UIBarAppearance

UIBarAppearance提供两个子类：UITabBarAppearance、UINavigationBarAppearance

一、UITabBarAppearance

func setAppearance() {
    tabBar.isTranslucent = false//不透明
    tabBar.backgroundColor = UIColor.white
    //barTintColor = UIColor.blue //bar背景颜色
    tabBar.tintColor = UIColor.yellow//icont颜色

    if #available(iOS 13.0, *) {
        //系统外观
        //let itemAppearance =  UITabBarItemAppearance(style: .stacked)
        //自定义外观：图标、文字、徽章
        let itemAppearance =  UITabBarItemAppearance(style: .stacked)
        itemAppearance.normal.titleTextAttributes = [NSAttributedString.Key.foregroundColor : UIColor.purple]
        itemAppearance.selected.titleTextAttributes = [NSAttributedString.Key.foregroundColor : UIColor.red]
        itemAppearance.normal.iconColor = UIColor.blue
        itemAppearance.selected.iconColor = UIColor.red
        itemAppearance.normal.badgeBackgroundColor = UIColor.green
        itemAppearance.normal.badgeTextAttributes = [NSAttributedString.Key.foregroundColor : UIColor.red]

        let appearance = UITabBarAppearance()
        /* 没有设置时，系统是会提供默认配置的。
         * stackedLayoutAppearance：tabarItem文字、图片垂直排布布局时的外观。一般iPhone竖屏时都是这样的。
         * inlineLayoutAppearance： 文字、图片并列排布时的外观。例如iPad的tabar都是并列排布的。
         * compactInlineLayoutAppearance： 文字、图片并列排布显示，Size Class为compact环境下的外观。比如 iphone8 tabar在横屏时，文字、图片是并列排布的，size class 为compact width ,compact height。
         */
        appearance.stackedLayoutAppearance = itemAppearance
        appearance.compactInlineLayoutAppearance = itemAppearance;
        appearance.inlineLayoutAppearance = itemAppearance;

        tabBar.standardAppearance = appearance;

        if #available(iOS 15.0, *) {
            //当可滚动视图的内容边缘与tabar对齐时,所呈现的外观。而standardAppearance现在就是正常情况的外观。
            //当属性值是nil时，UIKit 将会使用standardAppearance来配置tabar的外观，并将会修改tar的背景为透明背景。
            tabBar.scrollEdgeAppearance = appearance;
        }
    }
}

二、UINavigationBarAppearance

class NavigationController: UINavigationController {

    override func viewDidLoad() {
        super.viewDidLoad()

        if #available(iOS 13.0, *) {
            //不透明
            self.navigationBar.isTranslucent = false

            let barAppearance = UINavigationBarAppearance()
            //标题颜色、字体
            barAppearance.titleTextAttributes = [NSAttributedString.Key.foregroundColor: UIColor.red]
            barAppearance.titleTextAttributes = [NSAttributedString.Key.font: UIFont.systemFont(ofSize: 30)]
            // 下横线颜色
            barAppearance.shadowColor = UIColor.red
            barAppearance.backgroundColor = UIColor.white

            // 按钮样式\完成按钮、返回按钮
            barAppearance.buttonAppearance = setAppearance(UIColor.red, 25)
            barAppearance.doneButtonAppearance = setAppearance(UIColor.purple, 25)
            barAppearance.backButtonAppearance = setAppearance(UIColor.yellow, 25)

            navigationBar.standardAppearance = barAppearance
            navigationBar.scrollEdgeAppearance = barAppearance
            //item字体颜色
            navigationBar.tintColor = UIColor.red

            if #available(iOS 15.0, *) {
                navigationBar.compactScrollEdgeAppearance = barAppearance
            }
        }
    }

    @available(iOS 13.0, *)
    func setAppearance(_ color: UIColor, _ font: CGFloat) -> UIBarButtonItemAppearance {
        let itemAppearance = UIBarButtonItemAppearance()
        itemAppearance.normal.titleTextAttributes = [NSAttributedString.Key.font: UIFont.systemFont(ofSize: font)]
        //尝试改变前景颜色，但发现没有发生任何变化。（改用navigationBar.tintColor = UIColor.red）
        //itemAppearance.normal.titleTextAttributes = [NSAttributedString.Key.foregroundColor: color]
        return itemAppearance
    }

}