<telerik:RadRichTextEditor x:Name="richTextEditor" Grid.Row="1" TextColor="DarkOrange"
                               BackgroundColor="Black" />

<?xml version="1.0" encoding="utf-8" ?>
<telerik:RadContentView xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
                        xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
                        xmlns:telerik="http://schemas.telerik.com/2022/xaml/maui" 
             x:Class="MAUIThirdPartyControlPOC.RichTextEditorView">


    <Grid RowDefinitions="{OnIdiom Phone='*, Auto'}">

 

            <telerik:RadRichTextEditor x:Name="richTextEditor"
                                   Grid.Row="{OnIdiom Phone=0}"
                                   Source="{Binding Source}">

        </telerik:RadRichTextEditor>
        <telerik:RadRichTextEditorToolbar x:Name="richTextToolbar"
                                          Grid.Row="{OnIdiom Default=1, Phone=1}"
                                          RichTextEditor="{x:Reference richTextEditor}"
                                          Margin="{OnIdiom Phone=0}" />

           </Grid>
</telerik:RadContentView>

using Foundation;
using Microsoft.Maui.Embedding;
using UIKit;
using Telerik.Maui.Controls.Compatibility;
using Telerik.Maui.Controls;
using Microsoft.Maui.Platform;
using Microsoft.Maui.Controls;

namespace MAUIThirdPartyControlPOC;

[Register ("AppDelegate")]
public class AppDelegate : UIApplicationDelegate {
	public override UIWindow? Window {
		get;
		set;
	}

	public static MauiContext _mauiContext;

    public override bool FinishedLaunching (UIApplication application, NSDictionary launchOptions)
	{
		// create a new window instance based on the screen size
		Window = new UIWindow(UIScreen.MainScreen.Bounds);
		
		// create a UIViewController with a single UILabel
		var vc = new UIViewController();
		vc.View.BackgroundColor = UIColor.Orange;

		Window.RootViewController = vc;

		// make the window visible
		Window.MakeKeyAndVisible();


		MauiAppBuilder builder = MauiApp.CreateBuilder();
        builder.UseMauiEmbedding<Microsoft.Maui.Controls.Application>();
		builder.UseTelerik();



        // Register the Window
        builder.Services.Add(new Microsoft.Extensions.DependencyInjection.ServiceDescriptor(typeof(UIWindow), Window));
        MauiApp mauiApp = builder.Build();
        _mauiContext = new MauiContext(mauiApp.Services);

        var richText = new RichTextEditorView();
        var richTextView = richText.ToPlatform(_mauiContext);


        richTextView.TranslatesAutoresizingMaskIntoConstraints = false;

        vc.View!.AddSubview(richTextView);



        NSLayoutConstraint.ActivateConstraints(new[]
		{
			richTextView.WidthAnchor.ConstraintEqualTo(vc.View.WidthAnchor),
            richTextView.HeightAnchor.ConstraintEqualTo(vc.View.HeightAnchor)

        });
        return true;
	}


}

<img src="blob:null/" ..../>