Youtube视频缩略图未显示

Question

我正在使用iOS SDK 3.2.1发布用户墙。一切都很好，但如果我发布Youtube视频，它的缩略图不会显示。 我的发布代码是这样的：

postParams =[[NSMutableDictionary alloc] init];
[postParams setObject:link forKey:@"link"];
[postParams setObject:name forKey:@"name"];
[postParams setObject:desc forKey:@"description"];
[postParams setObject:url forKey:@"source"];
[postParams setObject:message forKey:@"message"];



AppDelegate *appdel=[[UIApplication sharedApplication] delegate];
appdel.session=[[FBSession alloc] init];
[appdel.session openWithCompletionHandler:^(FBSession *session,
                                                    FBSessionState status,
                                                    NSError *error)
         {
         }];
        [FBSession setActiveSession:appdel.session];
        [FBRequestConnection startWithGraphPath:@"me/feed" parameters:postParams                 HTTPMethod:@"POST" completionHandler:^(FBRequestConnection *connection,id result,
                                         NSError *error) {
        if (error)
        {
            [self failedToPublishPost];
        }
        else
        {
            [self finishedPublishingPost];
        }
        }];

您如何看待这个？