How to log in to Facebook in Xamarin.Forms

Question

I want to make a Xamarin.Forms project, targeting iOS, Android and Windows Phone.

My app needs to authenticate users using Facebook.

Should I implement login

Answer 1

The correct implementation for the Androids PageRenderer is:

using System;
using Android.App;
using Android.Content;
using OAuth2Demo.XForms.Android;
using Xamarin.Auth;
using Xamarin.Forms;
using Xamarin.Forms.Platform.Android;
using XamarinAuth;

[assembly: ExportRenderer(typeof(LoginPage), typeof(LoginPageRenderer))]

namespace OAuth2Demo.XForms.Android
{
    public class LoginPageRenderer : PageRenderer
    {
        public LoginPageRenderer(Context context) : base(context) { }

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

            // this is a ViewGroup - so should be able to load an AXML file and FindView<>
            var activity = this.Context as Activity;

            var auth = new OAuth2Authenticator(
                clientId: "", // your OAuth2 client id
                scope: "", // the scopes for the particular API you're accessing, delimited by "+" symbols
                authorizeUrl: new Uri(""), // the auth URL for the service
                redirectUrl: new Uri("")); // the redirect URL for the service

            auth.Completed += (sender, eventArgs) =>
            {
                if (eventArgs.IsAuthenticated)
                {
                    App.SuccessfulLoginAction.Invoke();
                    // Use eventArgs.Account to do wonderful things
                    App.SaveToken(eventArgs.Account.Properties["access_token"]);
                }
                else
                {
                    // The user cancelled
                }
            };

            activity.StartActivity(auth.GetUI(activity));
        }
    }
}