C#-使用Xamarin.Android为Parse.com服务器制作更漂亮的Facebook登录屏幕

我正在尝试为Xamarin.Android创建一个登录系统以在解析服务器上使用.我想用Facebook登录该用户,并保存他的真实姓名和小用户照片.
我当前显示登录系统的代码是这样的：

using Xamarin.Auth;

loginFacebookButton.Click += (sender, e) =>
        {

            if (CrossConnectivity.Current.IsConnected)
                LoginToFacebook();
            else
            {
                DisplayNoConnectivityMessage();
            }

        };

        loginTwitterButton.Click += (sender, e) =>
        {
            LoginToTwitter();
        };
    }

    void DisplayNoConnectivityMessage()
    {
        AlertDialog.Builder alert2 = new AlertDialog.Builder(this);
        alert2.SetTitle("Network error");
        alert2.SetMessage("Connection with the Internet is required. Please check your connectivity and try again.");
        alert2.Show();

    }

    void DisplayLoadingMessage(bool Dismiss)
    {
        RunOnUiThread(() =>
        {
            if (!Dismiss)
            {
                builder = new AlertDialog.Builder(this);

                builder.SetTitle("Signing in");
                builder.SetMessage("Please wait...");
                builder.SetCancelable(false);
                alert = builder.Create();
                alert.Show();

            } else {
                if (alert != null)
                    if (alert.IsShowing)
                    { 
                        alert.Dismiss();
                        alert.Dispose();
                    }
            }
        });

    }

    async void LoginToFacebook()
    {
        var auth = new OAuth2Authenticator(
            clientId: "809804315805408",
            scope: "user_about_me",
            authorizeUrl: new Uri("https://m.facebook.com/dialog/oauth/"),
            redirectUrl: new Uri("http://www.facebook.com/connect/login_success.html")
        );

        auth.AllowCancel = false;

        // If authorization succeeds or is canceled, .Completed will be fired.
        auth.Completed += LoginComplete;

        var intent = auth.GetUI(this);
        StartActivity(intent);
    }

    public async void LoginComplete(object sender, AuthenticatorCompletedEventArgs e)
    {
        string id = "";
        string name = "";
        JsonValue obj;
        if (!e.IsAuthenticated)
        {
            var builder = new AlertDialog.Builder(this);
            builder.SetMessage("Not Authenticated");
            builder.SetPositiveButton("Ok", (o, c) => { });
            builder.Create().Show();
            return;
        }
        else {

            DisplayLoadingMessage(false);
            AccountStore.Create(this) .Save(e.Account, "Facebook");
            // Now that we're logged in, make a OAuth2 request to get the user's info.
            var request = new OAuth2Request("GET", new Uri("https://graph.facebook.com/me"), null, e.Account);
            await request.GetResponseAsync().ContinueWith(t =>
            {
                var builder2 = new AlertDialog.Builder(this);
                if (t.IsFaulted)
                {
                    builder2.SetTitle("Error");
                    builder2.SetMessage(t.Exception.Flatten().InnerException.ToString());
                    builder2.Show();
                }
                else if (t.IsCanceled)
                {
                    builder2.SetTitle("Task Canceled");
                    builder2.Show();
                }
                else {
                    obj = JsonValue.Parse(t.Result.GetResponseText());
                    id = obj["id"];
                    name = obj["name"];
                }

                builder.SetPositiveButton("Ok", (o, c) => { });
                builder.Create();
            }, UIScheduler);

            var accessToken = e.Account.Properties["access_token"];
            var expiresIn = Convert.ToDouble(e.Account.Properties["expires_in"]);
            var expiryDate = DateTime.Now + TimeSpan.FromSeconds(expiresIn);
            var user = await ParseFacebookUtils.LogInAsync(id, accessToken, expiryDate);

            try
            {
                user.Add("Name", name);
            }
            catch (Exception ex)
            {
                Console.WriteLine("LoginFragment.cs | LoginComplete() :: user.Add (\"Name\",name); :: " + ex.Message);
            }

            var webClient = new WebClient();
            //var httpClient = new HttpClient(new NativeMessageHandler());
            var url = new Uri("http://graph.facebook.com/" + id + "/picture?type=small");
            application.currentUserImageUrl = url.ToString();
            application.currentUserName = name;
            byte[] bytes = null;
            //bytes = await httpClient.GetByteArrayAsync(url);
            bytes = await webClient.DownloadDataTaskAsync(url);

            ParseFile saveImageFile = new ParseFile("profileImage.jpg", bytes);
            try
            {
                user.Add("profile_pic", saveImageFile);
            }
            catch (Exception ex)
            {
                Console.WriteLine("LoginFragment.cs | LoginComplete() :: user.Add (\"profile_pic\",saveImageFile); :: " + ex.Message);
            }

            application.currentUser = user;
            await user.SaveAsync();
            DisplayLoadingMessage(true);
            ChangeScreen();
        }
    }

此代码的问题是这样的：

>登录后,我会显示一条成功消息(简单
白页上的成功消息)必须来自Facebook和
显然,我不愿意在用户身上显示.
>虽然
LoginCompete代码正在运行,应用程序正在后台运行,并且用户看不到任何提示,就像应用程序关闭后
登录再次打开.我试图显示一个AlertDialog与
函数DisplayNoConnectivityMessage但未显示
在用户什么我不知道的方式.

解决方法:

在Parse上用Facebook登录的最简单方法是将官方的Parse SDK与官方的Android SDK版Facebook结合使用以处理单一登录方案.

仅需一些小步骤,即可达到预期的结果：

>按照此小型指南为Facebook SDK设置应用：https://components.xamarin.com/gettingstarted/facebookandroid
>设置解析SDK

public App()
{
    // App.xaml initialization
    ParseClient.Initialize("Your Application ID", "Your .NET Key");
    ParseFacebookUtils.Initialize("Your Facebook App Id");
    // Other initialization
}

>将FB登录按钮添加到视图中.

<com.facebook.login.widget.LoginButton
  android:id="@+id/login_button"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:layout_gravity="center_horizontal"
  android:layout_marginTop="30dp"
  android:layout_marginBottom="30dp" />   

>获取回调,并使用令牌通过Parse登录用户.

public class MainActivity : Activity, IFacebookCallback
{
    protected override void OnCreate(Bundle bundle)
    {
        base.OnCreate(bundle);

        // Set our view from the "main" layout resource
        // SetContentView (Resource.Layout.Main);

        var callbackManager = CallbackManagerFactory.Create();

        var loginButton = FindViewById<LoginButton>(Resource.Id.login_button);
        loginButton.RegisterCallback(callbackManager, this);
    }

    #region IFacebookCallback

    public void OnCancel()
    {
        // Handle Cancel
    }

    public void one rror(FacebookException error)
    {
        // Handle Error
    }

    public async void OnSuccess(Object result)
    {
        // We know that this is a LoginResult
        var loginResult = (LoginResult) result;

        // Convert Java.Util.Date to DateTime
        var epoch = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);
        var expireDate = epoch.AddMilliseconds(loginResult.AccessToken.Expires.Time);

        // FB User AccessToken
        var accessToken = loginResult.AccessToken.Token;

        ParseUser user = await ParseFacebookUtils.LogInAsync("Your Facebook App Id", accessToken, expireDate);
    }

    #endregion
... 
}

>(可选)与Facebook SDK& ParseUser

// You can simply pass the acquired AccessToken to the GraphRequest
var parameters = new Bundle();
parameters.PutString("fields", "id,email,gender,cover,picture.type(small)");
var request = new GraphRequest(loginResult.AccessToken, "me", parameters, HttpMethod.Get);

// Execute request and Handle response (See FB Android SDK Guide)
// to get image as byte[] from GraphResponse
byte[] data;

// Store the image into the ParseUser
user["image"] = new ParseFile("image.jpg", data);

Instead of using the GraphRequest you can always fallback to the HttpClient / WebClient and pass the AccessToken as URL parameter. 07002

额外

这里是官方文档的链接：http://parseplatform.github.io/docs/dotnet/guide/#facebook-users

从Nuget选择SDK：https://www.nuget.org/packages/Xamarin.Facebook.Android/

Xamarin Facebook Android SDK的工作方式类似于Java SDK,因此,该文档也值得一看：https://developers.facebook.com/docs/facebook-login/android#addbutton

标签：parse-platform,xamarin,facebook-login,c,android
来源： https://codeday.me/bug/20191026/1937222.html