ios - iPhone/iPad的UILabel如何设置粗体和斜体？

Question

如何在iPhone/iPad的UILabel上设置粗斜体？ 我搜索了论坛，但没有任何帮助。谁能帮帮我？

Answer 1

不要尝试使用字体名称。使用字体描述符你不需要名字:

UILabel * label = [[UILabel alloc] init]; // use your label object instead of this
UIFontDescriptor * fontD = [label.font.fontDescriptor
            fontDescriptorWithSymbolicTraits:UIFontDescriptorTraitBold
                            | UIFontDescriptorTraitItalic];
label.font = [UIFont fontWithDescriptor:fontD size:0];

size:0 表示“保持大小不变​​”

使用 Swift 尝试以下扩展:

extension UIFont {

    func withTraits(traits:UIFontDescriptorSymbolicTraits...) -> UIFont {
        let descriptor = self.fontDescriptor()
            .fontDescriptorWithSymbolicTraits(UIFontDescriptorSymbolicTraits(traits))
        return UIFont(descriptor: descriptor, size: 0)
    }

    func boldItalic() -> UIFont {
        return withTraits(.TraitBold, .TraitItalic)
    }

}

那么你可以这样使用它:

myLabel.font = myLabel.font.boldItalic()

甚至添加其他特征，例如 Condensed:

myLabel.font = myLabel.font.withTraits(.TraitCondensed, .TraitBold, .TraitItalic)

Swift 4 更新:

extension UIFont {
  var bold: UIFont {
    return with(traits: .traitBold)
  } // bold

  var italic: UIFont {
    return with(traits: .traitItalic)
  } // italic

  var boldItalic: UIFont {
    return with(traits: [.traitBold, .traitItalic])
  } // boldItalic


  func with(traits: UIFontDescriptorSymbolicTraits) -> UIFont {
    guard let descriptor = self.fontDescriptor.withSymbolicTraits(traits) else {
      return self
    } // guard

    return UIFont(descriptor: descriptor, size: 0)
  } // with(traits:)
} // extension

如下使用:

myLabel.font = myLabel.font.bold

或

myLabel.font = myLabel.font.italic

或

myLabel.font = myLabel.font.with(traits: [ .traitBold, .traitCondensed ])

Swift 5 更新

extension UIFont {
    var bold: UIFont {
        return with(.traitBold)
    }

    var italic: UIFont {
        return with(.traitItalic)
    }

    var boldItalic: UIFont {
        return with([.traitBold, .traitItalic])
    }



    func with(_ traits: UIFontDescriptor.SymbolicTraits...) -> UIFont {
        guard let descriptor = self.fontDescriptor.withSymbolicTraits(UIFontDescriptor.SymbolicTraits(traits).union(self.fontDescriptor.symbolicTraits)) else {
            return self
        }
        return UIFont(descriptor: descriptor, size: 0)
    }

    func without(_ traits: UIFontDescriptor.SymbolicTraits...) -> UIFont {
        guard let descriptor = self.fontDescriptor.withSymbolicTraits(self.fontDescriptor.symbolicTraits.subtracting(UIFontDescriptor.SymbolicTraits(traits))) else {
            return self
        }
        return UIFont(descriptor: descriptor, size: 0)
    }
}