需求 - 18 - “点赞动画”

coding那个开源项目的“点赞”的动画效果非常赞，既然开源的我就直接转载在自己的博客里啦！

需要准备的：

1.facebook 的pop库：你可以多种方式来达到，推荐的是CocoaPods但是有些人不喜欢用pods，自用工程还好，当需要转给别人的工程pods真的是很难管理，各种版本不一

所以我这里喜欢用直接的pop代码导入：
https://github.com/facebook/pop   Github上的源码，这可是有一万多个赞，一千多个关注的明星源码啊

2.点击前后的两张图片

3.用Category来实现

需要注意的是，导入pop会报几个常出现的问题，百度和google很容易得到解决方式

1.Xcode6以后不允许 将integer类型置成nil类型，所以改成0即可

2.需要引入几个库，这个只要根据报错类型也很容易，其实就两个：一个是CFTimeInterval所属的CoreFoundation，

另外一个是runtime的一个宏NS_INLINE，只要导入Foundation这个基础库就可以啦

解决pop库的问题之后，代码就非常简单啦

#import "POPCustomAnimation.h"
#import "UIButton+PopAnimation.h"

@implementation UIButton (PopAnimation)

- (void)animateToImage:(NSString *)imageName
{
UIImage* image = [UIImage imageNamed:imageName];

if (!image)
{
return;
}

[self setImage:image forState:UIControlStateNormal];

if ([self superview])
{
UIView* superView = [self superview];
UIImageView* imageView = [[UIImageView alloc] initWithImage:image];
CGRect vFrame = [self convertRect:self.imageView.frame toView:superView];
imageView.frame = vFrame;
[superView addSubview:imageView];

//animation
CGAffineTransform fromTransform = imageView.transform;
CGPoint fromCenter = imageView.center;
CGFloat dx = CGRectGetWidth(self.frame) / 2;
CGFloat dy = CGRectGetHeight(self.frame) * 3;
CGFloat dScale = 3.0;
CGFloat dRotation = M_PI_4;

NSTimeInterval moveDuration = 1.0;

POPCustomAnimation* moveA = [POPCustomAnimation animationWithBlock:^BOOL(id target, POPCustomAnimation* animation){

float time_percent = (animation.currentTime - animation.beginTime) / moveDuration;

UIView* view = (UIView*)target;

//抛物线移动
CGPoint toCenter = CGPointMake(fromCenter.x + time_percent * dx, fromCenter.y - (dy * time_percent * (2 - time_percent)));

view.center = toCenter;

CGAffineTransform toTransform = fromTransform;
toTransform = CGAffineTransformTranslate(toTransform, 50, -50);

//线性放大
CGFloat toScale = 1 + time_percent * (dScale - 1);
toTransform = CGAffineTransformMakeScale(toScale, toScale);

//cos曲线旋转（先慢后快）
CGFloat toRotation = dRotation * (1 - cosf(time_percent * M_PI_2));

toTransform = CGAffineTransformRotate(toTransform, toRotation);
view.transform = toTransform;

view.alpha = 1 - time_percent;

return time_percent < 1.0;
}];

[imageView pop_addAnimation:moveA forKey:@"animateToImage"];
}
}

@end