ITブログ時々なんでもブログ

using System.Threading.Tasks;
using Xamarin.Forms;
namespace AppName.Views
{
    public partial class FacebookTestPage : ContentPage
    {
        public FacebookTestPage() 
        {
            InitializeComponent();
        }

        private const string AppId = "999999999999999";
        private const string FacebookLoginUrl = "http://www.facebook.com/connect/login_success.html";

        /// <summary>
        /// Facebookログイン画面を表示する
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        async void OnLoginClick(object sender, EventArgs e)
        {
            try
            {  
                //パーミッションの結合文字列（カンマをURLエンコード）
                const string and = "%2C";

                //ログインURL（アクセストークン要求）
                var apiRequest =
                    "http://www.facebook.com/v2.9/dialog/oauth" +
                    "?client_id=" + AppId +
                    "&display=popup" +
                    "&response_type=token" + 
                    "&redirect_uri=" + System.Net.WebUtility.UrlEncode(FacebookLoginUrl) +
                    //パーミッション
                    "&scope=email" + and +          //デフォルトで使用が許可されている
                            "user_friends" + and +  //デフォルトで使用が許可されている
                            "user_birthday"         //使用にはFacebookに申請が必要
                            ;

                var webView = new WebView
                {
                    Source = apiRequest,
                    HeightRequest = 1
                };

                webView.Navigated += OnWebViewNavigated;
                Content = webView;
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message + System.Environment.NewLine + ex.StackTrace);
            }
        }

        /// <summary>
        /// WebViewの遷移イベント
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private async void OnWebViewNavigated(object sender, WebNavigatedEventArgs e)
        {
            var accessToken = ExtractAccessTokenFromUrl(e.Url);
            if (!String.IsNullOrEmpty(accessToken))
            {
                await GetFacebookProfileAsync(accessToken);
            }
        }

        /// <summary>
        /// Url文字列からアクセストークンを取得する
        /// </summary>
        /// <param name="url">URL文字列</param>
        /// <returns></returns>
        private string ExtractAccessTokenFromUrl(string url)
        {
            if (url.Contains("access_token") && url.Contains("&expires_in="))
            {
                var at = url.Replace(FacebookLoginUrl + "#access_token=", "");

                var token = at.Remove(at.IndexOf("&expires_in="));
                return token;
            }

            return String.Empty;
        }

        /// <summary>
        /// Facebookプロフィール情報を取得する
        /// </summary>
        /// <param name="accessToken">アクセストークン</param>
        /// <returns></returns>
        private async Task GetFacebookProfileAsync(string accessToken)
        {
            var requestUrl =
                "https://graph.facebook.com/me?" +
                "fields=id,name,first_name,last_name,email,gender,birthday,age_range,picture,cover,devices,is_verified&" +
                "access_token=" + accessToken;
            var httpClient = new System.Net.Http.HttpClient();
            var json = await httpClient.GetStringAsync(requestUrl);
            var profile = Newtonsoft.Json.JsonConvert.DeserializeObject<FacebookProfile>(json);

            //情報を取得する
            string id = profile.Id;
            string firstName = profile.First_Name;
            string lastName = profile.Last_Name;
            string email = profile.Email;
            string gender = profile.Gender;
        }
    }
}