.NET MAUI App Lifecycle

App lifecycle across platforms in .NET MAUI, since it’s slightly different depending on whether you’re running on Android, iOS, Windows, or macOS.

App Lifecycle in MAUI

1. Startup

Android → MainActivity.OnCreate() initializes the app, loads MauiProgram.CreateMauiApp().

iOS/macOS (Catalyst) → AppDelegate.FinishedLaunching() starts the app and loads the MAUI app.

Windows → WinUIApp.OnLaunched() initializes the app.

All platforms eventually call into MauiProgram.CreateMauiApp() which sets up services, resources, and the App class.

2. Running State

The app is active and visible.

Application.OnStart() is triggered when the app first runs.

Pages and Shell lifecycle events (OnAppearing, OnNavigated) occur during navigation.

3. Background / Sleep

Android → OnPause() is called when the app goes into the background.

iOS/macOS → OnResignActivation() or DidEnterBackground() is triggered.

Windows → OnSuspending() is called when the app is minimized or suspended.

In MAUI, this maps to Application.OnSleep().

4. Resume

Android → OnResume() when returning from background.

iOS/macOS → WillEnterForeground() or OnActivated().

Windows → OnResuming().

In MAUI, this maps to Application.OnResume().

5. Exit / Termination

Android → OnDestroy() when the activity is destroyed.

iOS/macOS → WillTerminate() when the app is killed.

Windows → OnSuspending() may be followed by termination.

In MAUI, this maps to Application.OnStop().

Summary Table

Lifecycle Stage	Android	iOS/macOS	Windows	MAUI Abstraction
Start	OnCreate	FinishedLaunching	OnLaunched	OnStart
Sleep	OnPause	DidEnterBackground	OnSuspending	OnSleep
Resume	OnResume	WillEnterForeground	OnResuming	OnResume
Exit	OnDestroy	WillTerminate	Termination after suspend	OnStop

Best Practices

• Use OnStart, OnSleep, and OnResume in App.xaml.cs for cross-platform lifecycle handling.
• Keep platform-specific logic in Handlers or platform-specific projects.
• Avoid heavy work in lifecycle methods; offload to background services if possible.
• Always save state in OnSleep to prevent data loss.

.NET MAUI App vs Shell Lifecycle

App Lifecycle (platform-level) and the Shell Lifecycle (navigation/UI-level) fit together in .NET MAUI:

App Lifecycle vs Shell Lifecycle

App Lifecycle (Platform-Level)

This is about the application process itself across Android, iOS/macOS, and Windows:

• OnStart → App launches (MainActivity.OnCreate, AppDelegate.FinishedLaunching, WinUIApp.OnLaunched).
• OnSleep → App goes into background (OnPause, DidEnterBackground, OnSuspending).
• OnResume → App comes back to foreground (OnResume, WillEnterForeground, OnResuming).
• OnStop / Terminate → App is closed (OnDestroy, WillTerminate, termination after suspend).

Shell Lifecycle (Navigation/UI-Level)

This is about the user interface and navigation container:

• Shell Initialization → Routes registered, Shell object created.
• OnAppearing → Shell or page becomes visible.
• OnNavigating → Before navigation occurs (can cancel).
• OnNavigated → After navigation completes.
• OnDisappearing → Shell or page hidden or disposed.

Comparison Table

Stage	App Lifecycle (Platform)	Shell Lifecycle (UI)
Launch	OnStart	Shell constructor + route registration
Visible	Running state	OnAppearing (Shell/page)
Background	OnSleep	Page disappears (OnDisappearing)
Resume	OnResume	OnAppearing again
Navigation	N/A (platform doesn’t handle this)	OnNavigating / OnNavigated
Exit	OnStop / Terminate	Shell disposed

Key Insight

Think of it like two layers working together:

• The App lifecycle is the outer shell controlled by the operating system (start, sleep, resume, exit).
• The Shell lifecycle is the inner navigation flow controlled by MAUI’s Shell (appearing, navigating, disappearing).