文字渐渐显示效果

#import "DMAnimationLayer.h"@interface DMAnimationLayer()@property (nonatomic, retain) CAShapeLayer *pathLayer;@property (nonatomic, retain) CALayer *penLayer;@end@implementation DMAnimationLayer+(void)createAnimationLayerWithString:(NSString*)string andRect:(CGRect)rect andView:(UIView *)view andFont:(UIFont*)ui_font andStrokeColor:(UIColor*)color{    DMAnimationLayer * animationLayer = [DMAnimationLayer layer];    animationLayer.frame = rect;    [view.layer addSublayer:animationLayer];        if (animationLayer.pathLayer != nil) {        [animationLayer.penLayer removeFromSuperlayer];        [animationLayer.pathLayer removeFromSuperlayer];        animationLayer.pathLayer = nil;        animationLayer.penLayer = nil;    }    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 each RUN    for (CFIndex runIndex = 0; runIndex < CFArrayGetCount(runArray); runIndex++)    {        // Get FONT for this run        CTRunRef run = (CTRunRef)CFArrayGetValueAtIndex(runArray, runIndex);        CTFontRef runFont = CFDictionaryGetValue(CTRunGetAttributes(run), kCTFontAttributeName);                // for each GLYPH in run        for (CFIndex runGlyphIndex = 0; runGlyphIndex < CTRunGetGlyphCount(run); runGlyphIndex++)        {            CFRange thisGlyphRange = CFRangeMake(runGlyphIndex, 1);            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);            }        }    }    CFRelease(line);        UIBezierPath *path = [UIBezierPath bezierPath];    [path moveToPoint:CGPointZero];    [path appendPath:[UIBezierPath bezierPathWithCGPath:letters]];        CGPathRelease(letters);    CFRelease(font);//    CAShapeLayer *pathLayer = [CAShapeLayer layer];    pathLayer.frame = CGRectMake(0, 0, rect.size.width, rect.size.height -230);    pathLayer.bounds = CGPathGetBoundingBox(path.CGPath);    pathLayer.geometryFlipped = YES;    pathLayer.path = path.CGPath;    pathLayer.strokeColor = [color CGColor];    pathLayer.fillColor = nil;    pathLayer.lineWidth = 1.0f;    pathLayer.lineJoin = kCALineJoinBevel;    [animationLayer addSublayer:pathLayer];    animationLayer.pathLayer = pathLayer;          CABasicAnimation *pathAnimation = [CABasicAnimation animationWithKeyPath:@"strokeEnd"];    pathAnimation.duration = 5.0;    pathAnimation.fromValue = [NSNumber numberWithFloat:0.0f];    pathAnimation.toValue = [NSNumber numberWithFloat:1.0f];    [animationLayer.pathLayer addAnimation:pathAnimation forKey:@"strokeEnd"];        CAKeyframeAnimation *penAnimation = [CAKeyframeAnimation animationWithKeyPath:@"position"];    penAnimation.duration = 5.0;    penAnimation.path = animationLayer.pathLayer.path;    penAnimation.calculationMode = kCAAnimationPaced;    penAnimation.delegate = animationLayer;    [animationLayer.penLayer addAnimation:penAnimation forKey:@"position"];}- (void) animationDidStop:(CAAnimation *)anim finished:(BOOL)flag{    self.penLayer.hidden = YES;}@end

第三方：https://github.com/overboming/ZCAnimatedLabel