iphone - 从 iOS 发布到 Facebook 时间线的第一次尝试会出现 HTTP 400

Question

我正在遵循 facebook SDK 上提供的教程:

Login with facebook using the ios SDK

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一切似乎都工作正常，除了测试我的应用程序之外，我在第一次尝试发布到 Facebook 墙时收到 HTTP 错误 400(或错误代码 5)。如果我在应用程序中再次按下“发布”按钮，第二次，一切似乎都正常。第一次尝试时，用户被发送到 facebook 应用程序进行身份验证，然后切换回应用程序，然后给我 HTTP 400。第二次尝试时，没有应用程序切换，并且消息按预期发布到 facebook 墙.

我试图弄清楚为什么我的应用程序在第一次尝试时不会发布到墙上/时间线。我的代码与教程中的代码相同。

编辑:

忘了提及，我使用一个按钮来进行身份验证并发布到墙上 - 这是 IBAction 中的代码:

AppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];
    // The user has initiated a login, so call the openSession method
    // and show the login UX if necessary.
    [appDelegate openSessionWithAllowLoginUI:YES];


    [FBRequestConnection startWithGraphPath:@"me/feed" parameters:postParams HTTPMethod:@"POST" completionHandler:^(FBRequestConnection *connection,id result,NSError *error)
    {

        NSString *alertText;

        if (error) {
             alertText = [NSString stringWithFormat:
                          @"error: domain = %@, code = %d", error.domain, error.code];
         } else {
             /*alertText = [NSString stringWithFormat:
                          @"Posted action, id: %@", [result objectForKey:@"id"]];*/
             alertText = @"Posted!";
         }
         // Show the result in an alert
        [[[UIAlertView alloc] initWithTitle:@"Facebook" message:alertText delegate:self cancelButtonTitle:@"OK!" otherButtonTitles:nil] show];
    }];

Answer 1

我通过 mkral 的有用注释解决了这个问题 - 代码更改如下:

AppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];

    if (FBSession.activeSession.isOpen) { //session is open so can post right away

        [FBRequestConnection startWithGraphPath:@"me/feed" parameters:postParams HTTPMethod:@"POST" completionHandler:^(FBRequestConnection *connection,id result,NSError *error)
         {

             NSString *alertText;

             if (error) {
                 alertText = [NSString stringWithFormat:
                              @"error: domain = %@, code = %d", error.domain, error.code];
             } else {
                 alertText = @"Posted!";
             }
             // Show the result in an alert
             [[[UIAlertView alloc] initWithTitle:@"Facebook" message:alertText delegate:self cancelButtonTitle:@"OK!" otherButtonTitles:nil] show];
         }];

    }
    else //session isn't open so authenticate first, then can post when back to app through notification
    {
        NSLog(@"Facebook Active Session not open");
        // The user has initiated a login, so call the openSession method
        // and show the login UX if necessary.
        [appDelegate openSessionWithAllowLoginUI:YES];
    }

因此，我首先检查是否有事件 session - 如果有，我可以将其发布到墙/时间线，如果没有，我会打开一个 session 。然后，我注册了一个通知(在 viewDidLoad 中)，让我知道是否有 session 更改(在本例中，如果 session 打开，就会发生更改)，并且一旦经过身份验证，它就会发布到墙上。

- (void)viewDidLoad
{
    [super viewDidLoad];        

//register for the session change notification you defined in the app delegate (for example when session changes to logged in)
    [[NSNotificationCenter defaultCenter]
     addObserver:self
     selector:@selector(sessionStateChanged:)
     name:FBSessionStateChangedNotification
     object:nil];

}

- (void)sessionStateChanged:(NSNotification*)notification {
    if (FBSession.activeSession.isOpen) {

        [FBRequestConnection startWithGraphPath:@"me/feed" parameters:postParams HTTPMethod:@"POST" completionHandler:^(FBRequestConnection *connection,id result,NSError *error)
         {

             NSString *alertText;

             if (error) {
                 alertText = [NSString stringWithFormat:
                              @"error: domain = %@, code = %d", error.domain, error.code];
             } else {
                 alertText = @"Posted!";
             }
             // Show the result in an alert
             [[[UIAlertView alloc] initWithTitle:@"Facebook" message:alertText delegate:self cancelButtonTitle:@"OK!" otherButtonTitles:nil] show];
         }];

    }
}