iOS之String动态书写

/**
 String动画书写出来

 @param string 要写的字
 @param view 父视图
 @param ui_font 字体大小
 @param color 字体颜色
 */
- (void)createAnimationLayerWithString:(NSString*)string andView:(UIView *)view andFont:(UIFont*)ui_font andStrokeColor:(UIColor*)color{
    CTFontRef font =CTFontCreateWithName((CFStringRef)ui_font.fontName,
                                         ui_font.pointSize,
                                         NULL);
    CGMutablePathRef letters = CGPathCreateMutable();

    //这里设置画线的字体和大小
    NSDictionary *attrs = [NSDictionary dictionaryWithObjectsAndKeys:
                           (__bridge id)font, kCTFontAttributeName,
                           nil];
    NSAttributedString *attrString = [[NSAttributedString alloc] initWithString:string
                                                                     attributes:attrs];
    CTLineRef line = CTLineCreateWithAttributedString((CFAttributedStringRef)attrString);
    CFArrayRef runArray = CTLineGetGlyphRuns(line);

    for (CFIndex runIndex = ; runIndex < CFArrayGetCount(runArray); runIndex++)
    {
        CTRunRef run = (CTRunRef)CFArrayGetValueAtIndex(runArray, runIndex);
        CTFontRef runFont = CFDictionaryGetValue(CTRunGetAttributes(run), kCTFontAttributeName);

        for (CFIndex runGlyphIndex = ; runGlyphIndex < CTRunGetGlyphCount(run); runGlyphIndex++)
        {
            CFRange thisGlyphRange = CFRangeMake(runGlyphIndex, );
            CGGlyph glyph;
            CGPoint position;
            CTRunGetGlyphs(run, thisGlyphRange, &glyph);
            CTRunGetPositions(run, thisGlyphRange, &position);

            CGPathRef letter = CTFontCreatePathForGlyph(runFont, glyph, NULL);
            CGAffineTransform t = CGAffineTransformMakeTranslation(position.x, position.y);
            CGPathAddPath(letters, &t, letter);
            CGPathRelease(letter);
        }
    }

    CAShapeLayer *pathLayer = [CAShapeLayer layer];
    pathLayer.frame = CGRectMake(, , view.frame.size.width, view.frame.size.height );
    pathLayer.bounds = CGPathGetBoundingBox(letters);
    pathLayer.geometryFlipped = YES;
    pathLayer.path = letters;
    pathLayer.strokeColor = [color CGColor];
    pathLayer.fillColor = nil;
    pathLayer.lineWidth = 1.0f;
    pathLayer.lineJoin = kCALineJoinBevel;
    [view.layer addSublayer:pathLayer];

    CABasicAnimation *pathAnimation = [CABasicAnimation animationWithKeyPath:@"strokeEnd"];
    pathAnimation.duration = 5.0;
    pathAnimation.fromValue = [NSNumber numberWithFloat:0.0f];
    pathAnimation.toValue = [NSNumber numberWithFloat:1.0f];
    [pathLayer addAnimation:pathAnimation forKey:@"strokeEnd"];

    CGPathRelease(letters);
    CFRelease(font);
    CFRelease(line);
}

效果图