MBProgressHUD无效

Question

我的NavigationController中的RootViewController有一个UIButton。单击此按钮时，某些数据将从服务器加载，最后会出现一个新视图。这可能需要几秒钟，因此我想在此期间显示MBProgressHUD以向用户显示正在发生的事情。但它不起作用。

加载数据并显示HUD，所有这些都发生在我的prepareForSegue-Method中，它看起来像这样：

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{

     if([segue.identifier isEqualToString:@"showAllPoints"])
     {
         HUD = [[MBProgressHUD alloc] initWithView:self.navigationController.view];
         HUD.labelText = @"Loading data";
         HUD.detailsLabelText = @"Please wait...";
         HUD.mode = MBProgressHUDModeAnnularDeterminate;
         [self.navigationController.view addSubview:HUD];

         [HUD showWhileExecuting:@selector(prepareJSONData:) 
              onTarget:self withObject:        
         [self getJSONData] animated:YES];

         [self prepareJSONData:[self getJSONData]];
         [segue.destinationViewController setPoints:pointsArray];
    }

}

没有任何事情发生，所以我们错了吗？有什么问题？

编辑： 以下是方法getJSON和prepareJSONData：

-(NSData *)getJSONData
{
  NSURL *url = [NSURL URLWithString:@"http://www.example.de/example.php"];

  NSMutableURLRequest *request = [[NSMutableURLRequest alloc] init];
  [request setURL:url];
  [request setHTTPMethod:@"POST"];

  [request setValue:@"application/json" forHTTPHeaderField:@"Content-Type"];

  NSError *error;
  NSURLResponse *response;

  NSData *urlData=[NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];

return urlData;
}


-(void)prepareJSONData:(NSData *)jsonData
{
  NSError *error;

  NSDictionary *wholeDict = [NSJSONSerialization JSONObjectWithData:jsonData options:NSJSONReadingMutableContainers error:&error];

  allWutpunkteArray = [wholeDict objectForKey:@"points"];

 }

Answer 1

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
    {

         if([segue.identifier isEqualToString:@"showAllPoints"])
         {
             HUD = [[MBProgressHUD alloc] initWithView:self.navigationController.view];
             HUD.labelText = @"Loading data";
             HUD.detailsLabelText = @"Please wait...";
             HUD.mode = MBProgressHUDModeAnnularDeterminate;
             [self.navigationController.view addSubview:HUD];
             [HUD showWhileExecuting:@selector(prepareJSONData:[self getJSONData]) 
                  onTarget:self withObject:        
             nil animated:YES];
             [segue.destinationViewController setPoints:pointsArray];
        }

    }

希望这会有所帮助......