MainActivity.cs

using System;

using Android.App;
using Android.Content.PM;
using Android.Runtime;
using Android.Views;
using Android.Widget;
using Android.OS;
using DevExpress.XamarinForms.Scheduler.Android;
using DevExpress.XamarinForms.Scheduler;

namespace CustomMonthViewProviders.Droid {
    [Activity(Label = "CustomMonthViewProviders", Icon = "@mipmap/icon", Theme = "@style/MainTheme", MainLauncher = true, ConfigurationChanges = ConfigChanges.ScreenSize | ConfigChanges.Orientation)]
    public class MainActivity : global::Xamarin.Forms.Platform.Android.FormsAppCompatActivity {
        protected override void OnCreate(Bundle savedInstanceState) {
            TabLayoutResource = Resource.Layout.Tabbar;
            ToolbarResource = Resource.Layout.Toolbar;

            base.OnCreate(savedInstanceState);

            Xamarin.Essentials.Platform.Init(this, savedInstanceState);
            global::Xamarin.Forms.Forms.Init(this, savedInstanceState);

            MonthViewProviderService.RegisterViewProviderService(new CustomMonthViewProviderService());

            LoadApplication(new App());
        }

        public override void OnRequestPermissionsResult(int requestCode, string[] permissions, [GeneratedEnum] Android.Content.PM.Permission[] grantResults) {
            Xamarin.Essentials.Platform.OnRequestPermissionsResult(requestCode, permissions, grantResults);
            base.OnRequestPermissionsResult(requestCode, permissions, grantResults);
        }
    }

    public class CustomMonthViewProviderService : MonthViewProviderService {
        public override IViewProvider CreateCellViewProvider(MonthView monthView) {
            return new CustomCellViewProvider();
        }

        public override IViewProvider CreateAppointmentViewProvider(MonthView monthView) {
            return new CustomAppointmentViewProvider();
        }
    }
}