iOS字体下载

iOS6之后的系统，苹果官方支持动态下载官方提供的中文字体。这样不仅可以避免版权问题，也可以减少项目的体积。下面就简单的介绍字体库的动态下载。

获取字体的PostScript###

MAC系统自带的字体集中，具体位置如下图。

字体PostScript位置

1、判断字体是否已存在###

示例代码如下：

+ (BOOL)isFontDownloaded:(NSString *)postScriptName{
   UIFont *font = [UIFont fontWithName:postScriptName size:12.0]; 
   if (font && ([font.fontName compare:postScriptName] == NSOrderedSame || [font.familyName compare:postScriptName] == NSOrderedSame)) { 
      return YES; 
   } 
   return NO;
}

2、开始下载字体###

示例代码如下：

+ (void)downloadFontWithPostScriptName:(NSString *)postScriptName{
    if ([self isFontDownloaded:postScriptName]) {
        return;
    }
    NSMutableDictionary *attrsDictionary = [NSMutableDictionary dictionaryWithObjectsAndKeys:postScriptName,kCTFontNameAttribute, nil];
    CTFontDescriptorRef descriptor = CTFontDescriptorCreateWithAttributes((__bridge CFDictionaryRef)attrsDictionary);
    NSMutableArray *descriptorArray = [NSMutableArray array];
    [descriptorArray addObject:(__bridge id)descriptor];
    CFRelease(descriptor);
    
    __block BOOL errorDuringDownload = NO;
    CTFontDescriptorMatchFontDescriptorsWithProgressHandler((__bridge CFArrayRef)descriptorArray, NULL, ^bool(CTFontDescriptorMatchingState state, CFDictionaryRef  _Nonnull progressParameter) {
        double progressValue = [[(__bridge NSDictionary *)progressParameter objectForKey:(id)kCTFontDescriptorMatchingPercentage] doubleValue];
        if (state == kCTFontDescriptorMatchingDidBegin) {
            NSLog(@"字体已经匹配");
        }else if (state == kCTFontDescriptorMatchingDidFinish){
            if (!errorDuringDownload) {
                NSLog(@"字体%@下载完成",postScriptName);
            }
        }else if (state == kCTFontDescriptorMatchingWillBeginDownloading){
            NSLog(@"字体开始下载");
        }else if (state == kCTFontDescriptorMatchingDidFinishDownloading){
            NSLog(@"字体下载完成");
            dispatch_async(dispatch_get_main_queue(), ^{
                // 在此修改UI控件的字体
            });
        }else if (state == kCTFontDescriptorMatchingDownloading){
            NSLog(@"下载进度%.0f%%",progressValue);
        }else if (state == kCTFontDescriptorMatchingDidFailWithError){
            NSError *error = [(__bridge NSDictionary *)progressParameter objectForKey:(id)kCTFontDescriptorMatchingError];
            NSString *errorMesage = [NSString string];
            if (error != nil) {
                errorMesage = [error description];
            } else {
                errorMesage = @"ERROR MESSAGE IS NOT AVAILABLE!";
            }
            // 设置下载失败标志
            errorDuringDownload = YES;
            NSLog(@"下载错误：%@",errorMesage);
        }
        return (bool)YES;
    });
    
}