Ios UINavigationBar UIBABUTTONITEM在左侧有效，但在右侧无效

我的导航栏上有两个按钮。一个在左边，一个在右边。左边的按钮可用，但右边的按钮不可用。如果我交换按钮，重新编译并加载问题，无论哪个按钮位于栏的右侧位置，都使用右侧按钮保持

当我尝试使用右键时，左键也会停止工作

我如何使正确的按钮工作？下面是代码

UINavigationBar *NavBar = [[UINavigationBar alloc] init];
[NavBar sizeToFit];
[self.view addSubview:NavBar];
UIBarButtonItem *cmdBack = [[UIBarButtonItem alloc] initWithTitle:@"Back"
                                                            style:UIBarButtonItemStyleBordered
                                                           target:self
                                                           action:@selector(cmdBackClicked:)];
UIBarButtonItem *cmdAddDevice = [[UIBarButtonItem alloc] initWithTitle:@"Add Device"
                                                                 style:UIBarButtonItemStyleBordered
                                                                target:self
                                                                action:@selector(cmdAddDeviceClicked:)];
UINavigationItem *NavBarItems = [[UINavigationItem alloc] initWithTitle:@"Settings"];
NavBarItems.leftBarButtonItem = cmdBack;
NavBarItems.rightBarButtonItem = cmdAddDevice;
NavBar.items = [NSArray arrayWithObjects:NavBarItems, nil];

按钮的功能如下

- (void) cmdBackClicked:(id)sender
{
    [self.view removeFromSuperview];
}

- (void) cmdAddDeviceClicked:(id)sender
{
    vcAddDevice *ViewAddDevice = [[vcAddDevice alloc] initWithNibName:@"vcAddDevice"     bundle:nil];
    [ViewAddDevice SetEditDeviceMode:[NSString stringWithFormat:@"No"]];
   [self.view addSubview:ViewAddDevice.view];
}

在.h文件中，我有这个

#import <UIKit/UIKit.h>
#import "vcAddDevice.h"

@interface ViewControllerSettings : UIViewController<vcAddDeviceControllerDelegate, UITableViewDelegate, UITableViewDataSource>

- (IBAction) cmdBackClicked:(id) sender;
- (IBAction) cmdAddDeviceClicked:(id) sender;

@end

#导入
#导入“vcadDevice.h”
@界面ViewController设置：UIViewController
-（iAction）cmdBackClicked:（id）发件人；
-（iAction）cmdAddDeviceClicked:（id）发件人；
@结束