在 iOS6 上切换设备上的 FB 帐户时 Facebook 授权失败

我正在使用 Facebook SDK 3.1.1 在我的 iOS 应用程序中实现 FB Connect。在简单的情况下，无论是使用新的 FB 集成（在 iOS 上登录）还是通过 Web 视图返回到正常授权（在这两种情况下我都没有安装本机 Facebook 应用程序），这都可以正常工作。 当我在 iOS 级别切换帐户时会出现此问题。使用不同的 FB 用户帐户注销和登录。

要登录/授权，我执行：

[FBSession openActiveSessionWithReadPermissions:nil allowLoginUI:allowLoginUI
                                     completionHandler:^(FBSession *session, FBSessionState state, NSError *error) {
                                         [self sessionStateChanged:session state:state error:error];
                                     }];

如果然后每次都会得到 FBSessionStateClosedLoginFailed 即使我执行closeAndClearTokenInformation当达到该状态时：

- (void)sessionStateChanged:(FBSession *)session
                  state:(FBSessionState) state
                  error:(NSError *)error
{
    NSLog(@"Session State Changed: %u", [[FBSession activeSession] state]);
    switch (state) {
        case FBSessionStateOpen:
            break;
        case FBSessionStateClosed:
        case FBSessionStateClosedLoginFailed:
            NSLog(@"FBSessionStateClosedLoginFailed ERROR: %@", [error description]);
            [[FBSession activeSession] closeAndClearTokenInformation];
            break;
        default:
            break;
}

但是，每次重试时我都会收到相同的状态。我的日志内容如下：

FBSDKLog: FBSession **INVALID** transition from FBSessionStateCreated to FBSessionStateClosed
FBSDKLog: FBSession transition from FBSessionStateCreated to FBSessionStateCreatedOpening 
FBSDKLog: FBSession transition from FBSessionStateCreatedOpening to FBSessionStateClosedLoginFailed Session State Changed: 257
FBSessionStateClosedLoginFailed TOKEN: (null)
FBSessionStateClosedLoginFailed ERROR: Error Domain=com.facebook.sdk Code=2 "The operation couldn’t be completed. (com.facebook.sdk error 2.)" UserInfo=0xb24cc20 {com.facebook.sdk:ErrorLoginFailedReason=com.facebook.sdk:ErrorLoginFailedReason}

任何人都可以重现这个或知道问题可能出在哪里吗？

另一个答案 https://stackoverflow.com/questions/12601191/facebook-sdk-3-1-error-validating-access-token提供了一种手动将设备与服务器重新同步的方法。我定义了一个名为fbRsync来调用这段代码。确保#import <Accounts/Accounts.h>在您的实现文件中，然后定义此方法：

-(void)fbResync
{
    ACAccountStore *accountStore;
    ACAccountType *accountTypeFB;
    if ((accountStore = [[ACAccountStore alloc] init]) && (accountTypeFB = [accountStore accountTypeWithAccountTypeIdentifier:ACAccountTypeIdentifierFacebook] ) ){

    NSArray *fbAccounts = [accountStore accountsWithAccountType:accountTypeFB];
    id account;
    if (fbAccounts && [fbAccounts count] > 0 && (account = [fbAccounts objectAtIndex:0])){

    [accountStore renewCredentialsForAccount:account completion:^(ACAccountCredentialRenewResult renewResult, NSError *error) {
        //we don't actually need to inspect renewResult or error.
        if (error){

        }
    }];
}

}

然后我打电话fbResync if openActiveSessionWithReadPermissions产生错误：

[FBSession openActiveSessionWithReadPermissions:permissions
                                   allowLoginUI:YES
                              completionHandler:^(FBSession *session, FBSessionState state, NSError *error) {
     if(error)
     {
         NSLog(@"Session error");
         [self fbResync];
         [NSThread sleepForTimeInterval:0.5];   //half a second
         [FBSession openActiveSessionWithReadPermissions:permissions
                                            allowLoginUI:YES
                                       completionHandler:^(FBSession *session, FBSessionState state, NSError *error) {
            [self sessionStateChanged:session state:state error:error];
                                       }];

     }
     else
         [self sessionStateChanged:session state:state error:error];
 }];

半秒的延迟可能是不必要的，但它目前让我放心了。

这似乎为我解决了问题。我现在可以在 Facebook 帐户之间切换并能够登录。耶！