Added embedding extensions

[Clancey]

Description of Change

This adds a new Api that will allow us to control registration for Maui Native embedding.

Issues Fixed

Fixes (partially) #1718

Usage:
Maui Embedding.md

[Clancey]

Maui Embedding

So you have a Net 6.0 App (iOS MacOS, Android, or Windows) , and you want to add a few Maui Screens. No Problem!

Setup

First you need to add UseMaui to the CSProj

  <PropertyGroup>
	  <UseMaui>true</UseMaui>
  </PropertyGroup>

iOS/Mac

First create a MauiContext. This is best done in your AppDelegate

    	public static MauiContext MauiContext;
		public override bool FinishedLaunching(UIApplication app, NSDictionary options)
		{
			///Your normal iOS registration
			
			//Setup MauiBits
			var builder = MauiApp.CreateBuilder();
			
			//Add Maui Controls
			builder.UseMauiEmbedded();
			
			//Using comet?
			//builder.UseComet();
			
			//iOS/Mac need to register the Window
			
			builder.Services.Add( new Microsoft.Extensions.DependencyInjection.ServiceDescriptor(typeof(UIKit.UIWindow),window));
			    
			var mauiApp = builder.Build();
			
			//Create and save a Maui Context. This is needed for creating Platform UI
			mauiContext = new MauiContext(mauiApp.Services);
			return true;
		}

Now you can create and use a MauiView!

		//Create a Maui Page
		var myMauiPage = new MyMauiPage();
		
		//Turn the Maui page into an Android View
		UIView view = myMauiPage.ToPlatform(mauiContext);

Android

using Android.App;
using Android.OS;
using Microsoft.Maui.Platform;
using Microsoft.Maui.Embedding;


[Activity(Label = "@string/app_name", MainLauncher = true)]
public class MainActivity : Activity
{
	MauiContext mauiContext;
	protected override void OnCreate(Bundle? savedInstanceState)
	{
		base.OnCreate(savedInstanceState);
		
		//Setup MauiBits
		var builder = MauiApp.CreateBuilder();
		
		//Add Maui Controls
		builder.UseMauiEmbedded();
		
		//Using comet?
		//builder.UseComet();
		    
		var mauiApp = builder.Build();
		
		//Create and save a Maui Context. This is needed for creating Platform UI
		mauiContext = new MauiContext(mauiApp.Services,this);
		
		//Create a Maui Page
		var myMauiPage = new MyMauiPage();
		
		//Turn the Maui page into an Android View
		var view = myMauiPage.ToPlatform(mauiContext);
		
		//Use the Android View
		SetContentView(view);
	}
}

[mattleibow]

Maybe you can make use of the extensions in MauiContextExtensions to capture and store the platform app and window for use in other places:

• MakeApplicationScope
• MakeWindowScope

For example, it could be possible to make a new extension method for MauiApp:

// this can be stored in a static location
var mauiEmbeddedApp = MauiApp
    .CreateBuilder()
    .UseMauiEmbedded()
    .Build()
    .ToEmbedded(); // new method

// this runs on each window or activity
var platformWindow = ... // Window on iOS, this on Android, this on WinUI
var mauiContext = mauiEmbeddedApp.CreateWindowContext(platformWindow);

// back to normal things
var page = new ContentPage {
    new Label { Text = "w00t!" }
};
var platformView = page.ToPlatform(mauiContext);

The new extension method just returns a wrapped MauiApp that holds the context:

static class EmbeddedExtensions {
    public static MauiEmbeddedApp ToEmbedded(this MauiApp mauiApp) {
        var platformApp = UIApplication.SharedApplication;
        var platformApp = Android.App.Application.Context as Android.App.Application;
        var platformApp = UI.Xaml.Application.Current;

        // create scopes to make sure the platform app is added (ie: UIAppDelegate is in the services)
        var mauiContext = new MauiContext(mauiApp.Services, platformApp);
        var appContext = mauiContext.MakeAppScope(platformApp);

        var embedded = new MauiEmbeddedApp(mauiApp, appContext);
        return embedded;
    }

    public static MauiContext CreateWindowContext(this MauiEmbeddedApp mauiApp, PlatformWindow platformWindow) {
        // create scopes to make sure the platform window is added (ie: UIWindow is in the services)
        var windowContext = mauiApp.MauiApplicationContext.MakeWindowScope(platformWindow);
        return windowContext;
    }
}

class MauiEmbeddedApp : IDisposable {
    internal MauiEmbeddedApp(MauiApp mauiApp, MauiContext appContext);
    public MauiApp { get; }
    public MauiContext MauiApplicationContext { get; }
    public IServiceProvider Services => MauiApp.Services;
    public IConfiguration Configuration => MauiApp.Configuration;
}

[Redth]

Moved @mattleibow 's comments to the original issue for tracking in future work.

[SparkieLabs]

I tried adding UseMaui to a WinUI project and got the following errors:

..\WinUIApp\Microsoft.Maui.Controls.SourceGen\Microsoft.Maui.Controls.SourceGen.CodeBehindGenerator\App.xaml.sg.cs(20,16,20,35): error CS0111: Type 'App' already defines a member called 'InitializeComponent' with the same parameter types
..\WinUIApp\Microsoft.Maui.Controls.SourceGen\Microsoft.Maui.Controls.SourceGen.CodeBehindGenerator\MainWindow.xaml.sg.cs(24,16,24,35): error CS0111: Type 'MainWindow' already defines a member called 'InitializeComponent' with the same parameter types

It looks like both Maui and WinUI are source generating from the xaml files. Is there a way to disable the Maui xaml source generator?

[mattleibow]

@sparkie108 could you open a new issue with you problem? I think there may be some extra steps, but I think the discussion is going to be lost here.

[SparkieLabs]

I have created a WinUI example that now works here:

https://github.com/sparkie108/MauiWinUIEmbedding

[devjama]

Is there (or will there be) a possibility to embed MAUI to UWP application?