实现对字符串的画线动画

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//
//  ZYAnimationLayer.m
//  ZYDrawString
//
//  Created by soufun on 15-1-9.
//  Copyright (c) 2015年 ZY. All rights reserved.
//

#import "ZYAnimationLayer.h"

@interface ZYAnimationLayer()
@property (nonatomic, retain) CAShapeLayer *pathLayer;
@property (nonatomic, retain) CALayer *penLayer;
@end

@implementation ZYAnimationLayer
+(void)createAnimationLayerWithString:(NSString*)string andRect:(CGRect)rect andView:(UIView *)view andFont:(UIFont*)ui_font andStrokeColor:(UIColor*)color
{
    ZYAnimationLayer * animationLayer = [ZYAnimationLayer 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 = animationLayer.bounds;
    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;
    
    UIImage *penImage = [UIImage imageNamed:@"noun_project_347_2.png"];
    CALayer *penLayer = [CALayer layer];
    penLayer.contents = (id)penImage.CGImage;
    penLayer.anchorPoint = CGPointZero;
    penLayer.frame = CGRectMake(0.0f, 0.0f, penImage.size.width, penImage.size.height);
    [pathLayer addSublayer:penLayer];
    animationLayer.penLayer = penLayer;
    
    [animationLayer.pathLayer removeAllAnimations];
    [animationLayer.penLayer removeAllAnimations];
    
    animationLayer.penLayer.hidden = NO;
    
    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
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摘自：
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<a target=_blank href="https://github.com/bjzhangyang/ZYDrawString" target="_blank" id="url_1" style="font-stretch: normal; font-family: 宋体, 'Lucida Grande', Geneva, Arial, Verdana, Tahoma, Arial, 微软雅黑, 黑体; text-decoration: none; color: rgb(34, 153, 234);">https://github.com/bjzhangyang/ZYDrawString</a>