Try to migrate from Xamarin to MAUI

On Xamarin i have simple code for fullscreen loader

Xamarin code

Interface on root project

namespace SkeletonApp.View.Loader
{
    public interface ILodingPageService
    {
        void InitLoadingPage(Xamarin.Forms.ContentPage loadingIndicatorPage = null);

        void ShowLoadingPage();

        void HideLoadingPage();
    }
}

Implementation on Android sub-project

using System;
using Android.App;
using Android.Graphics.Drawables;
using Android.Views;
using Plugin.CurrentActivity;
using Xamarin.Forms;
using Xamarin.Forms.Platform.Android;
using SkeletonApp.Droid;
using XFPlatform = Xamarin.Forms.Platform.Android.Platform;
using SkeletonApp.View.Loader;

[assembly: Xamarin.Forms.Dependency(typeof(LodingPageServiceDroid))]
namespace SkeletonApp.Droid {
    public class LodingPageServiceDroid : ILodingPageService {
        private Android.Views.View _nativeView;
        private Dialog _dialog;
        private bool _isInitialized;

        public void InitLoadingPage(ContentPage loadingIndicatorPage) {
            // check if the page parameter is available
            if (loadingIndicatorPage != null) {
                // build the loading page with native base
                loadingIndicatorPage.Parent = Xamarin.Forms.Application.Current.MainPage;

                loadingIndicatorPage.Layout(new Rectangle(0, 0,
                    Xamarin.Forms.Application.Current.MainPage.Width,
                    Xamarin.Forms.Application.Current.MainPage.Height));

                var renderer = loadingIndicatorPage.GetOrCreateRenderer();

                _nativeView = renderer.View;

                _dialog = new Dialog(CrossCurrentActivity.Current.Activity);
                _dialog.RequestWindowFeature((int)WindowFeatures.NoTitle);
                _dialog.SetCancelable(false);
                _dialog.SetContentView(_nativeView);
                Window window = _dialog.Window;
                window.SetLayout(ViewGroup.LayoutParams.MatchParent, ViewGroup.LayoutParams.MatchParent);
                window.ClearFlags(WindowManagerFlags.DimBehind);
                window.SetBackgroundDrawable(new ColorDrawable(Android.Graphics.Color.Transparent));

                _isInitialized = true;
            }
        }

        public void ShowLoadingPage() {
            // check if the user has set the page or not
            if (_isInitialized == false) {
                InitLoadingPage(new DefaultLoader()); // set the default page
            }
            _dialog.Show();
        }

        private void XamFormsPage_Appearing(object sender, EventArgs e)
        {
            var animation = new Animation(callback: d => ((ContentPage)sender).Content.Rotation = d,
                                          start: ((ContentPage)sender).Content.Rotation,
                                          end: ((ContentPage)sender).Content.Rotation + 360,
                                          easing: Easing.Linear);
            animation.Commit(((ContentPage)sender).Content, "RotationLoopAnimation", 16, 800, null, null, () => true);
        }

        public void HideLoadingPage()  {
            _dialog.Hide();
        }
    }

    internal static class PlatformExtension {
        public static IVisualElementRenderer GetOrCreateRenderer(this VisualElement bindable) {
            var renderer = XFPlatform.GetRenderer(bindable);
            if (renderer == null)
            {
                renderer = XFPlatform.CreateRendererWithContext(bindable, CrossCurrentActivity.Current.Activity);
                XFPlatform.SetRenderer(bindable, renderer);
            }
            return renderer;
        }
    }
}

Call loader on root project

// Show loader
DependencyService.Get<ILodingPageService>().ShowLoadingPage();
// Hide loader
DependencyService.Get<ILodingPageService>().HideLoadingPage();

And this works fine

Try to migrate on MAUI

Interface – same

Implementation change to

using Android.App;
using Android.Graphics.Drawables;
using AndroidViews = Android.Views;
using Microsoft.Maui.Controls.Compatibility.Platform.Android;
using SkeletonAppMAUI.Tools.View.Loader;
using AndroidPlatform = Microsoft.Maui.Controls.Compatibility.Platform.Android.Platform;
using AndroidColor = Android.Graphics.Color;

[assembly: Microsoft.Maui.Controls.Dependency(typeof(SkeletonAppMAUI.Platforms.Android.LodingPageServiceDroid))]
namespace SkeletonAppMAUI.Platforms.Android {
    public class LodingPageServiceDroid : ILodingPageService {
        private AndroidViews.View _nativeView;

        private Dialog _dialog;

        private bool _isInitialized;

        public void InitLoadingPage(ContentPage loadingIndicatorPage) {
            // check if the page parameter is available
            if (loadingIndicatorPage != null) {
                // build the loading page with native base
                loadingIndicatorPage.Parent = Microsoft.Maui.Controls.Application.Current.MainPage;

                loadingIndicatorPage.Layout(new Rect(0, 0,
                    Microsoft.Maui.Controls.Application.Current.MainPage.Width,
                    Microsoft.Maui.Controls.Application.Current.MainPage.Height));

                var renderer = loadingIndicatorPage.GetOrCreateRenderer();

                _nativeView = renderer.View;
                
                _dialog = new Dialog(Microsoft.Maui.ApplicationModel.Platform.CurrentActivity);
                _dialog.RequestWindowFeature((int)AndroidViews.WindowFeatures.NoTitle);
                _dialog.SetCancelable(false);
                _dialog.SetContentView(_nativeView);
                AndroidViews.Window window = _dialog.Window;
                window.SetLayout(AndroidViews.ViewGroup.LayoutParams.MatchParent, AndroidViews.ViewGroup.LayoutParams.MatchParent);
                window.ClearFlags(AndroidViews.WindowManagerFlags.DimBehind);
                window.SetBackgroundDrawable(new ColorDrawable(AndroidColor.Transparent));
                
                _isInitialized = true;
            }
        }

        public void ShowLoadingPage() {
            // check if the user has set the page or not
            if (_isInitialized == false) {
                InitLoadingPage(new DefaultLoader()); // set the default page
            }

            // showing the native loading page
            _dialog.Show();
        }

        private void XamFormsPage_Appearing(object sender, EventArgs e) {
            var animation = new Animation(callback: d => ((ContentPage)sender).Content.Rotation = d,
                                          start: ((ContentPage)sender).Content.Rotation,
                                          end: ((ContentPage)sender).Content.Rotation + 360,
                                          easing: Easing.Linear);
            animation.Commit(((ContentPage)sender).Content, "RotationLoopAnimation", 16, 800, null, null, () => true);
        }

        public void HideLoadingPage()  {
            // Hide the page
            _dialog.Hide();
        }
    }

    internal static class PlatformExtension {
        public static IVisualElementRenderer GetOrCreateRenderer(this VisualElement bindable) {
            var renderer = AndroidPlatform.GetRenderer(bindable);
            if (renderer == null)
            {
                renderer = AndroidPlatform.CreateRendererWithContext(bindable, Microsoft.Maui.ApplicationModel.Platform.CurrentActivity);
                AndroidPlatform.SetRenderer(bindable, renderer);
            }
            return renderer;
        }
    }
}

And when i try to show loader (DependencyService.Get<ILodingPageService>().ShowLoadingPage();) i got fatal about context is empty

Forms.MauiContext.Handlers cannot be null here

For Xamarin I saved the context using the Nuget package Plugin.CurrentActivity in Android Application class, in MAUI it works out of the box using Microsoft.Maui.ApplicationModel.Platform.CurrentActivity (as I understand).

Or did I misunderstand the MAUI concept about getting the context in the target platform?

Xamarin code based by this github repo