选择选项卡时，设置 UITabBarAppearance 会破坏 UITabBarItem 外观代理字体大小

Question

以下内容将标题文本外观代理设置为使用大字体，按预期工作，并且UITabBarItem当您选择它们​​时， s 会保留其大字体：

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        
        // UITabBar.appearance().standardAppearance = UITabBarAppearance()
                
        let bigFont = UIFont.systemFont(ofSize: 20)
        UITabBarItem.appearance().setTitleTextAttributes([NSAttributedString.Key.font: bigFont], for: .normal)
        UITabBarItem.appearance().setTitleTextAttributes([NSAttributedString.Key.font: bigFont], for: .selected)
        
        return true
    }

UITabBarAppearance但是，当您在外观代理上设置 a 时UITabBar，选择选项卡时字体大小会被破坏：

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        
        UITabBar.appearance().standardAppearance = UITabBarAppearance()
                
        let bigFont = UIFont.systemFont(ofSize: 20)
        UITabBarItem.appearance().setTitleTextAttributes([NSAttributedString.Key.font: bigFont], for: .normal)
        UITabBarItem.appearance().setTitleTextAttributes([NSAttributedString.Key.font: bigFont], for: .selected)
        
        return true
    }

问题：

有谁知道为什么设置 aUITabBarAppearance会破坏setTitleTextAttributes字体大小选择？

背景资料：

standardAppearance我使用设置的原因UITabBar是因为在我的实际项目中，我使用以下代码来保留选项卡栏的旧外观，而不是当屏幕上没有内容时变为透明的新外观（并搞乱了应用程序设计）。

如果有一种方法可以在不破坏字体大小的情况下实现这一点，那么这可能是一个潜在的“修复”:)

if #available(iOS 13.0, *) {
    let tabBarAppearance = UITabBarAppearance()
    tabBarAppearance.configureWithDefaultBackground()
    UITabBar.appearance().standardAppearance = tabBarAppearance
    if #available(iOS 15.0, *) {
        UITabBar.appearance().scrollEdgeAppearance = tabBarAppearance
    }
}

Answer 1

好吧，我找到了一个解决方案（有点感觉我此时只是使用 Stack Overflow 来橡皮鸭）。

以下将在选择选项卡后保留正确的字体大小。

UITabBarItem请注意，仍然需要直接在（线条）上设置属性UITabBarItem.appearance().setTitleTextAttributes...，因为否则选项卡将不会以正确的字体大小开始，它们只会在用户选择后才会更改为正确的字体大小。

另请注意，如果您在选项卡栏上设置standardAppearance，您可能还需要设置scrollEdgeAppearance- 就像我在原始问题的最后一个代码片段中所做的那样。

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        
        let bigFont = UIFont.systemFont(ofSize: 20)
        let textAttributes = [NSAttributedString.Key.font: bigFont]
        
        UITabBarItem.appearance().setTitleTextAttributes(textAttributes, for: .normal)
        UITabBarItem.appearance().setTitleTextAttributes(textAttributes, for: .selected)
        
        let tabBarItemAppearance = UITabBarItemAppearance()
        tabBarItemAppearance.normal.titleTextAttributes = textAttributes
        tabBarItemAppearance.selected.titleTextAttributes = textAttributes
        
        let tabBarAppearance = UITabBarAppearance()
        tabBarAppearance.inlineLayoutAppearance = tabBarItemAppearance
        tabBarAppearance.stackedLayoutAppearance = tabBarItemAppearance
        tabBarAppearance.compactInlineLayoutAppearance = tabBarItemAppearance
        
        UITabBar.appearance().standardAppearance = tabBarAppearance
        
        return true
    }