在iOS7中自定义导航栏标题视图？

您好，我只想通过在iOS7中的导航栏上添加三个按钮来自定义导航栏的标题视图，下面是我的代码，但什么都没有发生

-(void)addCutomButtonsToNavigationController:(UINavigationController *)navigationController
{
    UIView *customNavigationTitleView=[[UIView alloc] initWithFrame:CGRectMake(20, 0, 250, 44)];
    [customNavigationTitleView setBackgroundColor:[UIColor blackColor]];

    UIButton *friendRequestButton=[UIButton buttonWithType:UIButtonTypeCustom];
    UIButton *messagesButton=[UIButton buttonWithType:UIButtonTypeCustom];
    UIButton *notificationsButton=[UIButton buttonWithType:UIButtonTypeCustom];

    [friendRequestButton setImage:[UIImage imageNamed:@"ic_clients.png"] forState:UIControlStateNormal];
    [messagesButton setImage:[UIImage imageNamed:@"ic_location.png"] forState:UIControlStateNormal];
    [notificationsButton setImage:[UIImage imageNamed:@"ic_message.png"] forState:UIControlStateNormal];

    [friendRequestButton setFrame:CGRectMake(0, 10, 40, 40)];

    [customNavigationTitleView addSubview:friendRequestButton];
    [customNavigationTitleView addSubview:messagesButton];
    [customNavigationTitleView addSubview:notificationsButton];

    navigationController.navigationItem.titleView =customNavigationTitleView;
}

试试这个

-(void)addCutomButtonsToNavigationController:(UINavigationController *)navigationController
{
    UIView *customNavigationTitleView=[[UIView alloc] initWithFrame:CGRectMake(40, 0, 160, 44)];

    UIButton *friendRequestButton=[UIButton buttonWithType:UIButtonTypeCustom];
    UIButton *messagesButton=[UIButton buttonWithType:UIButtonTypeCustom];
    UIButton *notificationsButton=[UIButton buttonWithType:UIButtonTypeCustom];

   [friendRequestButton setImage:[UIImage imageNamed:@"ic_clients.png"] forState:UIControlStateNormal];
   [messagesButton setImage:[UIImage imageNamed:@"ic_location.png"] forState:UIControlStateNormal];
   [notificationsButton setImage:[UIImage imageNamed:@"ic_messsage.png"] forState:UIControlStateNormal];

   [friendRequestButton setFrame:CGRectMake(10, 0, 40, 40)];
   [messagesButton setFrame:CGRectMake(60, 0, 40, 40)];
   [notificationsButton setFrame:CGRectMake(110, 0, 40, 40)];

   [customNavigationTitleView addSubview:friendRequestButton];
   [customNavigationTitleView addSubview:messagesButton];
   [customNavigationTitleView addSubview:notificationsButton];

   self.navigationItem.titleView =customNavigationTitleView;
}