Unable to show OAuth Login from Xamarin.Forms modal Page

Xamarin.Auth Issue

Version

• component version = 1.7.0

Steps to reproduce

1. Open a Xamarin.Forms modal page
2. Create an OAuth2Authenticator
3. Create an OAuthLoginPresenter
4. Call OAuthLoginPresenter.Login from the modal page

I’ve attached a MCVE that reproduces the issue:

ModalAuthTest.zip

Platform:

• .NET Standard 2.0
• mono 6.6
• iOS 13.1.2
• Xamarin.iOS 13.8.1.1 (Preview)
• Xcode 11.1
• Visual Studio 16.4 (Preview 2)

(I am using the Visual Studio 16.4 P2 because debugging failed with 16.3, but the issue occurred when using 16.3 with Xamarin.iOS 13.2 and mono 6.0, too)

Expected behaviour

The application should show the OAuth login page to authenticate the user with the app.

Actual behaviour

The web view is not shown and a warning is displayed on the debug output

Warning: Attempt to present <SFSafariViewController: 0x10aa65600> on <Xamarin_Forms_Platform_iOS_PlatformRenderer: 0x10725f950> whose view is not in the window hierarchy!

[AlexSchuetz]

I experienced a similar problem, but with another warning. The problem originated in the Presenter choosing the wrong ViewController. Fortunately I was able to inject my own Presenter:

public class MyPresenter
{
        UIKit.UIViewController rootViewController;

        public void Login(Authenticator authenticator)
        {
            authenticator.Completed += AuthenticatorCompleted;

            rootViewController = GetCurrentUIController();
            rootViewController.PresentViewController(authenticator.GetUI(), true, null);
        }

        void AuthenticatorCompleted(object sender, AuthenticatorCompletedEventArgs e)
        {
            rootViewController?.DismissViewController(true, null);
            ((Authenticator)sender).Completed -= AuthenticatorCompleted;
            // always think of the GC ;)
            rootViewController = null;
        }

        private UIViewController GetCurrentUIController()
        {
            UIViewController viewController;
            var window = UIApplication.SharedApplication.KeyWindow;
            if (window == null)
            {
                throw new InvalidOperationException("There's no current active window");
            }

            viewController = window.RootViewController;

            while (viewController.PresentedViewController != null)
            {
                viewController = viewController.PresentedViewController;
            }

            return viewController;
        }
}

and in AppDelegate I changed:

//global::Xamarin.Auth.Presenters.XamarinIOS.AuthenticationConfiguration.Init();
global::Xamarin.Auth.Presenters.OAuthLoginPresenter.PlatformLogin = (authenticator) =>
{
        var oauthLogin = new MyPresenter();
        oauthLogin.Login(authenticator);
};

Currently I still have a error dialog popping up (cannot open URL), but authentication works. I will post an update as soon as I got rid of the error dialog.

UPDATE The “Cannot open URL”-error dialog was due to a configuration error (wrong URL scheme in info.plist).

[andygikling]

Yes @AlexSchuetz thank you for the insight. I might have to step back and rethink this a bit here.