心跳动画

    - (void)viewDidLoad {
        [super viewDidLoad];
        UIButton *heart = [[UIButton alloc]initWithFrame:CGRectMake(self.view.frame.size.width * 0.5 - 25, 200, 50, 50)];
        [self.view addSubview:heart];
        [heart setImage:[UIImage imageNamed:@"5_heart"] forState:UIControlStateNormal];
        [heart setImage:[UIImage imageNamed:@"5_heart_clicked"] forState:UIControlStateSelected];
        [heart addTarget:self action:@selector(heartButtonClick:) forControlEvents:UIControlEventTouchUpInside];
    }  

    /**
     *  心跳
     */
    - (void)heartButtonClick:(UIButton *)button{
        button.selected = !button.selected;
        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;
        [button.layer addAnimation:k forKey:@"SHOW"];
    }