如何在rightBarButtonItem上添加更多的两个UIBarButtonItem？

YourViewontroller.h

UIView *view_navigation;

视图控制器

- (void)viewDidLoad
{
    view_navigation = [[UIView alloc]initWithFrame:CGRectMake(200, 5, 100, 40)];
    view_navigation.backgroundColor = [UIColor clearColor];

    UIButton *add_button =  [UIButton buttonWithType:UIButtonTypeCustom];
    [add_button setBackgroundImage:[UIImage imageNamed:@"Add-icon.png"] forState:UIControlStateNormal];
    [add_button addTarget:self action:@selector(Add_Student:) forControlEvents:UIControlEventTouchUpInside];
    [add_button.imageView setContentMode:UIViewContentModeScaleToFill];
    [add_button setFrame:CGRectMake(0, 8, 25, 25)];
    [view_navigation addSubview:add_button];


    UIButton *Remove_button =  [UIButton buttonWithType:UIButtonTypeCustom];
    [Remove_button setBackgroundImage:[UIImage imageNamed:@"Delete_icon.jpeg"] forState:UIControlStateNormal];
    [Remove_button addTarget:self action:@selector(Remove_Student:) forControlEvents:UIControlEventTouchUpInside];
    [Remove_button.imageView setContentMode:UIViewContentModeScaleToFill];
    [Remove_button setFrame:CGRectMake(40, 8, 25, 25)];
    [view_navigation addSubview:Remove_button];

    UIButton *Edit_button =  [UIButton buttonWithType:UIButtonTypeCustom];
    [Edit_button setBackgroundImage:[UIImage imageNamed:@"Edit_icon.jpeg"] forState:UIControlStateNormal];
    [Edit_button addTarget:self action:@selector(Edit_Student:) forControlEvents:UIControlEventTouchUpInside];
    [Edit_button.imageView setContentMode:UIViewContentModeScaleToFill];
    [Edit_button setFrame:CGRectMake(80, 8, 25, 25)];
    [view_navigation addSubview:Edit_button];


    [self.navigationController.navigationBar addSubview:view_navigation];


    [super viewDidLoad];
    // Do any additional setup after loading the view from its nib.
}
- (void)viewWillDisappear:(BOOL)animated
{
    [view_navigation removeFromSuperview];

    [super viewWillDisappear:animated];
}