// NO.1，using Image note:recommended.推荐方式
   // set the bar shadow image
   // without shadow : use -[[CYLTabBarController hideTabBarShadowImageView] in CYLMainRootViewController.m
   if (@available(iOS 13.0, *)) {
       UITabBarItemAppearance *inlineLayoutAppearance = [[UITabBarItemAppearance  alloc] init];
       // set the text Attributes
       // 设置文字属性
       [inlineLayoutAppearance.normal setTitleTextAttributes:normalAttrs];
       [inlineLayoutAppearance.selected setTitleTextAttributes:selectedAttrs];
   
       UITabBarAppearance *standardAppearance = [[UITabBarAppearance alloc] init];
       standardAppearance.stackedLayoutAppearance = inlineLayoutAppearance;
       standardAppearance.backgroundColor = [UIColor cyl_systemBackgroundColor];
       standardAppearance.shadowImage = [[self class] imageWithColor:[UIColor cyl_systemGreenColor] size:CGSizeMake([UIScreen mainScreen].bounds.size.width, 1)];
       self.tabBar.standardAppearance = standardAppearance;
   } else {
       // Override point for customization after application launch.
       // set the text Attributes
       // 设置文字属性
       UITabBarItem *tabBar = [UITabBarItem appearance];
       [tabBar setTitleTextAttributes:normalAttrs forState:UIControlStateNormal];
       [tabBar setTitleTextAttributes:selectedAttrs forState:UIControlStateSelected];
       
//        // This shadow image attribute is ignored if the tab bar does not also have a custom background image.So at least set somthing.
       [[UITabBar appearance] setBackgroundImage:[[UIImage alloc] init]];
       [[UITabBar appearance] setShadowImage:[[self class] imageWithColor:[UIColor cyl_systemGreenColor] size:CGSizeMake([UIScreen mainScreen].bounds.size.width, 1)]];
   }

-[[CYLTabBarController hideTabBarShadowImageView]