.NET MAUI Application Lifecycle: Comprehensive Breakdown

The MAUI application lifecycle involves several stages from launch to termination, with platform-specific behaviors on iOS and Android. Here's a detailed explanation of each phase:

1. Application Startup

Common MAUI Initialization

1. Platform Bootstrapping:

   • Native OS launches the executable

   • Platform-specific runtime initializes (Mono for Android, .NET for iOS)

2. MauiProgram Execution:

   csharp

   public static MauiApp CreateMauiApp()
   {
       var builder = MauiApp.CreateBuilder();
       builder.UseMauiApp<App>();
       // Configure services, fonts, etc.
       return builder.Build();
   }

   • Dependency injection container configured

   • Application services registered

3. App Class Instantiation:

   • App.xaml.cs constructor executes

   • Main page set via MainPage = new MainPage();

Platform-Specific Startup

Android:

1. MainActivity (derives from MauiAppCompatActivity) launches

2. OnCreate() called:

   java

   protected override void OnCreate(Bundle savedInstanceState)
   {
       base.OnCreate(savedInstanceState);
       // MAUI initialization happens here
   }

3. XAML handler system initializes

iOS:

1. UIApplicationMain entry point executes

2. MauiUIApplicationDelegate methods called:

   csharp

   [Register("AppDelegate")]
   public class AppDelegate : MauiUIApplicationDelegate
   {
       protected override MauiApp CreateMauiApp() => MauiProgram.CreateMauiApp();
   }

3. Root view controller initialized

2. Page Lifecycle Events

MAUI Page Events (Cross-Platform)

1. NavigatingTo (called before page appears)

2. NavigatedTo (after page appears)

3. NavigatingFrom (before page disappears)

4. NavigatedFrom (after page disappears)

csharp

protected override void OnAppearing()
{
    base.OnAppearing();
    // Equivalent to NavigatedTo
    // Start animations, load data
}

protected override void OnDisappearing()
{
    base.OnDisappearing();
    // Equivalent to NavigatedFrom
    // Pause operations, save state
}

3. Application State Transitions

Foreground/Background States

Common Events:

• Application.Current.PageAppearing

• Application.Current.PageDisappearing

Android Specifics:

1. Resume (OnResume()):

   • App returns to foreground

   • MAUI triggers OnResume event

2. Pause (OnPause()):

   • App going to background

   • MAUI triggers OnSleep event

iOS Specifics:

1. Active (OnActivated):

   • App enters foreground

   • MAUI triggers OnResume

2. Background (DidEnterBackground):

   • App enters background

   • MAUI triggers OnSleep

4. Detailed Lifecycle Sequence

Cold Start Scenario

1. Platform launches process

2. MauiProgram.CreateMauiApp() executes

3. DI container built

4. App constructor runs

5. MainPage created

6. Platform-specific window created

7. OnStart triggered (Android only)

8. OnAppearing for initial page

9. UI becomes interactive

Background to Foreground

1. OS resumes app process

2. OnResume triggered (cross-platform)

3. Current page's OnAppearing called

4. UI updates resume

Foreground to Background

1. User navigates away from app

2. Current page's OnDisappearing called

3. OnSleep triggered (cross-platform)

4. App may enter suspended state

5. Platform-Specific Lifecycle Details

Android Lifecycle Mapping

Android Activity	MAUI Equivalent
OnCreate()	App constructor
OnStart()	OnStart
OnResume()	OnResume
OnPause()	OnSleep
OnStop()	(Part of Sleep)
OnDestroy()	OnDestroy

Key Notes:

• OnSleep combines Android's OnPause and OnStop

• OnResume matches Android's OnResume

iOS Lifecycle Mapping

iOS Event	MAUI Equivalent
FinishedLaunching	App startup
OnActivated	OnResume
DidEnterBackground	OnSleep
WillTerminate	OnDestroy

Key Notes:

• iOS uses scene-based lifecycle in modern apps

• MAUI abstracts scene management

6. Lifecycle Customization

Handling Events in App.xaml.cs

csharp

public partial class App : Application
{
    public App()
    {
        InitializeComponent();
        
        this.Startup += OnStartup;
        this.Sleep += OnAppSleep;
        this.Resume += OnAppResume;
    }
    
    private void OnAppSleep(object sender, EventArgs e)
    {
        // Save state, pause network operations
    }
    
    private void OnAppResume(object sender, EventArgs e)
    {
        // Refresh data, restart services
    }
}

Page-Level Management

csharp

public partial class MainPage : ContentPage
{
    protected override void OnAppearing()
    {
        base.OnAppearing();
        StartDataRefresh();
    }
    
    protected override void OnDisappearing()
    {
        base.OnDisappearing();
        StopDataRefresh();
    }
    
    protected override void OnBindingContextChanged()
    {
        base.OnBindingContextChanged();
        // Handle data context changes
    }
}

7. Special Scenarios

State Preservation

• Android: Bundle saved in OnSaveInstanceState

• iOS: State restoration methods

• MAUI provides IPersistedState interface

Memory Pressure

• Both platforms may terminate backgrounded apps

• MAUI provides MemoryManager to monitor pressure

Multi-Window (Android)

• Each window maintains separate lifecycle

• Handled via OnConfigurationChanged

8. Shutdown Sequence

Normal Termination

1. OnDisappearing for current page

2. OnSleep triggered

3. OnDestroy (Android) or WillTerminate (iOS)

4. Process terminated

Abnormal Termination

• Crash or force-stop bypasses normal lifecycle

• MAUI provides crash reporting hooks

Understanding this complete lifecycle helps properly manage resources, maintain state, and provide smooth user experiences across all platform states.