title: A problem when try to zoom in & out of UIButton with CAAnimationGroup
body: <p>no have animation , cause i do it incorrect ?</p>
  
  <pre><code>-(void)swipeanimateDidStop {
  
      for (UIView *subview in self.swipingCell.backView.subviews){
          NSLog(@"%@",subview);
          // subview is UIButton
          [subview.layer addAnimation:[self ZoomAnimation] forKey:@"Zoom"];
  
      }
  }
  
  -(CAAnimationGroup *)ZoomAnimation {
      CAAnimationGroup *ZoomAnimation = [CAAnimationGroup animation];
      CABasicAnimation *In = [self zoomIn];
  
      ZoomAnimation.animations = [NSArray arrayWithObjects: In, nil];
      ZoomAnimation.duration = 2.0f;
      return ZoomAnimation;
  }
  
  -(CABasicAnimation *)zoomIn {
      CABasicAnimation *ZoomInAnimation = [CABasicAnimation animationWithKeyPath:@"transform"];
      ZoomInAnimation.beginTime = 0.0f;
      ZoomInAnimation.fromValue = [NSNumber numberWithFloat:20.0];
      ZoomInAnimation.toValue = [NSNumber numberWithFloat:1.0];
      ZoomInAnimation.duration = 2.0f;
      return ZoomInAnimation;
  }
  </code></pre>