iOS--点赞动画效果

    int i = 0;
    [self.button setImage:[UIImage imageNamed:(i%2==0?@"2":@"1")] forState:UIControlStateNormal];
    CAKeyframeAnimation *k = [CAKeyframeAnimation animationWithKeyPath:@"transform.scale"];
    k.values = @[@(0.1),@(1.0),@(1.5)];
    k.keyTimes = @[@(0.0),@(0.5),@(0.8),@(1.0)];
    k.calculationMode = kCAAnimationLinear;
    i++;
    [self.button.layer addAnimation:k forKey:@"SHOW"];