如何获取UILabel的重量？

Question

用户可以通过Storyboard或编程方式设置字体的粗细，如常规、半粗等。

我想读取任何字体标签的字重。

我尝试了po label.font.description，字重也在那里，但没有外部变量可以获取字体的字重。

这可行吗？

- Lalit Kumar

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label.font.UIFontWeight - Cy-4AH

我认为不可能获取字体的重量，你只能检查它是否加粗。 - Prashant Tukadiya

也许这个会有用：-https://developer.apple.com/documentation/uikit/uifontdescriptor.traitkey - AshvinGudaliya

Answer 1

看起来 fontDescriptor.fontAttributes 不会返回字体的所有属性。幸运的是，fontDescriptor.object(forKey: .traits) 可以返回所有属性，所以我们可以使用这个方法。

extension UIFont {
    var weight: UIFont.Weight {
        guard let weightNumber = traits[.weight] as? NSNumber else { return .regular }
        let weightRawValue = CGFloat(weightNumber.doubleValue)
        let weight = UIFont.Weight(rawValue: weightRawValue)
        return weight
    }

    private var traits: [UIFontDescriptor.TraitKey: Any] {
        return fontDescriptor.object(forKey: .traits) as? [UIFontDescriptor.TraitKey: Any]
            ?? [:]
    }
}

然后，它就像 label.font.weight 这样简单。

（这与 https://dev59.com/_6jka4cB1Zd3GeqPFuSs#48688000 原理上是等价的，但它使用了 UIKit 的API）

- DeFrenZ

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优雅。我在扩展中添加了一个变量，用于将IB定义的系统字体转换为其等宽数字等效字体，这是我一直在努力解决的问题。谢谢。无法在此处编写代码，但核心内容是：return UIFont.monospacedDigitSystemFont(ofSize: self.pointSize, weight: self.weight)。 - JLundell

Answer 2

要获取字体的加粗程度字符串名称，使用字体描述符并传递face属性。

Swift 4.2

let font = UIFont.systemFont(ofSize: 14, weight: UIFont.Weight.bold)
let face = font.fontDescriptor.object(forKey: UIFontDescriptorFaceAttribute) as! String
print("face: \(face)")

Swift 3

let font = UIFont.systemFont(ofSize: 14, weight: UIFontWeightBold)
let face = font.fontDescriptor.object(forKey: UIFontDescriptorFaceAttribute) as! String
print("face: \(face)")

- bbarnhart

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UIFontDescriptorFaceAttribute在Swift的较新版本中已更名为UIFontDescriptor.AttributeName.face（或简写为.face）。 - Dafydd Williams

Answer 3

尝试使用Swift 4编写以下示例字体扩展（它需要改进以适用于所有字重类型）

extension UIFont {

    func getFontWeight() -> UIFont.Weight {
    
        let fontAttributeKey = UIFontDescriptor.AttributeName.init(rawValue: "NSCTFontUIUsageAttribute")
        if let fontWeight = self.fontDescriptor.fontAttributes[fontAttributeKey] as? String {
            switch fontWeight {

            case "CTFontBoldUsage":
                return UIFont.Weight.bold
        
            case "CTFontBlackUsage":
                return UIFont.Weight.black
        
            case "CTFontHeavyUsage":
                return UIFont.Weight.heavy
        
            case "CTFontUltraLightUsage":
                return UIFont.Weight.ultraLight
        
            case "CTFontThinUsage":
                return UIFont.Weight.thin
        
            case "CTFontLightUsage":
                return UIFont.Weight.light
        
            case "CTFontMediumUsage":
                return UIFont.Weight.medium
        
            case "CTFontDemiUsage":
                return UIFont.Weight.semibold
        
            case "CTFontRegularUsage":
                return UIFont.Weight.regular

            default:
                return UIFont.Weight.regular
            }
        }
        
    return UIFont.Weight.regular
}

尝试使用标签：

let label = UILabel()
var fontWeight = label.font.getFontWeight()
print("fontWeight - \(fontWeight)")

label.font = UIFont.systemFont(ofSize: 14, weight: UIFont.Weight.bold)
fontWeight = label.font.getFontWeight()
print("fontWeight - \(fontWeight)")

label.font = UIFont.systemFont(ofSize: 14, weight: UIFont.Weight.black)
fontWeight = label.font.getFontWeight()
print("fontWeight - \(fontWeight)")

label.font = UIFont.systemFont(ofSize: 14, weight: UIFont.Weight.heavy)
fontWeight = label.font.getFontWeight()
print("fontWeight - \(fontWeight)")

label.font = UIFont.systemFont(ofSize: 14, weight: UIFont.Weight.ultraLight)
fontWeight = label.font.getFontWeight()
print("fontWeight - \(fontWeight)")

label.font = UIFont.systemFont(ofSize: 14, weight: UIFont.Weight.thin)
fontWeight = label.font.getFontWeight()
print("fontWeight - \(fontWeight)")

label.font = UIFont.systemFont(ofSize: 14, weight: UIFont.Weight.light)
fontWeight = label.font.getFontWeight()
print("fontWeight - \(fontWeight)")

label.font = UIFont.systemFont(ofSize: 14, weight: UIFont.Weight.medium)
fontWeight = label.font.getFontWeight()
print("fontWeight - \(fontWeight)")

label.font = UIFont.systemFont(ofSize: 14, weight: UIFont.Weight.semibold)
fontWeight = label.font.getFontWeight()
print("fontWeight - \(fontWeight)")

这是苹果文档，其中包含字体粗细列表。

此权重的值是NSNumber对象。有效值范围为-1.0至1.0。值为0.0对应于常规或中等字体重量。您还可以使用字体重量常数来指定特定的重量。

- Krunal

Answer 4

看起来没有直接的方法可以获得它。作为一种解决方案，您可以按如下方式获取字体的重量指示：

let labelFont = label.font as CTFont
if let fontTraits = CTFontCopyTraits(labelFont) as? [CFString: CFNumber], let fontWeight = fontTraits[kCTFontWeightTrait] {
    print(fontWeight)
}

UIFont已被转换为CTFont，通过使用CTFontCopyTraits(_:)生成CFDictionary（包含kCTFontWeightTrait的值）。请注意，它可能无法确定确切的字体重量，但对于指示重量可能有所帮助：

从字体特征字典中访问标准化权重特征的关键字。返回的值是表示标准化权重的-1.0到1.0之间的浮点值的CFNumber。值0.0对应于常规或中等字体重量。

- Ahmad F

Answer 5

你可以尝试调整字体的符号特征:

// is true when font is bold
label.font.fontDescriptor.symbolicTraits.contains(UIFontDescriptorSymbolicTraits.traitBold)

查看文档以获取更多特征。

- Milan Nosáľ

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当我检查粗体和斜体样式时，这个是有效的。但是对于半粗体，没有UIFontDescriptorSymbolicTraits。 - Kumar