在NavigationBar上设置rightbutton的示例代码.
UIBarButtonItem *rightButton = [[UIBarButtonItem alloc] initWithTitle:@"Done"
style:UIBarButtonItemStyleDone target:nil action:nil];
UINavigationItem *item = [[UINavigationItem alloc] initWithTitle:@"Title"];
item.rightBarButtonItem = rightButton;
item.hidesBackButton = YES;
[bar pushNavigationItem:item animated:NO];
但通常情况下，你会得到NavigationController分，这样你就可以写道:
UIBarButtonItem *rightButton = [[UIBarButtonItem alloc] initWithTitle:@"Done"
style:UIBarButtonItemStyleDone target:nil action:nil];
self.navigationItem.rightBarButtonItem = rightButton;