Support MainPage in the App constructor (#1419)

* Revert "Fix XamlApp to use CreateWindow for now"

This reverts commit 929cb9b.

* Ensure that the Forms.Init is called early enough

* No slf for vscode

* fix tests

Author: mattleibow

src/Compatibility/Core/src/AppHostBuilderExtensions.cs

@@ -72,93 +72,125 @@ static IAppHostBuilder SetupDefaults(this IAppHostBuilder builder)
 			{
 #if __ANDROID__
 				events.AddAndroid(android => android
-					.OnCreate((a, b) =>
+					.OnApplicationCreating((app) =>
 					{
-						// This just gets Forms Compat bits setup with what it needs
-						// to initialize the first view. MauiContext hasn't been initialized at this point
-						// so we setup one that will look exactly the same just
-						// to make legacy Forms bits happy
+						// This is the initial Init to set up any system services registered by
+						// Forms.Init(). This happens in the Application's OnCreate - before
+						// any UI has appeared.
+						// This creates a dummy MauiContext that wraps the Application.
+
 						var services = MauiApplication.Current.Services;
-						MauiContext mauiContext = new MauiContext(services, a);
-						ActivationState state = new ActivationState(mauiContext, b);
-						Forms.Init(new ActivationState(mauiContext, b), new InitializationOptions() { Flags = InitializationFlags.SkipRenderers });
+						var mauiContext = new MauiContext(services, app);
+						var state = new ActivationState(mauiContext);
+						Forms.Init(state, new InitializationOptions { Flags = InitializationFlags.SkipRenderers });
+
 						GraphicsPlatform.RegisterGlobalService(NativeGraphicsService.Instance);
 					})
-					.OnPostCreate((_, b) =>
+					.OnCreate((activity, bundle) =>
+					{
+						// This is the Init that sets up the first context from the activity.
+						// There is still no official MauiContext since that happens just after this.
+
+						var services = MauiApplication.Current.Services;
+						var mauiContext = new MauiContext(services, activity);
+						var state = new ActivationState(mauiContext, bundle);
+						Forms.Init(state, new InitializationOptions { Flags = InitializationFlags.SkipRenderers });
+					})
+					.OnPostCreate((activity, bundle) =>
 					{
-						// This calls Init again so that the MauiContext that's part of
-						// Forms.Init matches the rest of the maui application
-						var mauiApp = MauiApplication.Current.Application;
-						if (mauiApp.Windows.Count > 0)
+						// This is the final Init that ensures the Forms type is using the same
+						// MauiContext that is part of the rest of the maui application.
+
+						var windows = Application.Current?.Windows;
+						if (windows?.Count > 0)
 						{
-							var window = mauiApp.Windows[0];
-							var mauiContext = window.Handler?.MauiContext ?? window.View.Handler?.MauiContext;
+							var window = windows[0];
+							var mauiContext =
+								window.Handler?.MauiContext ??
+								window.Page?.Handler?.MauiContext;
 
 							if (mauiContext != null)
 							{
-								Forms.Init(new ActivationState(mauiContext, b));
+								var state = new ActivationState(mauiContext, bundle);
+								Forms.Init(state);
 							}
 						}
 					}));
 #elif __IOS__
-				events.AddiOS(iOS =>
-				{
-					iOS.WillFinishLaunching((x, y) =>
+				events.AddiOS(iOS => iOS
+					.WillFinishLaunching((app, options) =>
 					{
-						MauiContext mauiContext = new MauiContext(MauiUIApplicationDelegate.Current.Services, new UIKit.UIWindow());
-						Forms.Init(new ActivationState(mauiContext), new InitializationOptions() { Flags = InitializationFlags.SkipRenderers });
-						return true;
-					});
+						// This is the initial Init to set up any system services registered by
+						// Forms.Init(). This happens before any UI has appeared.
+						// This creates a dummy MauiContext.
 
-					iOS.FinishedLaunching((x,y) =>
+						var services = MauiUIApplicationDelegate.Current.Services;
+						var mauiContext = new MauiContext(services);
+						var state = new ActivationState(mauiContext);
+						Forms.Init(state, new InitializationOptions { Flags = InitializationFlags.SkipRenderers });
+						return true;
+					})
+					.FinishedLaunching((app, options) =>
 					{
-						// This calls Init again so that the MauiContext that's part of
-						// Forms.Init matches the rest of the maui application
-						var mauiApp = MauiUIApplicationDelegate.Current.Application;
+						// This is the final Init that ensures the Forms type is using the same
+						// MauiContext that is part of the rest of the maui application.
 
-						if (mauiApp.Windows.Count > 0)
+						var windows = Application.Current?.Windows;
+						if (windows?.Count > 0)
 						{
-							var window = mauiApp.Windows[0];
-							var mauiContext = window.Handler?.MauiContext ?? window.View.Handler?.MauiContext;
+							var window = windows[0];
+							var mauiContext =
+								window.Handler?.MauiContext ??
+								window.Page?.Handler?.MauiContext;
 
 							if (mauiContext != null)
 							{
-								Forms.Init(new ActivationState(mauiContext));
+								var state = new ActivationState(mauiContext);
+								Forms.Init(state);
 							}
 						}
-						
+
 						GraphicsPlatform.RegisterGlobalService(NativeGraphicsService.Instance);
 
 						return true;
-					});
-				});
+					}));
 #elif WINDOWS
 				events.AddWindows(windows => windows
-					.OnLaunching((_, args) =>
+					.OnLaunching((app, args) =>
 					{
-						// We need to call Forms.Init so the Window and Root Page can new up successfully
-						// The dispatcher that's inside of Forms.Init needs to be setup before the initial 
-						// window and root page start creating
+						// This is the initial Init to set up any system services registered by
+						// Forms.Init(). This happens before any UI has appeared.
+						// This creates a dummy MauiContext.
+						// We need to call this so the Window and Root Page can new up successfully
+						// The dispatcher that's inside of Forms.Init needs to be setup before the initial
+						// window and root page start creating.
 						// Inside OnLaunched we grab the MauiContext that's on the window so we can have the correct
 						// MauiContext inside Forms
-						MauiContext mauiContext = new MauiContext(MauiWinUIApplication.Current.Services, new UI.Xaml.Window());
-						ActivationState state = new ActivationState(mauiContext, args);
+
+						var services = MauiWinUIApplication.Current.Services;
+						var mauiContext = new MauiContext(services);
+						var state = new ActivationState(mauiContext, args);
 						Forms.Init(state, new InitializationOptions() { Flags = InitializationFlags.SkipRenderers });
+
 						GraphicsPlatform.RegisterGlobalService(W2DGraphicsService.Instance);
 					})
-					.OnLaunched((_, args) =>
+					.OnLaunched((app, args) =>
 					{
-						// This calls Init again so that the MauiContext that's part of
-						// Forms.Init matches the rest of the maui application
-						var mauiApp = MauiWinUIApplication.Current.Application;
-						if (mauiApp.Windows.Count > 0)
+						// This is the final Init that ensures the Forms type is using the same
+						// MauiContext that is part of the rest of the maui application.
+
+						var windows = Application.Current?.Windows;
+						if (windows?.Count > 0)
 						{
-							var window = mauiApp.Windows[0];
-							var mauiContext = window.Handler?.MauiContext ?? window.View.Handler?.MauiContext;
+							var window = windows[0];
+							var mauiContext =
+								window.Handler?.MauiContext ??
+								window.Page?.Handler?.MauiContext;
 
 							if (mauiContext != null)
 							{
-								Forms.Init(new ActivationState(mauiContext, args));
+								var state = new ActivationState(mauiContext, args);
+								Forms.Init(state);
 							}
 						}
 					}));

src/Controls/samples/Controls.Sample/XamlApp.xaml.cs

@@ -17,11 +17,8 @@ public XamlApp(IServiceProvider services, ITextService textService)
 
 			Debug.WriteLine($"The .NET Purple color is {Resources["DotNetPurple"]}");
 			Debug.WriteLine($"The injected text service had a message: '{textService.GetText()}'");
-		}
 
-		protected override Window CreateWindow(IActivationState activationState)
-		{
-			return new Window(Services.GetRequiredService<Page>());
+			MainPage = Services.GetRequiredService<Page>();
 		}
 
 		public IServiceProvider Services { get; }

src/Core/src/LifecycleEvents/Android/AndroidLifecycleExtensions.cs

@@ -22,8 +22,11 @@ public LifecycleBuilder(ILifecycleBuilder builder)
 				_builder = builder;
 			}
 
-			public void AddEvent(string eventName, Delegate action) =>
+			public void AddEvent<TDelegate>(string eventName, TDelegate action)
+				where TDelegate : Delegate
+			{
 				_builder.AddEvent(eventName, action);
+			}
 		}
 	}
 }

src/Core/src/LifecycleEvents/ILifecycleBuilder.cs

@@ -4,6 +4,7 @@ namespace Microsoft.Maui.LifecycleEvents
 {
 	public interface ILifecycleBuilder
 	{
-		void AddEvent(string eventName, Delegate action);
+		void AddEvent<TDelegate>(string eventName, TDelegate action)
+			where TDelegate : Delegate;
 	}
 }

src/Core/src/LifecycleEvents/LifecycleEventService.cs

@@ -8,7 +8,8 @@ public class LifecycleEventService : ILifecycleEventService
 	{
 		readonly Dictionary<string, List<Delegate>> _mapper = new Dictionary<string, List<Delegate>>();
 
-		public void AddEvent(string eventName, Delegate action)
+		public void AddEvent<TDelegate>(string eventName, TDelegate action)
+			where TDelegate : Delegate
 		{
 			if (!_mapper.TryGetValue(eventName, out var delegates) && delegates == null)
 				_mapper[eventName] = delegates = new List<Delegate>();

src/Core/src/LifecycleEvents/Windows/WindowsLifecycleExtensions.cs

@@ -22,8 +22,11 @@ public LifecycleBuilder(ILifecycleBuilder builder)
 				_builder = builder;
 			}
 
-			public void AddEvent(string eventName, Delegate action) =>
+			public void AddEvent<TDelegate>(string eventName, TDelegate action)
+				where TDelegate : Delegate
+			{
 				_builder.AddEvent(eventName, action);
+			}
 		}
 	}
 }

src/Core/src/LifecycleEvents/iOS/iOSLifecycleExtensions.cs

@@ -22,8 +22,11 @@ public LifecycleBuilder(ILifecycleBuilder builder)
 				_builder = builder;
 			}
 
-			public void AddEvent(string eventName, Delegate action) =>
+			public void AddEvent<TDelegate>(string eventName, TDelegate action)
+				where TDelegate : Delegate
+			{
 				_builder.AddEvent(eventName, action);
+			}
 		}
 	}
 }

src/Core/src/Platform/Android/MauiAppCompatActivity.cs

@@ -41,19 +41,17 @@ protected override void OnCreate(Bundle? savedInstanceState)
 			if (mauiApp == null)
 				throw new InvalidOperationException($"The {nameof(IServiceProvider)} instance was not found.");
 
-			MauiContext mauiContext;
-			IWindow window;
+			var mauiContext = new MauiContext(services, this);
 
 			// TODO Fix once we have multiple windows
+			IWindow window;
 			if (mauiApp.Windows.Count > 0)
 			{
 				window = mauiApp.Windows[0];
-				mauiContext = new MauiContext(services, this);
 			}
 			else
 			{
-				mauiContext = new MauiContext(services, this);
-				ActivationState state = new ActivationState(mauiContext, savedInstanceState);
+				var state = new ActivationState(mauiContext, savedInstanceState);
 				window = mauiApp.CreateWindow(state);
 			}
 

src/Core/src/Platform/MauiContext.Android.cs

@@ -1,22 +1,22 @@
 using System;
-using System.Collections.Generic;
-using System.Text;
 using Android.Content;
-using Microsoft.Extensions.DependencyInjection;
-
 
 namespace Microsoft.Maui
 {
 	public partial class MauiContext
 	{
 		readonly WeakReference<Context>? _context;
-		public MauiContext(IServiceProvider services, Context context) : this(services)
+
+		public MauiContext(IServiceProvider services, Context context)
+			: this(services)
 		{
 			_context = new WeakReference<Context>(context ?? throw new ArgumentNullException(nameof(context)));
 		}
 
-		public MauiContext(Context context) : this()
+		public MauiContext(Context context)
+			: this()
 		{
+			_context = new WeakReference<Context>(context ?? throw new ArgumentNullException(nameof(context)));
 		}
 
 		public Context? Context
@@ -26,13 +26,7 @@ public Context? Context
 				if (_context == null)
 					return null;
 
-				Context? context;
-				if (_context.TryGetTarget(out context))
-				{
-					return context;
-				}
-
-				return null;
+				return _context.TryGetTarget(out Context? context) ? context : null;
 			}
 		}
 	}

src/Core/src/Platform/MauiContext.Windows.cs

@@ -1,20 +1,15 @@
 using System;
-using System.Collections.Generic;
-using System.Text;
 
 namespace Microsoft.Maui
 {
 	public partial class MauiContext
 	{
-		public MauiContext(IServiceProvider services, UI.Xaml.Window window) : this(services)
+		public MauiContext(IServiceProvider services, UI.Xaml.Window window)
+			: this(services)
 		{
 			Window = window ?? throw new ArgumentNullException(nameof(window));
 		}
 
-		public UI.Xaml.Window? Window
-		{
-			get;
-			private set;
-		}
+		public UI.Xaml.Window? Window { get; private set; }
 	}
-}
+}