iOS 字體下載

iOS能夠動態的爲系統下載字體，這些字體都下載到了系統的目錄下，而且能夠被其餘應用公用

來看下如何實現動態下載：

 // 建立下載字體請求描述的準備
    NSMutableDictionary *attrs = [NSMutableDictionary dictionaryWithObjectsAndKeys:fontName, kCTFontNameAttribute, nil];
    CTFontDescriptorRef desc = CTFontDescriptorCreateWithAttributes((__bridge CFDictionaryRef)attrs);
    NSMutableArray *descs = [NSMutableArray arrayWithCapacity:0];
    [descs addObject:(__bridge id)desc];
    CFRelease(desc);

    
    //開始下載字體
    __block BOOL errorDuringDownload = NO;
    CTFontDescriptorMatchFontDescriptorsWithProgressHandler( (__bridge CFArrayRef)descs, NULL,  ^(CTFontDescriptorMatchingState state, CFDictionaryRef progressParameter) {
        
        //NSLog( @"state %d - %@", state, progressParameter);
        
        double progressValue = [[(__bridge NSDictionary *)progressParameter objectForKey:(id)kCTFontDescriptorMatchingPercentage] doubleValue];
        
        if (state == kCTFontDescriptorMatchingDidBegin) {
            dispatch_async( dispatch_get_main_queue(), ^ {
                // Show an activity indicator
                [_fActivityIndicatorView startAnimating];
                _fActivityIndicatorView.hidden = NO;
                
                // Show something in the text view to indicate that we are downloading
                _fTextView.text= [NSString stringWithFormat:@"Downloading %@", fontName];
                _fTextView.font = [UIFont systemFontOfSize:14.];
                
                NSLog(@"開始匹配...");
            });
        } else if (state == kCTFontDescriptorMatchingDidFinish) {
            dispatch_async( dispatch_get_main_queue(), ^ {
                // Remove the activity indicator
                [_fActivityIndicatorView stopAnimating];
                _fActivityIndicatorView.hidden = YES;
                
                // Display the sample text for the newly downloaded font
                NSUInteger sampleIndex = [_fontNames indexOfObject:fontName];
                _fTextView.text = [_fontSamples objectAtIndex:sampleIndex];
                _fTextView.font = [UIFont fontWithName:fontName size:24.];
                
                // Log the font URL in the console
                CTFontRef fontRef = CTFontCreateWithName((__bridge CFStringRef)fontName, 0., NULL);
                CFStringRef fontURL = CTFontCopyAttribute(fontRef, kCTFontURLAttribute);
                NSLog(@"%@", (__bridge NSURL*)(fontURL));
                CFRelease(fontURL);
                CFRelease(fontRef);
                
                if (!errorDuringDownload) {
                    NSLog(@"%@ downloaded", fontName);
                }
            });
        } else if (state == kCTFontDescriptorMatchingWillBeginDownloading) {
            dispatch_async( dispatch_get_main_queue(), ^ {
                // Show a progress bar
                _fProgressView.progress = 0.0;
                _fProgressView.hidden = NO;
                NSLog(@"開始下載...");
            });
        } else if (state == kCTFontDescriptorMatchingDidFinishDownloading) {
            dispatch_async( dispatch_get_main_queue(), ^ {
                // Remove the progress bar
                _fProgressView.hidden = YES;
                NSLog(@"下載完成");
            });
        } else if (state == kCTFontDescriptorMatchingDownloading) {
            dispatch_async( dispatch_get_main_queue(), ^ {
                // Use the progress bar to indicate the progress of the downloading
                [_fProgressView setProgress:progressValue / 100.0 animated:YES];
                NSLog(@"下載進度 %.0f%% complete", progressValue);
            });
        } else if (state == kCTFontDescriptorMatchingDidFailWithError) {
            // An error has occurred.
            // Get the error message
            NSError *error = [(__bridge NSDictionary *)progressParameter objectForKey:(id)kCTFontDescriptorMatchingError];
            if (error != nil) {
                _errorMessage = [error description];
            } else {
                _errorMessage = @"ERROR MESSAGE IS NOT AVAILABLE!";
            }
            // Set our flag
            errorDuringDownload = YES;
            
            dispatch_async( dispatch_get_main_queue(), ^ {
                _fProgressView.hidden = YES;
                NSLog(@"下載失敗: %@", _errorMessage);
            });
        }
        
        return (bool)YES;
    });

 

  NSString *ffontName = @"STBaoli-SC-Regular";
    UIFont* aFont = [UIFont fontWithName:fontName size:12.];
    
    // 判斷字體是否已經下載
    if (aFont && ([aFont.fontName compare:fontName] == NSOrderedSame || [aFont.familyName compare:fontName] == NSOrderedSame)) {
        // 使用已下載的字體
        NSUInteger sampleIndex = [_fontNames indexOfObject:fontName];
        _fTextView.text = [_fontSamples objectAtIndex:sampleIndex];
        _fTextView.font = [UIFont fontWithName:fontName size:24.];
        return;
    }