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

Question

以下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 在您 select 时保留其大字体：

    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
    }

但是当你在 UITabBar 外观代理上设置 UITabBarAppearance 时，当你 select 标签时字体大小被破坏：

    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 UITabBarAppearance 会破坏 setTitleTextAttributes 字体大小选择？

背景资料：

我在 UITabBar 上设置 standardAppearance 的原因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，而不是新的会在屏幕上没有内容时变为透明（并弄乱应用程序设计）。

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，我找到了解决方法（有点感觉我现在只是在使用 Stack Overflow rubber duck）。

以下选择标签后将保留正确的字体大小。

请注意，仍然需要直接在 UITabBarItem（UITabBarItem.appearance().setTitleTextAttributes... 行）上设置属性，否则选项卡不会以正确的字体大小开头，它们只会更改被用户选择后。

另请注意，如果您在选项卡栏上设置 standardAppearance，您可能还想设置 scrollEdgeAppearance - 正如我在原始代码的最后一段中所做的那样问题。

    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
    }

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

Setting a UITabBarAppearance breaks UITabBarItem appearance proxy font size when selecting tabs

uikit

uitabbar

ios

uiappearance

swift