未显示UIBarButtonItem

Question

我有一个名为"takeAction“的模态视图控制器。当模式视图控制器呈现给用户时，我正在尝试在takeAction中加载UIBarButtonItem。因此，UIBarButtonItem与模式视图控制器的内容是异步的。

但是这个按钮根本不存在。我该如何解决这个问题呢？

代码：

AppDelegate *delegate = [[UIApplication sharedApplication] delegate];
UINavigationController *navController = [delegate navController];
[navController presentModalViewController: takeAction animated:YES];

UIBarButtonItem *doneButton = [[UIBarButtonItem alloc] 
initWithBarButtonSystemItem:UIBarButtonItemStyleDone
target:self action:@selector(done)];

takeAction.navigationItem.rightBarButtonItem = doneButton;
[doneButton release];

Answer 1

UIBarButtonItem *doneButton = [[UIBarButtonItem alloc]initWithBarButtonSystemItem:UIBarButtonItemStyleDone target:self action:@selector(done)];

takeAction.navigationItem.rightBarButtonItem = doneButton ;
[doneButton release];

将上面的几行放到下面这一行：

UINavigationController *navController = [delegate navController]; 
[navController presentModalViewController: takeAction animated:YES];