Navigation item

   UIButton *btn=[[UIButton alloc]init];

    btn.frame = CGRectMake(0, 0, 40, 20);
    btn.backgroundColor = [UIColor redColor];
    
    
    UIButton *btn2=[[UIButton alloc]init];
    btn2.frame = CGRectMake(0, 0, 40, 20);

    btn2.backgroundColor = [UIColor blueColor];
    
    设置按钮的背景图片（默认/高亮）
   [btn setBackgroundImage:[UIImage imageWithName:ImageName] forState:UIControlStateNormal];
[btn setBackgroundImage:[UIImage imageWithName:highImageName] forState:UIControlStateHighlighted];
    
    设置按钮的尺寸和图片一样大，使用了UIImage的分类

    [btn addTarget:self action:@"close" forControlEvents:UIControlEventTouchUpInside];
    
      UIBarButtonItem *btnItem1 =   [[UIBarButtonItem alloc]initWithCustomView:btn];
    
      UIBarButtonItem *btnItem2 =   [[UIBarButtonItem alloc]initWithCustomView:btn2]; //显示右边的按钮
    

    self.navigationItem.leftBarButtonItem = btnItem1;//ok
    self.navigationItem.hidesBackButton = YES; //隐藏左边的返回按钮
    self.navigationItem.leftBarButtonItem = nil; //仍然显示返回
    self.navigationItem.rightBarButtonItem = btnItem2;//ok