iOS使用Method Swizzling替换系统字体：Xib视图不生效求助

阿华AIGC实验室

2026-5-6

解决Xib/Storyboard中系统字体未被Method Swizzling替换的问题

这个问题我之前也踩过坑！核心原因是：Xib/Storyboard加载控件时，并不是直接调用你Swizzle的那些systemFont(ofSize:)类方法，而是通过UIFontDescriptor这条路径初始化字体——系统先创建对应系统字体的描述符，再用UIFont(descriptor:size:)生成字体对象，这部分你没做拦截，所以Xib里的字体没被替换。

下面是不用修改任何Xib的完整解决方案：

1. 补充Swizzle UIFont的初始化方法

我们需要拦截init(descriptor:size:)这个实例初始化方法，在里面把系统字体的描述符替换成自定义字体的描述符，同时保留原字体的字重、样式等属性。

修改你的UIFont扩展代码如下：

import UIKit
import ObjectiveC

extension UIFont {
    static let setSystemFont: Void = {
        // 保留你原来的所有类方法Swizzle代码
        let m1 = class_getClassMethod(UIFont.self, #selector(systemFont(ofSize:)))!
        let m2 = class_getClassMethod(UIFont.self, #selector(customFont(ofSize:)))!
        method_exchangeImplementations(m1, m2)
        
        let m3 = class_getClassMethod(UIFont.self, #selector(preferredFont(forTextStyle:)))!
        let m4 = class_getClassMethod(UIFont.self, #selector(customFont(forTextStyle:)))!
        method_exchangeImplementations(m3, m4)
        
        let m5 = class_getClassMethod(UIFont.self, #selector(boldSystemFont(ofSize:)))!
        let m6 = class_getClassMethod(UIFont.self, #selector(boldCustomFont(ofSize:)))!
        method_exchangeImplementations(m5, m6)
        
        let m7 = class_getClassMethod(UIFont.self, #selector(italicSystemFont(ofSize:)))!
        let m8 = class_getClassMethod(UIFont.self, #selector(italicCustomFont(ofSize:)))!
        method_exchangeImplementations(m7, m8)
        
        let m9 = class_getClassMethod(UIFont.self, #selector(systemFont(ofSize:weight:)))!
        let m10 = class_getClassMethod(UIFont.self, #selector(customFont(ofSize:weight:)))!
        method_exchangeImplementations(m9, m10)
        
        let m11 = class_getClassMethod(UIFont.self, #selector(preferredFont(forTextStyle:compatibleWith:)))!
        let m12 = class_getClassMethod(UIFont.self, #selector(customFont(forTextStyle:compatibleWith:)))!
        method_exchangeImplementations(m11, m12)
        
        // 新增：Swizzle 实例初始化方法
        let initMethod = class_getInstanceMethod(UIFont.self, #selector(UIFont.init(descriptor:size:)))!
        let customInitMethod = class_getInstanceMethod(UIFont.self, #selector(UIFont.customInit(descriptor:size:)))!
        method_exchangeImplementations(initMethod, customInitMethod)
    }()
}

private extension UIFont {
    // 改造原有自定义字体方法，加入语言判断和安全降级
    @objc class func customFont(ofSize fontSize: CGFloat) -> UIFont {
        let targetFont = preferredFontNameForCurrentLanguage()
        return UIFont(name: targetFont, size: fontSize) ?? UIFont.systemFont(ofSize: fontSize)
    }
    
    @objc class func customFont(forTextStyle style: UIFont.TextStyle) -> UIFont {
        let fontSize = UIFont.preferredFont(forTextStyle: style).pointSize
        let targetFont = preferredFontNameForCurrentLanguage()
        return UIFont(name: targetFont, size: fontSize) ?? UIFont.preferredFont(forTextStyle: style)
    }
    
    @objc class func boldCustomFont(ofSize fontSize: CGFloat) -> UIFont {
        let targetFont = "\(preferredFontNameForCurrentLanguage())-Bold"
        return UIFont(name: targetFont, size: fontSize) ?? UIFont.boldSystemFont(ofSize: fontSize)
    }
    
    @objc class func italicCustomFont(ofSize fontSize: CGFloat) -> UIFont {
        let targetFont = "\(preferredFontNameForCurrentLanguage())-Italic"
        return UIFont(name: targetFont, size: fontSize) ?? UIFont.italicSystemFont(ofSize: fontSize)
    }
    
    @objc class func customFont(ofSize fontSize: CGFloat, weight: UIFont.Weight) -> UIFont {
        var targetFont = preferredFontNameForCurrentLanguage()
        switch weight {
        case .bold: targetFont += "-Bold"
        case .italic: targetFont += "-Italic"
        default: break
        }
        return UIFont(name: targetFont, size: fontSize) ?? UIFont.systemFont(ofSize: fontSize, weight: weight)
    }
    
    @objc class func customFont(forTextStyle style: UIFont.TextStyle, compatibleWith traitCollection: UITraitCollection?) -> UIFont {
        let fontSize = UIFont.preferredFont(forTextStyle: style, compatibleWith: traitCollection).pointSize
        let targetFont = preferredFontNameForCurrentLanguage()
        return UIFont(name: targetFont, size: fontSize) ?? UIFont.preferredFont(forTextStyle: style, compatibleWith: traitCollection)
    }
    
    // 新增：拦截初始化方法，替换系统字体描述符
    @objc convenience init(customInit descriptor: UIFontDescriptor, size: CGFloat) {
        // 先调用原初始化方法（Swizzle后，这里的customInit指向原init方法）
        self.init(customInit: descriptor, size: size)
        
        // 只替换系统字体的描述符
        guard descriptor.fontAttributes[.family] as? String == UIFont.systemFontFamilyName else {
            return
        }
        
        // 根据当前语言获取目标字体
        let targetFont = preferredFontNameForCurrentLanguage()
        var newAttributes = descriptor.fontAttributes
        newAttributes[.family] = targetFont
        
        // 匹配原字体的字重
        if let traits = newAttributes[.traits] as? [UIFontDescriptor.TraitKey: Any],
           let weightValue = traits[.weight] as? CGFloat {
            switch weightValue {
            case UIFont.Weight.bold.rawValue:
                newAttributes[.family] = "\(targetFont)-Bold"
            case UIFont.Weight.italic.rawValue:
                newAttributes[.family] = "\(targetFont)-Italic"
            default: break
            }
        }
        
        // 替换为自定义字体描述符
        let customDescriptor = UIFontDescriptor(fontAttributes: newAttributes)
        if let finalFont = UIFont(descriptor: customDescriptor, size: size) {
            self = finalFont
        }
    }
    
    // 新增：根据当前语言返回对应字体名
    private static func preferredFontNameForCurrentLanguage() -> String {
        let languageCode = Locale.current.languageCode ?? "en"
        switch languageCode {
        case "zh", "zh-Hans", "zh-Hant":
            return "PingFangSC-Regular" // 中文用苹方
        case "ja":
            return "HiraginoSans-W3" // 日文用冬青黑体
        default:
            return "Chalkduster" // 其他语言用测试字体
        }
    }
}