Pop框架简述

Facebook发布了Paper之后，进一步开源了其背后的动画引擎Pop，此框架并不满足于苹果自身的动画单调性，致力于给用户一种逼真的动画效果，可以减少用户对于苹果原生Core Animation 复杂的运算，并且Pop提供的API和苹果原生的API用法类似，让开发者更容易接受。使用pop框架进行动画展示会让你的App看起来更加有生气，感觉像是活了一样。

它主要包含的动画：

　　POPSpringAnimation 有弹性效果的动画类

      POPBasicAnimation基本动画

      POPDecayAnimation衰减动画类

      POPCustomAnimation可以自定义动画的类

个人使用第一种动画比较多，做了个小Demo，仅做参考。

@interface ViewController ()

@property (nonatomic,strong) UIButton *button;
    
    @property (nonatomic,assign) BOOL isSelected;
    
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    [self.view addSubview:self.button ];
    [self.button addTarget:self action:@selector(buttonClick) forControlEvents:UIControlEventTouchUpInside];
    [self.button setBackgroundImage:[UIImage imageNamed:@"deleteButtonNormal"] forState:UIControlStateNormal];
    self.button.backgroundColor = [UIColor orangeColor];
    
    self.isSelected = YES;
}

//懒加载
- (UIButton *)button{
    if (_button == nil) {
        _button  = [[UIButton alloc]initWithFrame:CGRectMake(50, 70, 26, 26)];
    }
    return  _button;
}
    
- (void)buttonClick{
    POPSpringAnimation *springAnimation = [POPSpringAnimation animationWithPropertyNamed:kPOPLayerSize];
    
    if (self.isSelected == YES) {
        [_button setBackgroundImage:[UIImage imageNamed:@"deleteButtonSelected"] forState:UIControlStateNormal];
        self.isSelected = NO;
        springAnimation.toValue = [NSValue valueWithCGSize:CGSizeMake(28, 28)];
    }else{
        [_button setBackgroundImage:[UIImage imageNamed:@"deleteButtonNormal"] forState:UIControlStateNormal];
        self.isSelected = YES;
        springAnimation.toValue  = [NSValue valueWithCGSize:CGSizeMake(26, 26)];
    }
    //弹性值
    springAnimation.springBounciness = 30;
    //弹性速度
    springAnimation.springSpeed = 20;
    
    [self.button.layer pop_addAnimation:springAnimation forKey:@"changesize"];
}

这是一个很简单的展示，作为学习pop框架的开始。