在Swift 3 / iOS10中使用Dynamic Type和自定义字体的更好方法

The problem with this method is that the text size won’t change until the user goes back to the app,and then the user would see the old text size change to the new size,which is not ideal.

我分享你的想法,这可能是一个更好的用户体验,但我想你有点过分思考它.

如果您查看系统提供的应用程序(例如联系人),您将清楚地看到在用户返回应用程序之前不会进行刷新.

顺便说一下,你可以为Swift 3重构一下你的代码：

extension UIFontDescriptor {

    private struct SubStruct {
        static var preferredFontName: String = "Avenir-medium"
    }

    static let fontSizeTable: [UIFontTextStyle: [UIContentSizeCategory: CGFloat]] = [
        .headline: [
            .accessibilityExtraExtraExtraLarge: 23,.accessibilityExtraExtraLarge: 23,.accessibilityExtraLarge: 23,.accessibilityLarge: 23,.accessibilityMedium: 23,.extraExtraExtraLarge: 23,.extraExtraLarge: 21,.extraLarge: 19,.large: 17,.medium: 16,.small: 15,.extraSmall: 14
        ],.subheadline: [
            .accessibilityExtraExtraExtraLarge: 21,.accessibilityExtraExtraLarge: 21,.accessibilityExtraLarge: 21,.accessibilityLarge: 21,.accessibilityMedium: 21,.extraExtraExtraLarge: 21,.extraExtraLarge: 19,.extraLarge: 17,.large: 15,.medium: 14,.small: 13,.extraSmall: 12
        ],.body: [
            .accessibilityExtraExtraExtraLarge: 53,.accessibilityExtraExtraLarge: 47,.accessibilityExtraLarge: 40,.accessibilityLarge: 33,.accessibilityMedium: 28,.caption1: [
            .accessibilityExtraExtraExtraLarge: 18,.accessibilityExtraExtraLarge: 18,.accessibilityExtraLarge: 18,.accessibilityLarge: 18,.accessibilityMedium: 18,.extraExtraExtraLarge: 18,.extraExtraLarge: 16,.extraLarge: 14,.large: 12,.medium: 11,.small: 11,.extraSmall: 11
        ],.caption2: [
            .accessibilityExtraExtraExtraLarge: 17,.accessibilityExtraExtraLarge: 17,.accessibilityExtraLarge: 17,.accessibilityLarge: 17,.accessibilityMedium: 17,.extraExtraExtraLarge: 17,.extraExtraLarge: 15,.extraLarge: 13,.large: 11,.footnote: [
            .accessibilityExtraExtraExtraLarge: 19,.accessibilityExtraExtraLarge: 19,.accessibilityExtraLarge: 19,.accessibilityLarge: 19,.accessibilityMedium: 19,.extraExtraExtraLarge: 19,.extraExtraLarge: 17,.extraLarge: 15,.large: 13,.medium: 12,.small: 12,.extraSmall: 12
        ]
    ]

    final class func preferredDescriptor(textStyle: UIFontTextStyle) -> UIFontDescriptor {
        let contentSize = UIApplication.shared.preferredContentSizeCategory
        let style = fontSizeTable[textStyle]!
        return UIFontDescriptor(name: SubStruct.preferredFontName,size: style[contentSize]!)
    }
}

无需转换为NSDictionary或NSNumber并间接获取floatValue.

这样,您的呼叫站点可以使用以下更易读的代码：

func userChangedTextSize(notification: NSNotification) {
    label.font = UIFont(descriptor: .preferredDescriptor(textStyle: .body),size: 0)

}

编辑：当我正在进行同样的工作时,我将上述(在常见的解决方案中)改进为更容易的方式.

import UIKIt

extension UIFont {

    private struct CustomFont {
        static var fontFamily = "Avenir"
    }

    /// Returns a bold version of `self`
    public var bolded: UIFont {
        return fontDescriptor.withSymbolicTraits(.traitBold)
            .map { UIFont(descriptor: $0,size: 0) } ?? self
    }

    /// Returns an italic version of `self`
    public var italicized: UIFont {
        return fontDescriptor.withSymbolicTraits(.traitItalic)
            .map { UIFont(descriptor: $0,size: 0) } ?? self
    }

    /// Returns a scaled version of `self`
    func scaled(scaleFactor: CGFloat) -> UIFont {
        let newDescriptor = fontDescriptor.withSize(fontDescriptor.pointSize * scaleFactor)
        return UIFont(descriptor: newDescriptor,size: 0)
    }

    class func preferredCustomFont(forTextStyle textStyle: UIFontTextStyle) -> UIFont {
        // we are using the UIFontDescriptor which is less expensive than creating an intermediate UIFont
        let systemFontDescriptor = UIFontDescriptor.preferredFontDescriptor(withTextStyle: textStyle)

        let customFontDescriptor = UIFontDescriptor.init(fontAttributes: [
            UIFontDescriptorFamilyAttribute: CustomFont.fontFamily,UIFontDescriptorSizeAttribute: systemFontDescriptor.pointSize // use the font size of the default dynamic font
        ])

        // return font of new family with same size as the preferred system font
        return UIFont(descriptor: customFontDescriptor,size: 0)
    }

}

用法

func userChangedTextSize(notification: NSNotification) {
    label.font = UIFont.preferredCustomFont(forTextStyle: .headline)
    // or in Bold / Italic:
    // label.font = UIFont.preferredCustomFont(forTextStyle: .headline).bolded
    // label.font = UIFont.preferredCustomFont(forTextStyle: .headline).italicized
}