時(shí)間函數(shù)：動(dòng)畫總會(huì)在設(shè)定的時(shí)間長度內(nèi)執(zhí)行完乞巧，在這段時(shí)間內(nèi)未荒，動(dòng)畫的變化速度有多快，主要決定于時(shí)間函數(shù)

CA_EXTERN NSString * const kCAMediaTimingFunctionLinear  //線性函數(shù)
    CA_AVAILABLE_STARTING (10.5, 2.0, 9.0, 2.0);
CA_EXTERN NSString * const kCAMediaTimingFunctionEaseIn  //緩入
    CA_AVAILABLE_STARTING (10.5, 2.0, 9.0, 2.0);
CA_EXTERN NSString * const kCAMediaTimingFunctionEaseOut  //緩出
    CA_AVAILABLE_STARTING (10.5, 2.0, 9.0, 2.0);
CA_EXTERN NSString * const kCAMediaTimingFunctionEaseInEaseOut  //慢入慢出
    CA_AVAILABLE_STARTING (10.5, 2.0, 9.0, 2.0);
CA_EXTERN NSString * const kCAMediaTimingFunctionDefault  //默認(rèn)
    CA_AVAILABLE_STARTING (10.6, 3.0, 9.0, 2.0);

• 線性函數(shù)

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• 緩入

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• 緩出

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• 慢入慢出

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• 默認(rèn)

Paste_Image.png

基本動(dòng)畫.gif

思路：拆分動(dòng)畫

• 1.把基礎(chǔ)圖形設(shè)置為兩個(gè)連著的半圓弧

Paste_Image.png

   CAShapeLayer * first = [CAShapeLayer layer];
    first.path = [self wormRunLongPath];
    first.lineWidth = 10;
    first.lineCap = kCALineCapRound;
    first.lineJoin = kCALineJoinRound;
    first.strokeColor = [UIColor redColor].CGColor;
    first.fillColor = [UIColor clearColor].CGColor;
    [self.layer addSublayer:first];

- (CGPathRef)wormRunLongPath {
    //中間點(diǎn)
    CGPoint center = CGPointMake(220, 300/2);
    CGFloat radius = 30;
    UIBezierPath *path = [UIBezierPath bezierPathWithArcCenter:CGPointMake(center.x  - radius , center.y) radius:radius startAngle:M_PI endAngle:2 * M_PI clockwise:YES];
   [path addArcWithCenter:CGPointMake(center.x  + radius, center.y) radius:radius startAngle:M_PI endAngle:2 * M_PI clockwise:YES];
    return path.CGPath;
}

運(yùn)行交煞，就得到了上面兩個(gè)半圓的效果咏窿。

• 2 那么接下來我們要實(shí)現(xiàn)讓它動(dòng)起來:實(shí)現(xiàn)紅色蟲運(yùn)動(dòng)的前半部分如下圖

基本動(dòng)畫分解1.gif

   //第一階段蟲子的拉伸
    CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"strokeEnd"];
    animation.fromValue = [NSNumber numberWithFloat:0.0];
    animation.toValue = [NSNumber numberWithFloat:0.5];
   //從0到0.5表示動(dòng)畫的過程從無到一個(gè)半圓
    animation.duration = 0.75;
    animation.timingFunction = [CAMediaTimingFunction functionWithControlPoints:0.42 :0.0 :1.0 :0.55];
    animation.removedOnCompletion = false;
    animation.fillMode = kCAFillModeForwards;

運(yùn)行，OK.

• 3 實(shí)現(xiàn)紅色蟲前半部收縮的效果如下圖

基本動(dòng)畫分解2.gif

    //第一階段蟲子的縮小
    CABasicAnimation *animation1 = [CABasicAnimation animationWithKeyPath:@"strokeStart"];
    animation1.fromValue = [NSNumber numberWithFloat:0.0];
    animation1.toValue = [NSNumber numberWithFloat:0.5];
    animation1.duration = 0.45;
    animation1.beginTime = 0.75;
    animation1.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
    animation1.fillMode = kCAFillModeForwards;

稍微注意一下我們就發(fā)現(xiàn)其實(shí)只是keyPath的區(qū)別错敢，一個(gè)是start,一個(gè)是end翰灾，同事我們?cè)O(shè)置beginTime表示的是在2的效果完成之后才開始3的效果，剛好銜接上去就湊成了一個(gè)完整的動(dòng)畫稚茅。然后把這兩個(gè)放到一個(gè)動(dòng)畫組里面試試效果.

• 4 實(shí)現(xiàn)前半部分動(dòng)畫完整銜接如下圖

基本動(dòng)畫分解3.gif

 CAAnimationGroup *group = [CAAnimationGroup animation];
    group.animations = [NSArray  arrayWithObjects:animation,animation1,nil];
    group.repeatCount = HUGE_VALF;
    group.duration = 0.75 * 2;
    [self.firstWormShapeLayer addAnimation:group forKey:@"one"];

• 5.同理實(shí)現(xiàn)紅色蟲后半部分的拉伸和收縮如下圖

基本動(dòng)畫分解4.gif

基本動(dòng)畫分解5.gif

//第二階段蟲子的拉伸
    CABasicAnimation *animation2 = [CABasicAnimation animationWithKeyPath:@"strokeEnd"];
    animation2.fromValue = [NSNumber numberWithFloat:0.5];
    animation2.toValue = [NSNumber numberWithFloat:1.0];
    animation2.duration = 0.75;
    animation2.beginTime = 1.2;
    animation2.timingFunction = [CAMediaTimingFunction functionWithControlPoints:0.42 :0.0 :1.0 :0.55];
    animation2.fillMode = kCAFillModeForwards;
    //第二階段蟲子的縮小
    CABasicAnimation *animation3 = [CABasicAnimation animationWithKeyPath:@"strokeStart"];
    animation3.fromValue = [NSNumber numberWithFloat:0.5];
    animation3.toValue = [NSNumber numberWithFloat:1];
    animation3.duration = 0.45;
    animation3.beginTime = 0.75 + 1.2;
    animation3.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
    animation3.fillMode = kCAFillModeForwards;

• 6 把上面四個(gè)動(dòng)畫一起放入動(dòng)畫組里面實(shí)現(xiàn)效果如下圖

  
  
  基本動(dòng)畫分解6.gif
• 7 然后分析一下我們發(fā)現(xiàn)跟效果圖就差了一個(gè)關(guān)于x的位移

    //實(shí)現(xiàn)持續(xù)移動(dòng)的效果:第一階段平移
    CABasicAnimation *xTranslationAm = [CABasicAnimation animationWithKeyPath:@"transform.translation.x"];
    xTranslationAm.toValue = [NSNumber numberWithFloat: (60 / -1.0)];
    xTranslationAm.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseOut];
    xTranslationAm.duration = 1.18;
    xTranslationAm.fillMode = kCAFillModeForwards;
    //實(shí)現(xiàn)持續(xù)移動(dòng)的效果:第二階段平移
    CABasicAnimation *xTranslationAm2 = [CABasicAnimation animationWithKeyPath:@"transform.translation.x"];
    xTranslationAm2.toValue = [NSNumber numberWithFloat: (60 / -1.0) * 2];
    xTranslationAm2.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseOut];
    xTranslationAm2.duration = 1.18;
    xTranslationAm2.beginTime = 1.20;
    xTranslationAm2.fillMode = kCAFillModeForwards;
  

把位移加入到動(dòng)畫組里面運(yùn)行就實(shí)現(xiàn)了紅色的效果

![基本動(dòng)畫分解7.gif](http://upload-images.jianshu.io/upload_images/1851080-6b2a75e429e3baf3.gif?imageMogr2/auto-orient/strip)

同理纸淮，可實(shí)現(xiàn)黃色和綠色的加入。