iOS-如何为自定义字体设置后备字体？

Question

I'm using a bold custom font for my app's navigation bar titles.

I've also just localised my app. For languages the font doesn't support (primarily Asian languages), iOS falls back to the system default - alas, this is not a bold system default but a standard weighting not suitable for headings.

What can I do to change this?

Answer 1

Answer to the bounty question

Here is an extension allowing to construct NSAttributedString with a second set of attributes that will be applied to latin characters:

extension String {
    private var englishRanges: [NSRange] {
        let set = NSMutableCharacterSet(range: NSRange(location: 0x0041, length: 26))
        set.addCharactersInRange(NSRange(location: 0x0061, length: 26))
        var start = startIndex
        var englishRanges = [Range<String.Index>]()
        while let range = rangeOfCharacterFromSet(set, options: [], range: start..<endIndex) {
            start = range.endIndex
            englishRanges.append(range)
        }
        return englishRanges.map {NSRange(location: startIndex.distanceTo($0.startIndex), length: $0.count)}
    }

    func attributedMultilanguageString(options: [String:AnyObject], englishOptions:[String:AnyObject]) -> NSAttributedString {
        let string = NSMutableAttributedString(string: self, attributes: options)
        englishRanges.forEach {
            string.setAttributes(englishOptions, range: $0)
        }
        return string
    }
}

Example usage:

let font = UIFont(name: "Arial-BoldMT", size: 18.0)!
let englishFont = UIFont(name: "Chalkduster", size: 18.0)!
let label = UILabel()
label.attributedText = "some string 111".attributedMultilanguageString([ NSFontAttributeName: font], englishOptions: [ NSFontAttributeName: englishFont])

Second approach

And this extension allows you to specify fallback font instead of using a second font for specific characters:

extension String {
    private func unsupportedCharacterIndexes(font: String) -> [String.Index] {
        let font = CGFontCreateWithFontName(font)
        return characters.indices.filter {CGFontGetGlyphWithGlyphName(font, String(self[$0])) == 0}
    }

    func attributedString(fontName: String, fallbackFontName: String, fontSize: CGFloat, options: [String:AnyObject]? = nil) -> NSAttributedString {
        var options = options ?? [String:AnyObject]()
        options[NSFontAttributeName] = UIFont(name: fontName, size: fontSize)
        let string = NSMutableAttributedString(string: self, attributes: options)
        options[NSFontAttributeName] = UIFont(name: fallbackFontName, size: fontSize)
        unsupportedCharacterIndexes(fontName).forEach {
            string.setAttributes(options, range: NSRange(location: startIndex.distanceTo($0), length: 1))
        }
        return string
    }
}

Example usage:

let label = UILabel()
label.attributedText = "some текст".attributedString("Chalkduster", fallbackFontName: "Baskerville-SemiBoldItalic", fontSize: 18)

Answer 2

+ (UIFont *)addFallbacktoFont:(UIFont*)font{
   UIFontDescriptor* originalDescriptor = [font fontDescriptor];

   UIFontDescriptor* fallbackDescriptor = [originalDescriptor fontDescriptorByAddingAttributes:@{UIFontDescriptorNameAttribute:@"Helvetica Neue"}];

   UIFontDescriptor* repaired = [originalDescriptor fontDescriptorByAddingAttributes:@{UIFontDescriptorCascadeListAttribute:@[
                                                                                            fallbackDescriptor
                                                                                            ]}];

   font = [UIFont fontWithDescriptor:repaired size:0.0];

   return font;
}  

Change "Helvetica Neue" to any fontName you want to fall back,and you will get a fallback Font.

Answer 3

I'm not sure if it's the best way but I use the following snippet to check for specific languages:

//store all fallback languages in this array (eg.: el = greek, ru = russian)
NSArray *fallbackFont = @[@"el", @"ru"];
NSString *lang = [[NSLocale preferredLanguages] objectAtIndex:0]
BOOL hasFallbackFont = [fallbackFont containsObject:lang];

NSString *fontNameBold = hasFallbackFont ? @"Fallback-Font-Bold" : @"Regular-Font-Bold";

...

myLabel.font = [UIFont fontWithName:fontNameBold size:12.0];

Answer 4

The basic is of course a regular if to replace the custom font if the language is not supported. The challenge is in other words to find out whether the language in question is supported or not.

Not the sexiest of solutions, but I believe it should work:

• Convert your font to a CGFontRef. CGFontRef cgFontVersion = CGFontCreateWithFontName((CFStringRef)uiFont.fontName);
• use CGFontGetGlyphWithGlyphName towards an array containing the necessary glyphs from each language you plan to support.*
• If CGFontGetGlyphWithGlyphName returns 0 your custom font is NOT supported and you can use whatever fall-back-font you would like.

*getting hold of these might be the hardest part, the nice part as that you'd only need to do this once and could use it again for future projects...

A more pragmatic solution would be to do something like Hannes suggests, but then you would need to redo it for each language manually for every new custom font you decide to use in the future.

Answer 5

Please ensure you have the desired font you want to display as default font, not the system default. But, something similar to the desired font, a default.

// Method that returns the font for buttons and title bar
// Pass in your custom font as a string argument/ parameter
func getFont(fontName: String, size fontSize: CGFloat)-> UIFont {

// Unwrap your custom font here, if font exists "Hooray!" else "Bo-Oh!" return a default one
if let customFont = UIFont(named: fontName, size: fontSize ) {
  return customFont
} else {
// This gets the system default font and returns to you!
  return UIFont(named: defaultFont, size: fontSize )
}

This ensure we always have a font to use. Now, you can take the rest from here on how to set the font and its style to the preferred view/controls.

That should do it. Do tell us about how it goes for you!