使用Game Center验证本地玩家

我正在尝试验证游戏中心的玩家身份。然而,苹果提供的代码

- (void) authenticateLocalPlayer
{
    [[GKLocalPlayer localPlayer] authenticateWithCompletionHandler:^(NSError *error) {
         if (error == nil)
         {
              // Insert code here to handle a successful authentication.
              NSLog(@"Logged in.");
         }
         else
         {
             // Your application can process the error parameter to report the error to the player.
             NSLog(@"%@", [error description]);
         }
     }];
}

如果按retry,将出现以下错误:

Error Domain=GKErrorDomain Code=7 "The requested operation could not be completed because local player is already authenticating." UserInfo=0x8915f80 {NSLocalizedDescription=The requested operation could not be completed because local player is already authenticating.}