iOS 动画

####UIView 之animation s = vt; 这个是我对动画的理解， 任何动画均可以用这个来解释分析。 咱们设置一个动画 每每是限定了 运动变化(轨迹)和时间，最多见的是 

[UIView beginAnimations:nil context:NULL];
[UIView setAnimationDuration:0.30];//时间
[UIView setAnimationDelegate:self];
self.transform = rotationTransform;//视图改变
[UIView commitAnimations];

或者

[UIView animateWithDuration:0.3 animations:^{
       
        }];
```        
UIView animateWithDuration:… 这个方法 apple也作了不少的扩展，对一些简单的单一需求也能知足。
这边对下面这个带有阻尼效果的动画作个简单分析

+ (void)animateWithDuration:(NSTimeInterval)duration                      delay:(NSTimeInterval)delay     usingSpringWithDamping:(CGFloat)dampingRatio      initialSpringVelocity:(CGFloat)velocity                    options:(UIViewAnimationOptions)options                 animations:(void (^)(void))animations                  completion:(void (^)(BOOL finished))completion

usingSpringWithDamping（阻尼系数）
的范围为0.0f
到1.0f
，数值越小「弹簧」的振动效果越明显。initialSpringVelocity（初始运动速度），数值越大一开始移动速度越快。

UIView还有一种在实际开发过程当中比较常见的转场动画：

• (void)transitionWithView:(UIView *)view duration:(NSTimeInterval)duration options:(UIViewAnimationOptions)options animations:(void (^ __nullable)(void))animations completion:(void (^ __nullable)(BOOL finished))completion

如自定义拍照或录制视频功能时，在点击先后摄像头图标 视图内的画面旋转天然切换，图片集浏览。

UIViewAnimationOptions:
    UIViewAnimationOptionTransitionNone            = 0 << 20, //default
    UIViewAnimationOptionTransitionFlipFromLeft    = 1 << 20,  
    UIViewAnimationOptionTransitionFlipFromRight   = 2 << 20,
    UIViewAnimationOptionTransitionCurlUp          = 3 << 20,
    UIViewAnimationOptionTransitionCurlDown        = 4 << 20,
    UIViewAnimationOptionTransitionCrossDissolve   = 5 << 20,
    UIViewAnimationOptionTransitionFlipFromTop     = 6 << 20,
    UIViewAnimationOptionTransitionFlipFromBottom  = 7 << 20,


####UILayer之CAAnimation

@interface CAAnimation : NSObject <NSCoding, NSCopying, CAMediaTiming, CAAction>

从上看出CAAnimation 使用了CAMediaTiming协议，能够设置动画的开始时间、持续时间、速度、重复次数等，使用了CAAction协议，能够设置动画的方式（路径）来显示动画。
 CAAnimation 设置动画原理和UIView差很少，CAAnimation是做用于Layer层上的，而UIView animation 是做用于View上的。 
CAAnimation的一些派生类:
     CATransition 提供渐变效果:(推拉push效果,消退fade效果,揭开reveal效果)
     CAAnimationGroup 容许多个动画同时播放
     CABasicAnimation 提供了对单一动画的实现
     CAKeyframeAnimation 关键桢动画,能够定义行动路线

比较经常使用的是CABasicAnimation、CAKeyframeAnimation和CAAnimationGroup；
   
CABasicAnimation动画也须要设置变化和变化的时间，经过-setFromValue 和-setToValue 来指定一个开始值和结束值，duration是动画持续时间。

下面是两个例子：

• (void)showPlay{          UIColor *stroke = [UIColor redColor];     CGRect pathFrame = CGRectMake(120, 120, 60, 60);     UIBezierPath *path = [UIBezierPath bezierPathWithRoundedRect:pathFrame cornerRadius:30];          CAShapeLayer *circleShape = [CAShapeLayer layer];     circleShape.path = path.CGPath;     circleShape.position = CGPointMake(0, 0);     circleShape.fillColor = [UIColor clearColor].CGColor;     circleShape.opacity = 0;     circleShape.strokeColor = stroke.CGColor;     circleShape.lineWidth = 3;          [self.layer addSublayer:circleShape];          CABasicAnimation *scaleAnimation = [CABasicAnimation animationWithKeyPath:@"transform.scale"];     scaleAnimation.fromValue = [NSValue valueWithCATransform3D:CATransform3DIdentity];     scaleAnimation.toValue = [NSValue valueWithCATransform3D:CATransform3DMakeScale(3, 1, 1)];//x,y,z放大缩小倍数          CABasicAnimation *alphaAnimation = [CABasicAnimation animationWithKeyPath:@"opacity"];     alphaAnimation.fromValue = @1;     alphaAnimation.toValue = @0;          CAAnimationGroup *animation = [CAAnimationGroup animation];     animation.animations = @[scaleAnimation, alphaAnimation];     animation.duration = 7.5f;     animation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear];     animation.repeatCount = 4;     [circleShape addAnimation:animation forKey:nil]; }

• (void)rotateWheel:(UIView*)view {     float totalRotation = 6M_PI;          NSArray keyTimes = @[@0.0, @0.2, @0.8, @1.0]; //0-0.2-0.8-1.0 3段动画     CAKeyframeAnimation* animation = [CAKeyframeAnimation animationWithKeyPath:@"transform.rotation.z"]; //z轴选择     animation.duration = 5;     animation.keyTimes = keyTimes;     animation.values = @[@(0totalRotation), @(0.33totalRotation), @(0.67totalRotation), @(1totalRotation)];     animation.timingFunctions = @[[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear],                                   [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear],                                   [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear]];     [view.layer addAnimation:animation forKey:@"rotateZ"]; }

###### CADisplayLink
CADisplayLink 其实和CADAnimation同样 都是QuartzCore.framework里的类，但这个又是有些特殊的地方，通常都把它于NSTimer放在一块儿比较，由于这个拥有计时器的功能，精度能达到每秒触发60次。它和timer同样是把对象加到runloop中，触发的时间到了，runloop向对象指定的target发送一次selector消息。 在作一些精细点的动画，不受其余动画或线程干扰，须要指定runloop的模式，就像srollView在滚动时，若是是默认的runloop模式，timer的计时时间会延迟。

以下面一段代码：为了实现img1Loading和img2Loading 无缝隙循环移动

#pragma - mark - loadingImageAnimation

• (void)startMoveLoadingImage {     self.moveDisplaylink = [CADisplayLink displayLinkWithTarget:self selector:@selector(bgLoadingImageMove:)];     self.moveDisplaylink.frameInterval = 2;//每秒30次     [self.moveDisplaylink addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSRunLoopCommonModes];

}

• (void)bgLoadingImageMove:(CADisplayLink *)displayLink {     self.linkTimeCount ++;     int perMaxCount = 360; //每一次循环滑动调用的最大次数     [self setLoadingImage:perMaxCount];      }

• (void)setLoadingImage:(int)perMaxCount {     int moveCount = self.linkTimeCount%perMaxCount;//余数 //    CCLog(@"moveCount %d",moveCount);

    CGRect frame = _img1Loading.frame;     CGFloat imageWidth = frame.size.width - 44; //441     frame.origin.x = -imageWidth/perMaxCount*moveCount;          if (self.img1Loading.frame.origin.x > self.img2Loading.frame.origin.x) {         self.img2Loading.frame = frame;         frame.origin.x += imageWidth;         self.img1Loading.frame = frame;     }     else     {         self.img1Loading.frame = frame;         frame.origin.x += imageWidth;         self.img2Loading.frame = frame;     }          if (moveCount+1 == perMaxCount)     {         self.isNeedChange = YES;     }     if (self.isNeedChange) {         frame.origin.x = imageWidth;         if (self.img1Loading.frame.origin.x > self.img2Loading.frame.origin.x) {             self.img2Loading.frame = frame;         }         else         {             self.img1Loading.frame = frame;         }         self.isNeedChange = false;     }

}

• (void)stopAnimation {     if (_moveDisplaylink)     {         [self.moveDisplaylink invalidate];         self.moveDisplaylink = nil;         self.linkTimeCount = 0;     } }