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"];  
    }