将UIBarButtonItem添加到推送到UINavigation控制器上的UIViewController

Question

我试图将UIViewController推送到导航控制器上，然后将UIBarButtonItem添加到导航栏中，以便我可以使用它来显示倒数计时器。

UINavigationController *navController = [[Session sharedInstance] getNavigationController]; 
GamePlayViewController *gameController = [[GamePlayViewController alloc] initWithNibName:@"GamePlayViewController" bundle:nil ]; 

UIBarButtonItem *timerBtn = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemFlexibleSpace target:nil action:nil]; 

gameController.navigationItem.rightBarButtonItems = [NSArray arrayWithObjects:timerBtn, nil]; 

[navController pushViewController:gameController animated:YES]; 

当我使用上面的代码不起作用。我也尝试从控制器本身的ViewDidload方法做到这一点，但没有骰子。我甚至尝试使用rightBarButtonItem却得到一个错误，说明

"to uncaught exception 'NSInvalidArgumentException', reason: 'Fixed and flexible space items not allowed as individual navigation bar button item. Please use the leftBarButtonItems (that's plural) property.' 
*** First throw call stack:" 




UIBarButtonItem *timerBtn = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemFlexibleSpace target:nil action:nil]; 

self.navigationItem.rightBarButtonItem = timerBtn; 

Answer 1

如果你去IB并尝试添加一个灵活的空间或固定的空间，你会看到这两个对象，指出这2只能在细节被添加到正在添加到UIToolBar的UIBarButtonItem中，而不是添加到导航栏！

因此，我建议你改变你的代码下面下手：

UIBarButtonItem *timerBtn = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonItemStylePlain target:nil action:nil];