facebook - 尝试使用 Facebook JS SDK 从 Facebook 注销时，getLoginStatus 返回未知状态

Question

我有一个本地主机网站，我在其中使用 Facebook C# SDK 通过 Facebook 实现了登录。

启动配置类:

    public class ExternalLoginConfig
    {
        public void ConfigureAuth(IAppBuilder app)
        {
            app.UseExternalSignInCookie(DefaultAuthenticationTypes.ExternalCookie);

            var facebookAuthenticationOptions = new FacebookAuthenticationOptions()
            {
                AppId = ConfigSettings.FacebookAppId,
                AppSecret = ConfigSettings.FacebookAppSecret,
                Scope = { "email" },
                Provider = new FacebookAuthenticationProvider()
                {
                    OnAuthenticated = context =>
                    {
                        var accessToken = context.AccessToken;
                        var facebookClient = new FacebookClient(accessToken);

                        var result = facebookClient.Get("me", new { fields = "email,first_name,last_name" }) as JsonObject;

                        string email = null;
                        string firstName = null;
                        string lastName = null;

                        if (result != null)
                        {
                            email = result.ContainsKey("email") ? (string) result["email"] : null;
                            firstName = result.ContainsKey("first_name") ? (string) result["first_name"] : null;
                            lastName = result.ContainsKey("last_name") ? (string) result["last_name"] : null;
                        }

                        if (firstName != null)
                        {
                            context.Identity.AddClaim(new Claim(ClaimTypes.GivenName, firstName));
                        }
                        if (lastName != null)
                        {
                            context.Identity.AddClaim(new Claim(ClaimTypes.Surname, lastName));
                        }
                        if (email != null)
                        {
                            context.Identity.AddClaim(new Claim(ClaimTypes.Email, email));
                        }

                        return Task.FromResult(0);
                    },
                    OnApplyRedirect = context =>
                    {
                        context.Response.Redirect(context.RedirectUri + "&auth_type=reauthenticate");
                    }
                }
            };
            app.UseFacebookAuthentication(facebookAuthenticationOptions);
        }
    }

Actions form Authentication controller:

    [HttpPost]
    [AllowAnonymous]
    public virtual ActionResult Login(string provider, string returnUrl)
    {
        ControllerContext.HttpContext.Session.RemoveAll();

        return new ExternalLoginResult(provider,
            Url.Action("LoginCallback", "Oauth", new { ReturnUrl = returnUrl }));
    }

    [AllowAnonymous]
    public async Task<ActionResult> LoginCallback(string returnUrl, string error)
    {
        var loginInfo = await AuthenticationManager.GetExternalLoginInfoAsync();

        if (loginInfo == null)
        {
            return Redirect(returnUrl);
        }

        User user = null;
        string userName = Guid.NewGuid().ToString();
        string firstName = loginInfo.ExternalIdentity.FindFirstValue(ClaimTypes.GivenName);
        string lastName = loginInfo.ExternalIdentity.FindFirstValue(ClaimTypes.Surname);
        string email = loginInfo.ExternalIdentity.FindFirstValue(ClaimTypes.Email);
        string externalProviderName = loginInfo.Login.LoginProvider;
        string externalProviderKey = loginInfo.Login.ProviderKey;

        var externalAuthenticationInfo = new ExternalAuthenticationInfo()
        {
            Username = userName,
            Email = email,
            FirstName = firstName,
            LastName = lastName,
            ExternalProviderName = externalProviderName,
            ExternalProviderKey = externalProviderKey
        };

        var loginResult = userProvider.ExternalLogin(externalProviderKey, email, out user);

        switch (loginResult)
        {
            case LoginResult.Success:
            {
                AuthenticationHelper.SetAuthenticatedUserId(user.ID);
                break;
            }
            case LoginResult.NotRegistered:
            {
                var registerResult = userProvider.Register(userName, email, null, externalAuthenticationInfo);

                if (registerResult.IsValid)
                {
                    AuthenticationHelper.SetAuthenticatedUserId(registerResult.Result.ID);
                }

                break;
            }
        }

        return Redirect(returnUrl);
    }

Facebook JS SDK 初始化:

    window.fbAsyncInit = function () {
        FB.init({
            appId: '@ConfigSettings.FacebookAppId',
            xfbml: true,
            version: 'v2.4'
        });
    };

    (function (d, s, id) {
        var js, fjs = d.getElementsByTagName(s)[0];
        if (d.getElementById(id)) { return; }
        js = d.createElement(s); js.id = id;
        js.src = "//connect.facebook.net/en_US/sdk.js";
        fjs.parentNode.insertBefore(js, fjs);
    }(document, 'script', 'facebook-jssdk'));

我正在尝试使用 Facebook JS SDK 将用户从 facebook 中注销，但是调用:

    FB.getLoginStatus(function facebookLogoutCallback(facebookResponse) {
        if (facebookResponse.status !== 'connected') {
            return;
        }

        FB.logout(facebookLogoutCallback);
    });

导致状态 unknown 而不是 connected，它在 facebookResponse 对象中返回。我也试过在没有 if 语句的情况下调用 FB.logout()，但没有成功。

也许你可以说，这种行为是由未经授权的用户状态引起的，但在服务器端登录后，用户实际上已经登录了:在我的网站和 Facebook 上也是如此。

Answer 1

目前 FB.logout 函数中似乎存在错误。调用它后，用户无法使用 JS SDK 再次登录此应用程序，因为 FB.login 函数返回
对象 { status="unknown", authResponse=null}

编辑:
发现在 FB.logout() 之后创建了一个名为“fblo_*”的 cookie，这似乎是造成这种情况的原因。我不能确切地说出它存在的原因以及它的作用，但删除它会使登录重新生效。

因此我创建了一个小脚本来查找这个 cookie 并在我调用 FB.login() 之前删除它，您可能想在点击事件 ( https://developers.facebook.com/docs/reference/javascript/FB.login/v2.5 ) 中调用它。

function delete_cookie(name) 
{
    document.cookie = name + '=; expires=Thu, 01 Jan 1970 00:00:01 GMT; path=/';
}


var cookies = document.cookie.split(";");
for (var i = 0; i < cookies.length; i++)
{
    if(cookies[i].split("=")[0].indexOf("fblo_") != -1)
        delete_cookie(cookies[i].split("=")[0]);
}