当我进行转换时，UITabBarController消失

Question

我的应用程序是基于UITabBarController的。 TestAppDelegate.h

@interface TestAppDelegate : NSObject <UIApplicationDelegate, UITabBarControllerDelegate>
{
    Facebook *facebook;
}

@property (nonatomic, retain) IBOutlet UIWindow *window;
@property (nonatomic, retain) IBOutlet UITabBarController *tabBarController;
@property (nonatomic, retain) Facebook *facebook;
@end

在FirstViewController中我写了这段代码

FormViewController *formViewController =[[FormViewController alloc]initWithNibName:@"FormViewController" bundle:nil];
formViewController.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;
[self presentModalViewController:formViewController animated:YES];

但是当视图转移到fromViewController时，tabBar就会破坏。