (<30ms); use IAppearingAware for slow work or the Background Loading Pattern.

Intents

• Pass data: Navigation.Relative().Push<DetailPageModel>().WithIntent(new ContactIntent(42)). Receive in IEnteringAware<ContactIntent> or IAppearingAware<ContactIntent>.
• Get result: Define class MyIntent : AwaitableIntent<TResult>. Navigate with ResolveIntentAsync<PageModel, TResult>(intent). On pushed page: intent.SetResult(value) then GoToAsync(Navigation.Relative().Pop()).

Use record for intents when possible (value equality for tests).

Guards

Implement ILeavingGuard and CanLeaveAsync(); return false to cancel navigation (e.g. after user confirms "Leave without saving?"). Bypass: Navigation.Relative(NavigationBehavior.IgnoreGuards).Pop().

Custom tab bar

Optional: builder.UseNaluTabBar(). Works with standard Shell and NaluShell.

• NaluTabBar: Use the built-in control and style it (bar/tab colors, shapes, blur). Inherit in XAML and set NaluTabBar.UseBlurEffect in static constructor if needed.
• Completely custom bar: Use any view as tab bar; on tab press call NaluTabBar.GoTo(shellSection) (each tab’s BindingContext = corresponding ShellSection). Attach via nalu:NaluShell.TabBarView="{YourCustomTabBar}".

For edge-to-edge and safe area (e.g. content not extending into bottom inset), see Custom TabBarView: edge-to-edge / safe area (root Grid with SafeAreaEdges="None", inner content with SafeAreaEdges="Container").

Full reference: Custom Tab Bar.

Testing

Mock INavigationService (e.g. NSubstitute). Assert with nav.Matches(expectedNav) on the argument passed to GoToAsync. Use record intents for easy equality.

Caveats

• Dispatch navigation from lifecycle events: use IDispatcher.DispatchAsync(() => _navigationService.GoToAsync(...)) to avoid blocking.
• Match cleanup to creation: Constructor ↔ Dispose, Entering ↔ Leaving, Appearing ↔ Disappearing.

Additional context

• Navigation · Lifecycle · Intents · Advanced · Tab Bar · Testing
• Code: Source/Nalu.Maui.Navigation/