- (void)drawRect:(CGRect)rect {
 // Drawing code
 // 初始化UIBezierPath
 UIBezierPath *path = [UIBezierPath bezierPath];
 // 首先设置一个起始点
 CGPoint startPoint = CGPointMake(rect.size.width/2, 120);
 // 以起始点为路径的起点
 [path moveToPoint:startPoint];
 // 设置一个终点
 CGPoint endPoint = CGPointMake(rect.size.width/2, rect.size.height-40);
 // 设置第一个控制点
 CGPoint controlPoint1 = CGPointMake(100, 20);
 // 设置第二个控制点
 CGPoint controlPoint2 = CGPointMake(0, 180);
 // 添加三次贝塞尔曲线
 [path addCurveToPoint:endPoint controlPoint1:controlPoint1 controlPoint2:controlPoint2];
 // 设置另一个起始点
 [path moveToPoint:endPoint];
 // 设置第三个控制点
 CGPoint controlPoint3 = CGPointMake(rect.size.width-100, 20);
 // 设置第四个控制点
 CGPoint controlPoint4 = CGPointMake(rect.size.width, 180);
 // 添加三次贝塞尔曲线
 [path addCurveToPoint:startPoint controlPoint1:controlPoint4 controlPoint2:controlPoint3];
 // 设置线宽
 path.lineWidth = 3;
 // 设置线断面类型
 path.lineCapStyle = kCGLineCapRound;
 // 设置连接类型
 path.lineJoinStyle = kCGLineJoinRound;
 // 设置画笔颜色
 [[UIColor redColor] set];
 [path stroke];
}

 HeartView *heart = [[HeartView alloc] init];
 heart.frame = CGRectMake(0, 0, Screen_Width, Screen_Height-Screen_Height);
 [self.view addSubview:heart];

 CAKeyframeAnimation *animation = [CAKeyframeAnimation animationWithKeyPath:@"position"];
 // 设置动画的路径为心形路径
 animation.path = self.path.CGPath;
 // 动画时间间隔
 animation.duration = 3.0f;
 // 重复次数为最大值
 animation.repeatCount = FLT_MAX;
 animation.removedOnCompletion = NO;
 animation.fillMode = kCAFillModeForwards;
 // 将动画添加到动画视图上
 [_demoView.layer addAnimation:animation forKey:nil];