1. 效果圖

   
   
   水波紋.gif
2. 實現(xiàn)代碼

CALayer * spreadLayer;
    spreadLayer = [CALayer layer];
    CGFloat diameter = 160;  //擴散的大小
    spreadLayer.bounds = CGRectMake(0,0, diameter, diameter);
    spreadLayer.cornerRadius = diameter/2; //設置圓角變?yōu)閳A形
    spreadLayer.position = self.scanCodeBtn.center;
    spreadLayer.backgroundColor = COLOR_GREEN.CGColor;
    // 把擴散層放到按鈕下面
    [self.layer insertSublayer:spreadLayer below:self.scanCodeBtn.layer];

  CAMediaTimingFunction * defaultCurve = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionDefault];
  CAAnimationGroup * animationGroup = [CAAnimationGroup animation];
  animationGroup.duration = 2.5;//1.75
  animationGroup.repeatCount = INFINITY;//重復無限次
  animationGroup.removedOnCompletion = NO;
  animationGroup.timingFunction = defaultCurve;
  
  //尺寸比例動畫
  CABasicAnimation *scaleAnimation = [CABasicAnimation animationWithKeyPath:@"transform.scale.xy"];
  scaleAnimation.fromValue = @0.5;//開始的大小
  scaleAnimation.toValue = @1.0;//最后的大小
  scaleAnimation.duration = 1.5;//動畫持續(xù)時間
  
  //透明度動畫
  CAKeyframeAnimation *opacityAnimation = [CAKeyframeAnimation animationWithKeyPath:@"opacity"];
  opacityAnimation.duration = 2.5;
  opacityAnimation.values = @[@1, @0.5,@0];//透明度值的設置
  //    opacityAnimation.values = @[@1, @0.67,@0.33];//透明度值的設置
  opacityAnimation.keyTimes = @[@0, @0.5,@1.0];//關鍵幀
  //    opacityAnimation.keyTimes = @[@0, @0.33,@0.67];//關鍵幀
  opacityAnimation.removedOnCompletion = NO;
  
  animationGroup.animations = @[scaleAnimation, opacityAnimation];//添加到動畫組
  [spreadLayer addAnimation:animationGroup forKey:@"pulse"];

3. Demo地址