尝试以编程方式创建 rightBarButtonItem

Question

这似乎不起作用。我做错了什么？

-(void)awakeFromNib{
    UIBarButtonItem *rightBarButtonItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemAdd target:self action:@selector(showNewEventViewController)];
    self.navigationItem.rightBarButtonItem = rightBarButtonItem;
    NSLog(@"awaked");
    [rightBarButtonItem release];
}

Answer 1

我的猜测是，您将 UIBarButtonItem 添加到了错误的对象！
您需要将其添加到 rootViewController （而不是像您可能所做的那样添加到 UINavigationController ）

YourRootViewController *theRootController = [[YourRootViewController alloc] init];

UINavigationController* navContainer = [[UINavigationController alloc] initWithRootViewController:theRootController];

UIBarButtonItem *btnCancel = [[UIBarButtonItem alloc] initWithTitle:@"Cancel" style:UIBarButtonItemStyleBordered target:self action:@selector(dismiss)];    
theRootController.navigationItem.rightBarButtonItem = btnCancel

[navContainer setModalTransitionStyle:UIModalTransitionStyleCrossDissolve];
[self presentModalViewController:navContainer animated:YES];

Answer 2

我通常会将此代码放在 viewDidLoad 方法中，而不是 awakeFromNib 方法中；我不确定这是否是你的问题所在。 “不工作”是什么意思？

Answer 3

试试这个：

- (void) initUI {   
   UIBarButtonItem *btnCancel = [[[UIBarButtonItem alloc] initWithTitle:@"Cancel" 
                                  style:UIBarButtonItemStyleBordered 
                                  target:self 
                                  action:@selector(dismiss)]autorelease];    

   self.navigationItem.rightBarButtonItem = btnCancel;

   //[btnCancel release]; no need to explicitly release the item

}