我使用以下代码进行Facebook登录并访问用户信息，如专辑和图片。我已使用以下代码设置代码以获取访问令牌。现在，问题是每次用户打开应用程序时我都需要获取访问令牌。但是，一旦用户进行身份验证，应用程序将不会要求验证，直到用户关闭应用程序。但是在用户重新打开应用程序后，它会再次要求进行身份验证。这样，如果用户每次尝试访问专辑或Facebook的任何其他内容时都会要求身份验证，用户就会感到沮丧。
有没有想跳过这个？我的意思是一旦用户提供访问Facebook，应用程序不得要求登录（身份验证）。我将拥有访问令牌，但我不知道如何使用身份验证。因此，我们可以经常避免身份验证。
我的代码：
public class FacebookService : IFacebookService
{
private readonly string[] permissions = { "public_profile", "email", "user_birthday", "user_photos" };
public event EventHandler<FacebookUser> LoginCompleted;
public string Token => AccessToken.CurrentAccessToken.TokenString;
public void Logout()
{
LoginManager manager = new LoginManager();
manager.LogOut();
}
public void LogInToFacebook()
{
if (AccessToken.CurrentAccessToken == null)
{
ObtainNewToken(LogInToFacebook);
return;
}
var fields = new[] { "name", "email", "birthday", "gender", "picture" };
var query = $"/me?fields={string.Join(",", fields)}";
var token = AccessToken.CurrentAccessToken.TokenString;
var request = new GraphRequest(query, null, token, null, "GET");
request.Start((connection, result, error) =>
{
if (error != null)
{
HandleError(error.LocalizedDescription);
}
else
{
var userInfo = result as NSDictionary;
var id = userInfo["id"].ToString();
var email = userInfo["email"].ToString();
var name = userInfo["name"].ToString();
var birthday = userInfo["birthday"].ToString();
var gender = userInfo["gender"].ToString();
var picture = ((userInfo["picture"] as NSDictionary)["data"] as NSDictionary)["url"].ToString();
var args = new FacebookUser(id, email, name, birthday, gender, picture);
LoginCompleted?.Invoke(this, args);
}
});
}
public async System.Threading.Tasks.Task RequestAlbums(Action<FacebookAlbum[]> callback)
{
if (AccessToken.CurrentAccessToken == null)
{
ObtainNewTokenForAlbum(callback);
return;
}
using (HttpClient client = new HttpClient())
{
try
{
client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", Token);
var host = "https://graph.facebook.com/";
var json = await client.GetStringAsync($"{host}me/albums");
var data = JObject.Parse(json).First.First.ToString();
var albums = JsonConvert.DeserializeObject<FacebookAlbum[]>(data);
var getPhotosTasks = new List<System.Threading.Tasks.Task>();
foreach (var album in albums)
getPhotosTasks.Add(System.Threading.Tasks.Task.Run(() => RequestPhotos(album)));
await System.Threading.Tasks.Task.WhenAll(getPhotosTasks.ToArray());
callback(albums);
}
catch (Exception ex1)
{
HandleError(ex1.Message);
}
}
}
private void ObtainNewTokenForAlbum(Action<FacebookAlbum[]> callback)
{
var login = new LoginManager();
login.LogInWithReadPermissions(permissions, null, (r, e) =>
{
if (e == null && !r.IsCancelled)
{
RequestAlbums(callback);
}
else
HandleError(e?.LocalizedDescription);
});
}
private async System.Threading.Tasks.Task RequestPhotos(FacebookAlbum album)
{
using (HttpClient client = new HttpClient())
{
client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", Token);
try
{
var host = "https://graph.facebook.com/";
var json = await client.GetStringAsync($"{host}{album.Id}/photos?fields=source,picture");
var data = JObject.Parse(json)["data"].ToString();
album.Photos = JsonConvert.DeserializeObject<FacebookPicture[]>(data);
}
catch (Exception exc)
{
HandleError(exc.Message);
}
}
}
private void ObtainNewToken(Action callback)
{
var login = new LoginManager();
login.LogInWithReadPermissions(permissions, null, (r, e) =>
{
if (e == null && !r.IsCancelled)
callback?.Invoke();
else
HandleError(e?.LocalizedDescription);
});
}
private void HandleError(string messageDescription)
{
messageDescription = messageDescription ?? "Request was cancelled";
_notificationService.DisplayNotification(messageDescription, Colors.d8Red);
}
}
的AppDelegate
public override bool FinishedLaunching(UIApplication uiApplication, NSDictionary launchOptions)
{
UAirship.TakeOff();
RegisterServices();
SetupFacebookSDK();
FFImageLoading.Forms.Touch.CachedImageRenderer.Init();
var dummy = new FFImageLoading.Forms.Touch.CachedImageRenderer();
Xamarin.Forms.Forms.Init();
LoadApplication(new App());
UIApplication.SharedApplication.StatusBarHidden = false;
UIApplication.SharedApplication.SetStatusBarStyle(UIStatusBarStyle.LightContent, false);
_networkManager = new NetworkManager();
OverrideDefaultListViewCustomActionsColors();
UAirship.Push.UserPushNotificationsEnabled = true;
new PhotoAccessChecker();
return ApplicationDelegate.SharedInstance.FinishedLaunching(uiApplication, launchOptions);
}
void SetupFacebookSDK()
{
FacebookProfile.EnableUpdatesOnAccessTokenChange(true);
FacebookSettings.AppID = "000000000049000";
FacebookSettings.DisplayName = "MyProduct";
}
public override bool OpenUrl(UIApplication application, NSUrl url, string sourceApplication, NSObject annotation)
{
return ApplicationDelegate.SharedInstance.OpenUrl(application, url, sourceApplication, annotation);
}
答案 0 :(得分：1)
我猜你忘了在AppDelegate中初始化FBSDK。
如果return ApplicationDelegate.SharedInstance.FinishedLaunching (application, launchOptions);已执行FinishedLaunching，请检查您的代码。
public override bool FinishedLaunching (UIApplication app, NSDictionary options)
{
Settings.AppID = appId;
Settings.DisplayName = appName;
// ...
// This method verifies if you have been logged into the app before, and keep you logged in after you reopen or kill your app.
return ApplicationDelegate.SharedInstance.FinishedLaunching (application, launchOptions);
}
public override bool OpenUrl (UIApplication application, NSUrl url, string sourceApplication, NSObject annotation)
{
// We need to handle URLs by passing them to their own OpenUrl in order to make the SSO authentication works.
return ApplicationDelegate.SharedInstance.OpenUrl (application, url, sourceApplication, annotation);
}