想要在navigation controller 的頂端條添加一個刷新鍵。不知道為什么不執行。hearder代碼：@interface PropertyViewController : UINavigationController {}添加button代碼：(id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil { if (self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]) {    UIBarButtonItem *anotherButton = [[UIBarButtonItem alloc] initWithTitle:@"Show" style:UIBarButtonItemStylePlain            target:self action:@selector(refreshPropertyList:)];    self.navigationItem.rightBarButtonItem = anotherButton; } return self; } 不知道錯誤在哪兒