ios - 如何获得符合辅助功能设置的等宽字体

Question

let bodyFontDescriptor = UIFontDescriptor
    .preferredFontDescriptor(withTextStyle: UIFontTextStyle.body)
let bodyMonospacedFontDescriptor = bodyFontDescriptor.addingAttributes(
    [
        UIFontDescriptorFeatureSettingsAttribute: [
            [
                UIFontFeatureTypeIdentifierKey: kTextSpacingType,
                UIFontFeatureSelectorIdentifierKey: kMonospacedTextSelector
            ]
        ]
    ])
let bodyMonospacedFont = UIFont(descriptor: bodyMonospacedFontDescriptor, size: 0.0)
textview.font = bodyMonospacedFont

这会生成具有可变宽度字符的文本。 我需要在没有硬编码 courier new 的情况下获得等宽字体 和固定尺寸。 部署目标是ios 9.0

Answer 1

这是 UIFontDescriptor 的扩展，它返回给定文本样式的首选等宽字体描述符。没有使用 UIFont 或 UIFontDescriptor 获得完全等宽字体的简单方法。此解决方案尝试找到一个好的等宽字体，并在需要时回退到 Courier。

extension UIFontDescriptor {
    static let monoDescriptor: UIFontDescriptor = {
        // Attempt to find a good monospaced, non-bold, non-italic font
        for family in UIFont.familyNames {
            for name in UIFont.fontNames(forFamilyName: family) {
                let f = UIFont(name: name, size: 12)!
                let fd = f.fontDescriptor
                let st = fd.symbolicTraits
                if st.contains(.traitMonoSpace) && !st.contains(.traitBold) && !st.contains(.traitItalic) && !st.contains(.traitExpanded) && !st.contains(.traitCondensed) {
                    return fd
                }
            }
        }

        return UIFontDescriptor(name: "Courier", size: 0) // fallback
    }()

    class func preferredMonoFontDescriptor(withTextStyle style: UIFontTextStyle) -> UIFontDescriptor {
        // Use the following line if you need a fully monospaced font
        let monoDescriptor = UIFontDescriptor.monoDescriptor

        // Use the following two lines if you only need monospaced digits in the font
        //let monoDigitFont = UIFont.monospacedDigitSystemFont(ofSize: 0, weight: .regular)
        //let monoDescriptor = monoDigitFont.fontDescriptor

        // Get the non-monospaced preferred font
        let defaultFontDescriptor = preferredFontDescriptor(withTextStyle: style)
        // Remove any attributes that specify a font family or name and remove the usage
        // This will leave other attributes such as size and weight, etc.
        var fontAttrs = defaultFontDescriptor.fontAttributes
        fontAttrs.removeValue(forKey: .family)
        fontAttrs.removeValue(forKey: .name)
        fontAttrs.removeValue(forKey: .init(rawValue: "NSCTFontUIUsageAttribute"))
        let monospacedFontDescriptor = monoDescriptor.addingAttributes(fontAttrs)

        return monospacedFontDescriptor.withSymbolicTraits(defaultFontDescriptor.symbolicTraits) ?? monospacedFontDescriptor
    }
}

请注意有关您是需要完全等宽字体还是仅具有等宽数字的字体的注释。注释/取消注释这些行以满足您的特定需求。

示例用法:

let bodyMonospacedFont = UIFont(descriptor: .preferredMonoFontDescriptor(withTextStyle: .body), size: 0)
textview.font = bodyMonospacedFont

以下是一些测试代码，用于确认 preferredMonoFontDescriptor(withTextStyle:) 的结果适用于所有样式:

let textStyles: [UIFontTextStyle] = [ .body, .callout, .caption1, .caption2, .footnote, .headline, .subheadline, .largeTitle, .title1, .title2, .title3 ]
for style in textStyles {
    let nfont = UIFont(descriptor: .preferredFontDescriptor(withTextStyle: style), size: 0)
    let mfont = UIFont(descriptor: .preferredMonoFontDescriptor(withTextStyle: style), size: 0)
    print(style)
    print(nfont)
    print(mfont)
}

如果您比较每对结果，它们具有相同的大小、粗细和样式，只是字体不同。