objective-c – 在UISplitViewController中缺少UIBarButtonItem

我在UISplitViewController里面的右侧视图控制器中缺少带有popover的navigationItem.当我将iPad旋转到纵向时,只显示按钮.代码很好,我已经多次使用相同的(当然不是绝对的),但是现在我有这个奇怪的错误.

- (void)splitViewController:(UISplitViewController *)svc 
     willHideViewController:(UIViewController *)aViewController 
          withBarButtonItem:(UIBarButtonItem *)barButtonItem 
       forPopoverController:(UIPopoverController *)pc
{
    barButtonItem.title = aViewController.title;
    self.navigationItem.rightBarButtonItem = barButtonItem;
/*
this method gets called,class is set to be delegate of split view,barButtonItem && self.navigationItem are not nils.
*/
}

- (void)splitViewController:(UISplitViewController *)svc 
     willShowViewController:(UIViewController *)aViewController 
  invalidaTingBarButtonItem:(UIBarButtonItem *)button
{
    self.navigationItem.rightBarButtonItem = nil;
}

所有这些东西都是使用像这样的代码创建的……@H_607_10@

UISplitViewController *svc = [[UISplitViewController alloc] init];
UINavigationController *rightNav = [[UINavigationController alloc] init];
DetailViewController *dvc = [[DetailViewController alloc] initWithSomeArgs:args];
[rightNav pushViewController:dvc animated:NO];
svc.delegate = dvc;
svc.viewControllers = [NSArray arrayWithObjects:tabBarController,rightNav,nil]; 
// tabBar is good,not nil and working well on the iPhone
[self.window addSubview:svc.view];
[dvc release]; [rightNav release];

我不知道为什么这不起作用,我需要尽快弄明白.请帮帮我.@H_607_10@