Setting mainpage after login results in blank page

Hi Guys!

It's been a while since I've been here, but I finally found the time to continue working and improving my app. One of these improvements is implementing an Identityserver instance to manage the authentication.

Using the following topics I got this working;

• https://www.scottbrady91.com/Identity-Server/Getting-Started-with-IdentityServer-4
• https://sinclairinat0r.com/2018/12/09/secure-data-access-with-identityserver4-and-xamarin-forms
• https://ngohungphuc.wordpress.com/2018/12/11/identity-server-4-with-asp-net-core-2-2/

Since my login procedure is a little bit different from what the examples are showing, I implemented a page with a Login and Registration button. The login works, but after Identityserver redirects me to my app and all the account information is stored, I'm getting a blank page. When I restart my app I immediately get the MainPage which I want to see, because I have a valid account stored.

My SignIn page shows a login and registration button. The loginbutton triggers an oAuthLoginPage which uses a PageRenderer. The code looks like this for my oAuthLoginpage, it's just a C# class;

public class OAuthLoginPage : ContentPage
    {
        public static event EventHandler LoginSucceeded;
        public static event EventHandler LoginCancelled;

        public static void LoginSuccess(object sender)
        {
            if (LoginSucceeded == null) throw new InvalidOperationException();

            //Invoked and then sent to the App.cs
            LoginSucceeded(sender, EventArgs.Empty);
        }

        public static void LoginCancel(object sender)
        {
            if (LoginCancelled == null) throw new InvalidOperationException();

            //Invoked and then sent to the App.cs
            LoginCancelled(sender, EventArgs.Empty);
        }
    }

The renderer looks like this;

[assembly: ExportRenderer(typeof(OAuthLoginPage), typeof(OAuthLoginPageRenderer))]
namespace MyApp.Droid.Renderers
{    
    public class OAuthLoginPageRenderer : PageRenderer
    {
        public OAuthLoginPageRenderer(Context context) : base(context)
        {

        }

        protected override void OnElementChanged(ElementChangedEventArgs<Page> e)
        {
            base.OnElementChanged(e);

            string idservRootPath = "https://MyApp-idp-o.azurewebsites.net";

            var oAuth = new OAuth2AuthenticatorEx("MyApp.app"
                                    , "openid profile"
                                    , new Uri($"{idservRootPath}/connect/authorize")
                                    , new Uri("com.MyApp.app:/oauth2redirect")
                                    , isUsingNativeUI:false)
            {
                AccessTokenUrl = new Uri($"{idservRootPath}/connect/token"),
                ShouldEncounterOnPageLoading = false
            };

            var account = Task.Run(async () => await App.GetCurrentUserAccountAsync(Serviceconstants.oAuthAccountServiceId)).ConfigureAwait(false)
                                                    .GetAwaiter()
                                                    .GetResult();

            if (account != null)
            {
                App.AuthAccount = account;
                App.HttpClient.AddDefaultRequestHeaderIfNotExists("Authorization", $"Bearer {account.Properties["access_token"]}");

                OAuthLoginPage.LoginSuccess(null);
            }
            else
            {
                oAuth.Completed += Presenter_Completed;
                oAuth.Error += Presenter_Error;

                var presenter = new OAuthLoginPresenter();
                presenter.Completed += Presenter_Completed;
                presenter.Login(oAuth);
            }
        }

        private void Presenter_Error(object sender, AuthenticatorErrorEventArgs e)
        {
            if (!string.IsNullOrWhiteSpace(e.Message))
            {
            }            
        }

        private void Presenter_Completed(object sender, AuthenticatorCompletedEventArgs e)
        {
            if (e.IsAuthenticated)
            {
                App.AuthAccount = e.Account;
                App.HttpClient.AddDefaultRequestHeaderIfNotExists("Authorization", $"Bearer {App.AuthAccount.Properties["access_token"]}");

                Task.Run(async () => await App.SaveAccountAsync(e.Account, Serviceconstants.oAuthAccountServiceId).ConfigureAwait(false));

                OAuthLoginPage.LoginSuccess(sender);
            }       
        }
    }
}

As you can see when the login is a succes, and event is being used to trigger the redirect to the mainpage. This happens in the App itsself;

public App()
        {
            InitializeComponent();

            //Events fired from the LoginPage to trigger actions here
            OAuthLoginPage.LoginSucceeded += HandleLoginSucceeded;
            OAuthLoginPage.LoginCancelled += CancelLoginAction;

            MainPage = new MainPage();
        }

and

private void HandleLoginSucceeded(object sender, EventArgs e)
        {
            //awaits writing token to storage and resets the MainPage UI
            StoreToken();

            _accountHasBeenInvalidated = false;
            MainPage = new MainPage();
        }

        private void CancelLoginAction(object sender, EventArgs e)
        {
            //if login cancelled, user will be redirected back to the sign-in page
            MainPage = new NavigationPage(new SignIn());
        }

I can't get my head around the fact that I keep getting a blank page, does anybody have any idea what this could be?