single sign on - Facebook authorization fails on iOS6 when switching FB account on device

Question

I'm using die Facebook SDK 3.1.1 to implement FB Connect in my iOS application. This works fine in the simple case with either the new FB integration (logged in on iOS) or falling back to the normal authorization via web view (I do not have the native Facebook application installed in both cases). The problem occurs when I switch the account on iOS level. Logging out and logging in with a different FB user account.

To log in/authorize I perform:

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

If then get a FBSessionStateClosedLoginFailed every time even though I perform a closeAndClearTokenInformation when that state is reached:

- (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;
}

However, I receive the same state on every retry. My log says the following:

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}

Can anyone reproduce this or has any idea where the problem might lie?

Answer 1

Another answer gives a way to manually resync the device with the server. I defined a method called fbRsync to call this code. Make sure to #import <Accounts/Accounts.h> in your implementation file and then define this method:

-(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){

        }
    }];
}

}

I then call fbResync if openActiveSessionWithReadPermissions yields an error:

[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];
 }];

The half a second delay is likely unnecessary, but it currently gives me piece of mind.

This seems to solve the problem for me. I can now switch between Facebook accounts and am able to log in. Yay!