Xamarin auth view close issue

Question

I'm implementing facebook login to Xamarin forms proejct using Xamarin.Auth plugin. This is ios render code.

When I click cancel button or login successfully, dismissviewcontroller is called and the web view is closed.

When I click this facebook or login button again, I'm getting below error.

Warning: Attempt to present on whose view is not in the window hierarchy!

If anyone has a good solution, please help me.

[assembly: ExportRenderer(typeof(FBLoginPage), typeof(FBLoginPageRenderer))]
namespace vidmoji.iOS
{
    public class FBLoginPageRenderer : PageRenderer
    {
        bool IsShown;


        public override void ViewDidAppear(bool animated)
        {
            base.ViewDidAppear(animated);

            if (!IsShown)
            {
                IsShown = true;

                var auth = new OAuth2Authenticator(
                    clientId: App.Instance.FBAuthSettings.ClientId,
                    clientSecret: App.Instance.FBAuthSettings.SecurityKey,
                    accessTokenUrl: new Uri(App.Instance.FBAuthSettings.AccessTokenUrl),
                    scope: App.Instance.FBAuthSettings.Scope,
                    authorizeUrl: new Uri(App.Instance.FBAuthSettings.AuthorizeUrl),
                    redirectUrl: new Uri(App.Instance.FBAuthSettings.RedirectUrl));



                auth.Completed += (sender, eventArgs) =>
                {
                    DismissViewController(true, null);
                    if (eventArgs.IsAuthenticated)
                    {
                        App.Instance.loginWithFacebook(eventArgs.Account.Properties["access_token"]);
                    }
                    else {
                        DismissModalViewController(true);
                    }
                };

                PresentViewController(auth.GetUI(), true, null);
            }
        }
    }
}

Answer 1

Updating the answer

In your FBLoginPage add a public method.

public partial class FBLoginPage : ContentPage
{
    //......

    public void OnAuthenticationCompleted (bool isAuthenticated, string accessToken)
    {
        //Get your token and do what you need to do with it.
        Navigation.PopModalAsync (true);
    }
}

and your renderer class change it to:

public override void ViewDidAppear (bool animated)
{
    base.ViewDidAppear (animated);

    if (!IsShown)
    {
        IsShown = true;

        var auth = new OAuth2Authenticator(
            clientId: App.Instance.FBAuthSettings.ClientId,
            clientSecret: App.Instance.FBAuthSettings.SecurityKey,
            accessTokenUrl: new Uri(App.Instance.FBAuthSettings.AccessTokenUrl),
            scope: App.Instance.FBAuthSettings.Scope,
            authorizeUrl: new Uri(App.Instance.FBAuthSettings.AuthorizeUrl),
            redirectUrl: new Uri(App.Instance.FBAuthSettings.RedirectUrl));

        auth.Completed += (sender, eventArgs) => {

            var element = Element as LoginPage;

            var token = eventArgs.IsAuthenticated ? eventArgs.Account.Properties ["access_token"] : null;

            element?.OnAuthenticationCompleted (eventArgs.IsAuthenticated, token);
        };

        PresentViewController (auth.GetUI (), true, null);
    }

}

Regarding the update.

This component is not updated since 2 years ago but the nuget package is. I suggestion to change from the the component to the Nuget package.

Good luck.