POP - 简单使用

POP是Facebook开源的一个动画库，该动画库基于CADisplayLink(Mac平台上使用的CVDisplayLink))实现的独立于Core Animation之外的动画库。以每秒60帧的速度渲染动画，所以看起来会非常流畅。

创建一个POP动画需要六步，下面我们来逐一介绍：

1.选择一个动画方式：

POP提供4种动画效果，POPBasicAnimation、POPSpringAnimation、POPDecayAnimation、POPCustomAnimation。这些动画效果可以基于CALayer、CAShapeLayer、NSLayoutConstraint、UIView、UIScrollView、UITableView、UINavigationBar、UITabBar等类。

POPBasicAnimation是一种基础动画，提供最基本的动画效果。接口方面和CABasicAniamtion很相似，使用可以提供初始值fromValue，这个 终点值toValue，动画时长duration以及决定动画节奏的timingFunction。其创建方式：

POPBasicAnimation *basicAnimation = [POPBasicAnimation animation];  // 创建动画

POPSpringAnimation 弹簧动画是Bezier曲线无法表述的，所以无法使用PopBasicAniamtion来实现。PopSpringAnimation便是专门用来实现弹簧动画的

POPSpringAnimation *springAnimation = [POPSpringAnimation animation];springAnimation.velocity=@(1000);       // change of value units per second每秒都改变属性springAnimation.springBounciness=14;    // value between 0-20 default at 4值的范围是0~20 默认为4springAnimation.springSpeed=3;          // value between 0-20 default at 4

POPDecayAnimation基于Bezier曲线的timingFuntion同样无法表述Decay Aniamtion，所以Pop就单独实现了一个 PopDecayAnimation，用于衰减动画。衰减动画一个很常见的地方就是 UIScrollView 滑动松开后的减速当滑动手势结束时，根据结束的加速度，给衰减动画一个初始的velocity，用来决定衰减的时长。

POPDecayAnimation *decayAnimation=[POPDecayAnimation animation];decayAnimation.velocity=@(233);    //change of value units per seconddecayAnimation.deceleration=.833;  //range of 0 to 1

POPCustomAnimation继承自PopAnimation用于创建自定义动画用的，通过POPCustomAnimationBlock类型的block进行初始化.

typedef BOOL (^POPCustomAnimationBlock)(id target, POPCustomAnimation *animation);

此block会在界面的每一帧更新的时候被调用，创建者需要在block中根据当前currentTime和elapsedTime来决定如何更新target的相关属性，以实现特定的动画。当你需要结束动画的时候就在block中返回NO，否则返回YES。

2.选择你的动画属性

在创建动画的时候，我们可以直接选择动画的属性，例如

 POPBasicAnimation *anim = [POPBasicAnimation animationWithPropertyNamed:kPOPLayerScaleXY];  // 这里修改的是视图的XY上的缩放属性

View Properties 视图属性：

• Alpha - kPOPViewAlpha
• Color - kPOPViewBackgroundColor
• Size - kPOPViewBounds
• Center - kPOPViewCenter
• Location & Size - kPOPViewFrame
• Size - kPOPViewScaleXY
• Size(Scale) - kPOPViewSize

Layer Properties 层属性

• Color - kPOPLayerBackgroundColor
• Size - kPOPLayerBounds
• Size - kPOPLayerScaleXY
• Size - kPOPLayerSize
• Opacity - kPOPLayerOpacity
• Position - kPOPLayerPosition
• X Position - kPOPLayerPositionX
• Y Position - kPOPLayerPositionY
• Rotation - kPOPLayerRotation
• Color - kPOPLayerBackgroundColor

3.设置时间曲线

basicAnimation.timingFunction=[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear];    // kCAMediaTimingFunctionLinear  kCAMediaTimingFunctionEaseIn  kCAMediaTimingFunctionEaseOut  kCAMediaTimingFunctionEaseInEaseOut // 时间类型显示

• kCAMediaTimingFunctionLinear // 属性随时间均匀变化
• kCAMediaTimingFunctionEaseIn // 先慢后快
• kCAMediaTimingFunctionEaseOut // 先快后慢
• kCAMediaTimingFunctionEaseInEaseOut // S形变化

该设置在POPDecayAnimation、POPSpringAnimation中是不起效果的。

4.设置属性变化值

View Properties：

Alpha - kPOPViewAlpha

POPBasicAnimation *basicAnimation = [POPBasicAnimation animation];basicAnimation.property = [POPAnimatableProperty propertyWithName:kPOPViewAlpha];basicAnimation.toValue= @(0); // scale from 0 to 1 缩放的范围0~1

Color - kPOPViewBackgroundColor

POPSpringAnimation *basicAnimation = [POPSpringAnimation animation];basicAnimation.property = [POPAnimatableProperty propertyWithName: kPOPLayerBackgroundColor];basicAnimation.toValue= [UIColor redColor];

Size - kPOPViewBounds

POPBasicAnimation *basicAnimation = [POPBasicAnimation animation];basicAnimation.property = [POPAnimatableProperty propertyWithName:kPOPViewBounds];basicAnimation.toValue=[NSValue valueWithCGRect:CGRectMake(0, 0, 90, 190)]; //first 2 values dont matter

Center - kPOPViewCenter

POPBasicAnimation *basicAnimation = [POPBasicAnimation animation];basicAnimation.property = [POPAnimatableProperty propertyWithName:kPOPViewCenter];basicAnimation.toValue=[NSValue valueWithCGPoint:CGPointMake(200, 200)];

Location & Size - kPOPViewFrame

POPBasicAnimation *basicAnimation = [POPBasicAnimation animation];basicAnimation.property = [POPAnimatableProperty propertyWithName:kPOPViewFrame];basicAnimation.toValue=[NSValue valueWithCGRect:CGRectMake(140, 140, 140, 140)];

Size - kPOPViewScaleXY

POPBasicAnimation *basicAnimation = [POPBasicAnimation animation];basicAnimation.property = [POPAnimatableProperty propertyWithName:kPOPViewScaleXY];basicAnimation.toValue=[NSValue valueWithCGSize:CGSizeMake(3, 2)];

Size(Scale) - kPOPViewSize

POPBasicAnimation *basicAnimation = [POPBasicAnimation animation];basicAnimation.property = [POPAnimatableProperty propertyWithName:kPOPViewSize];basicAnimation.toValue=[NSValue valueWithCGSize:CGSizeMake(30, 200)];

Layer Properties

Color - kPOPLayerBackgroundColor

POPSpringAnimation *basicAnimation = [POPSpringAnimation animation];basicAnimation.property = [POPAnimatableProperty propertyWithName: kPOPLayerBackgroundColor];basicAnimation.toValue= [UIColor redColor];

Size - kPOPLayerBounds

POPSpringAnimation *basicAnimation = [POPSpringAnimation animation];basicAnimation.property = [POPAnimatableProperty propertyWithName: kPOPLayerBounds];basicAnimation.toValue= [NSValue valueWithCGRect:CGRectMake(0, 0, 90, 90)]; //first 2 values dont matter

Size - kPOPLayerScaleXY

POPBasicAnimation *basicAnimation = [POPBasicAnimation animation];basicAnimation.property = [POPAnimatableProperty propertyWithName: kPOPLayerScaleXY];basicAnimation.toValue= [NSValue valueWithCGSize:CGSizeMake(2, 1)];//increases width and height scales

Size - kPOPLayerSize

POPBasicAnimation *basicAnimation = [POPBasicAnimation animation];basicAnimation.property = [POPAnimatableProperty propertyWithName:kPOPLayerSize];basicAnimation.toValue= [NSValue valueWithCGSize:CGSizeMake(200, 200)];

Opacity - kPOPLayerOpacity

POPSpringAnimation *basicAnimation = [POPSpringAnimation animation];basicAnimation.property = [POPAnimatableProperty propertyWithName: kPOPLayerOpacity];basicAnimation.toValue = @(0);

Position - kPOPLayerPosition

POPSpringAnimation *basicAnimation = [POPSpringAnimation animation];basicAnimation.property = [POPAnimatableProperty propertyWithName: kPOPLayerPosition];basicAnimation.toValue= [NSValue valueWithCGRect:CGRectMake(130, 130, 0, 0)];//last 2 values dont matter

X Position - kPOPLayerPositionX

POPSpringAnimation *basicAnimation = [POPSpringAnimation animation];basicAnimation.property = [POPAnimatableProperty propertyWithName: kPOPLayerPositionX];basicAnimation.toValue= @(240);

Y Position - kPOPLayerPositionY

POPSpringAnimation *anim = [POPSpringAnimation animation];anim.property=[POPAnimatableProperty propertyWithName:kPOPLayerPositionY];anim.toValue = @(320);

Rotation - kPOPLayerRotation

POPSpringAnimation *basicAnimation = [POPSpringAnimation animation];basicAnimation.property = [POPAnimatableProperty propertyWithName: kPOPLayerRotation];basicAnimation.toValue= @(M_PI/4); //2 M_PI is an entire rotation

5.设置代理和名字

basicAnimation.name=@"animationName"; // 这个名字根据自己的需要来添加basicAnimation.delegate=self;

代理实现一下来监听动画执行状态：

Declare Delegate Protocol 声明代理协议
Delegate Methods 代理方法

- (void)animatorWillAnimate:(POPAnimator *)animator;将要执行动画的方法- (void)animatorDidAnimate:(POPAnimator *)animator;执行完动画的方法

在这里我们就可以根据动画的执行状态做一些我们自己的业务了，当然我们同样可以通过block的方式来实现。

例如：

   anim.completionBlock = ^(POPAnimation *anim, BOOL finished) {        if (finished) {            // do something here        }    };

6.选择动画的添加位置

例如：

[self.tableView pop_addAnimation:basicAnimation forKey:@"WhatEverNameYouWant"];

其实这一步的Key也就是我们上一步设置的Name属性，设置该名字以后，在代理方法中我们就可以根据Name值来区别动画，然后根据不同的动画执行我们需要的代码。

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总结：Pop Animation应用于CALayer时，在动画运行的任何时刻，layer和其presentationLayer的相关属性值始终保持一致，而Core Animation做不到。Pop Animation可以应用任何NSObject的对象，而Core Aniamtion必须是CALayer。