前一篇總結了Core Animation的一些基礎知識，這一篇主要是Core Animation 的一些應用，涉及到CAShapeLayer、CAReplicatorLayer等圖層的知識。
先看效果圖：
1、切換圖片：
2、彩票轉盤
3、圖片折疊
4、進度條旋轉
5、粒子效果
一、切換圖片
看起來很復雜的動畫，通過少量的計算和編碼就可以簡單的實現。要做到這一步，必須是需要研究iOS開發中的Core Animation和Core Graphics框架的。日常工作中，對于很多東西不求甚解，只是拿過來用，甚至都不研究、封裝一下別人代碼，這種做法是很不好的。我喜歡自己造輪子，輪子造多了，開發經驗與思維也就提升上去了。
這個動畫實現是比較簡單的，利用了CABasicAnimation、CAKeyframeAnimation和CAAnimationGroup?？此剖莾蓮垐D片各自有著自己不同的動畫，實際不過是一個動畫方法，其平移方向與旋轉角度的不同。
我是用了CABasicAnimation設置了view的zPosition值，CAKeyframeAnimation對象設計了圖片的位移與旋轉動畫，然后將之放到CAAnimationGroup對象里面，開始動畫。
這里有一個注意點，那就是Core Animation設置的動畫位移、旋轉、縮放都只是一個假象，實際上的view該怎么還是怎么樣，并未真正有過變化。所以，在動畫結束后，想要正確的效果，那么需要設置view的zPosition值，這個值越大，view越在前面（z軸方向上的“前面”）。
代碼：
#import "ViewController.h"@interface ViewController ()@property (nonatomic, strong) NSMutableArray *images;@property (nonatomic, assign) int currentIndex;@property (weak, nonatomic) IBOutlet UIImageView *currentImageView;@property (weak, nonatomic) IBOutlet UIImageView *behindImageView;@end@implementation ViewController- (NSMutableArray *)images{if (_images == nil) {_images = [NSMutableArray array];for (int i = 1; i <= 7; i++) {UIImage *image = [UIImage imageNamed: [NSString stringWithFormat:@"%d",i]];[_images addObject:image];}}return _images;}- (void)viewDidLoad{[super viewDidLoad];self.currentIndex = 0;self.currentImageView.image = self.images[_currentIndex];}- (void)addAnimateWithPoint:(CGPoint )point angle:(CGFloat)angle fromZ:(CGFloat)fromZ toZ:(CGFloat)toZ view:(UIView *)view{CABasicAnimation *zPosition = [[CABasicAnimation alloc] init];zPosition.keyPath = @"zPosition";zPosition.fromValue = @(fromZ);zPosition.toValue = @(toZ);zPosition.duration = 1.2;CAKeyframeAnimation *rotation = [[CAKeyframeAnimation alloc] init];rotation.keyPath = @"transform.rotation";rotation.values = @[@(0), @(angle), @(0)];rotation.duration = 2;rotation.timingFunctions = @[[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut],[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut]];CAKeyframeAnimation *position = [[CAKeyframeAnimation alloc] init];position.keyPath = @"position";// CGPointMake(110, -20)position.values = @[[NSValue valueWithCGPoint:CGPointZero],[NSValue valueWithCGPoint:point],[NSValue valueWithCGPoint:CGPointZero]];position.timingFunctions = @[[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut],[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut]];position.additive = YES;position.duration = 1.2;CAAnimationGroup *animateGroup = [[CAAnimationGroup alloc] init];animateGroup.animations = @[zPosition, rotation, position];// animateGroup.beginTime = 0.5;animateGroup.delegate = self;animateGroup.duration = 1.2;[animateGroup setValue:view forKey:@"view"];[view.layer addAnimation:animateGroup forKey:nil]; view.layer.zPosition = toZ;}- (void)animationDidStop:(CAAnimation *)anim finished:(BOOL)flag{CAAnimationGroup *group = [anim valueForKey:@"view"];if (group != nil) {self.currentImageView.image = self.images[_currentIndex];self.currentImageView.layer.zPosition = 1;self.behindImageView.image = nil;self.behindImageView.layer.zPosition = -1;}}- (IBAction)previous:(id)sender {self.currentIndex = (self.currentIndex + 1) % self.images.count;self.behindImageView.image = self.images[_currentIndex];[self addAnimateWithPoint:CGPointMake(-90, 20) angle:0.15 fromZ:-1 toZ:1 view:self.behindImageView];[self addAnimateWithPoint:CGPointMake(90, -20) angle:-0.15 fromZ:1 toZ:-1 view:self.currentImageView];}- (IBAction)next:(id)sender {self.currentIndex = (self.currentIndex + 6) % self.images.count;self.behindImageView.image = self.images[_currentIndex];[self addAnimateWithPoint:CGPointMake(-90, 20) angle:-0.15 fromZ:-1 toZ:1 view:self.behindImageView];[self addAnimateWithPoint:CGPointMake(90, -20) angle:0.15 fromZ:1 toZ:-1 view:self.currentImageView];}@end二、彩票轉盤
這個動畫的實現主要難點在于Button的擺放，只要擺放好button，其他就是簡單的添加動畫的一個過程。
12個星座，那么需要12個button。在擺放它們的時候，我是將一個個button的anchorPoint設置為(0.5, 1)，將button的position設置為中心圓的圓心，然后設置transform來旋轉它們，是的達到圍繞一個圓擺放的目的。
需要知道的是，一般來說，控件的anchorPoint就是控件的中心點，所以在我們做旋轉、平移等操作的時候，也就是在圍繞中心點的一系列操作。但是，很多時候，只是圍繞中心點來設置動畫的話，會很復雜，CALayer提供了一個anchorPoint屬性，可以讓我們自由的改變其數值，從而實現比較復雜的動畫。
還有就是button的點擊事件，事實上由于一個扇形區域是上邊大，下邊小，要是不做相應的限制，當用戶點擊下面的區域時，很可能不是選中當前的button，因此要做一定的限制。這里我是自定義了一個button，在里面重寫了hitTest: WwthEvent: 方法，這個方法可以設置你所要監聽事件的區域范圍。
代碼：
#import "ZYWheelView.h"#define ZYImageW 40#define ZYImageH 46@interface ZYButton : UIButton@end@implementation ZYButton/*** 重寫此方法，截取button的點擊**/- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event{CGFloat btnW = self.bounds.size.width;CGFloat btnH = self.bounds.size.height;CGFloat x = 0;CGFloat y = btnH / 2;CGFloat w = btnW;CGFloat h = y;CGRect rect = CGRectMake(x, y, w, h);if (CGRectContainsPoint(rect, point)) {return nil;}else{return [super hitTest:point withEvent:event];}}- (CGRect)imageRectForContentRect:(CGRect)contentRect{CGFloat imageX = (contentRect.size.width - ZYImageW ) * 0.5;CGFloat imageY = 18;return CGRectMake(imageX, imageY, ZYImageW, ZYImageH);}- (void)setHighlighted:(BOOL)highlighted{ }@end@interface ZYWheelView ()@property (weak, nonatomic) IBOutlet UIImageView *wheelView;@property (nonatomic, weak) UIButton *lastSelectedBtn;@property (nonatomic, strong) CADisplayLink *timer;@end@implementation ZYWheelView+ (instancetype)wheelView{return [[[NSBundle mainBundle] loadNibNamed:@"ZYWheelView" owner:nil options:nil] lastObject];}- (void)awakeFromNib{self.wheelView.userInteractionEnabled = YES;CGFloat angle = 2 * M_PI / 12.0;UIImage *normalImage = [UIImage imageNamed:@"LuckyAstrology"];UIImage *selectedImage = [UIImage imageNamed:@"LuckyAstrologyPressed"];for (int bi = 0; bi < 12; bi++) {ZYButton *btn = [[ZYButton alloc] init];[btn setBackgroundImage:[UIImage imageNamed:@"LuckyRototeSelected"] forState:UIControlStateSelected];// 切割圖片,將切割好的圖片設置到按鈕上// CGImage中rect是當做像素來使用// UIKit 中是點坐標系// 坐標系的特點:如果在非retain屏上 1個點等于1個像素// 在retain屏上1個點等于2個像素CGFloat imageH = ZYImageH * [UIScreen mainScreen].scale;CGFloat imageW = ZYImageW * [UIScreen mainScreen].scale;CGFloat imageY = 0;CGFloat imageX = bi * imageW;CGRect rect = CGRectMake(imageX, imageY, imageW, imageH);CGImageRef normalRef = CGImageCreateWithImageInRect(normalImage.CGImage, rect);CGImageRef selectedRef = CGImageCreateWithImageInRect(selectedImage.CGImage, rect);[btn setImage:[UIImage imageWithCGImage:normalRef] forState:UIControlStateNormal];[btn setImage:[UIImage imageWithCGImage:selectedRef] forState:UIControlStateSelected];btn.bounds = CGRectMake(0, 0, 58, 143);btn.layer.anchorPoint = CGPointMake(0.5, 1);btn.layer.position = CGPointMake(self.frame.size.width * 0.5, self.frame.size.height * 0.5);btn.transform = CGAffineTransformMakeRotation(angle * bi);[btn addTarget:self action:@selector(clickBtn:) forControlEvents:UIControlEventTouchUpInside];[self.wheelView addSubview:btn];}[self startRotating];}- (void)startRotating{if (self.timer) return;self.timer = [CADisplayLink displayLinkWithTarget:self selector:@selector(updateTimer)];[self.timer addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSRunLoopCommonModes];}- (void)stopRotating{[self.timer invalidate];self.timer = nil;}- (void)clickBtn:(UIButton *)btn{self.lastSelectedBtn.selected = NO;btn.selected = YES;self.lastSelectedBtn = btn;}- (IBAction)clickCenterBtn:(id)sender {self.userInteractionEnabled = NO;[self stopRotating];CABasicAnimation *basicAnimation = [CABasicAnimation animationWithKeyPath:@"transform.rotation"];basicAnimation.toValue = @(M_PI * 2 * 5);basicAnimation.duration = 2;basicAnimation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];// basicAnimation.removedOnCompletion = NO;// basicAnimation.fillMode = kCAFillModeForwards;basicAnimation.delegate = self;[self.wheelView.layer addAnimation:basicAnimation forKey:nil];}- (void)animationDidStop:(CAAnimation *)anim finished:(BOOL)flag{self.userInteractionEnabled = YES;// 根據選中的按鈕獲取旋轉的度數,// 通過transform獲取角度CGFloat angle = atan2(self.lastSelectedBtn.transform.b, self.lastSelectedBtn.transform.a);// 從實際上旋轉轉盤self.wheelView.transform = CGAffineTransformMakeRotation(-angle);dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(1 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{[self startRotating];}); }- (void)updateTimer{self.wheelView.transform = CGAffineTransformRotate(self.wheelView.transform, M_PI / 200);}- (void)dealloc{[self stopRotating];}@end3、圖片折疊
這個效果看起來很炫酷，但實際做起來是比較簡單的。需要三個View，兩個UIImageView，一個接受拖拽action的View。CALayer里面有個contentRect屬性，它可以設置layer里面的顯示內容，利用這個屬性，我們可以做在下載圖片時，下載一點展示一點的效果。 在這里，我用這個屬性來這是兩張UIImageView各自展示一半的圖片，然后將這兩張ImageView拼接在一起，顯示完整的圖片。
在一個覆蓋這張完整圖片的View上添加拖拽手勢，以實現動畫過程。
這里有一個新的圖層需要學習下，CAGradientLayer，它是用來做顏色漸變的，用法與CALayer的用法相似：
屬性代碼：
CAGradientLayer *gradientLayer = [CAGradientLayer layer];gradientLayer.frame = self.bottomView.bounds;gradientLayer.opacity = 0;gradientLayer.colors = @[(id)[UIColor clearColor].CGColor, (id)[UIColor blackColor].CGColor];self.gradientLayer = gradientLayer;[self.bottomView.layer addSublayer:gradientLayer];// 設置漸變顏色// gradientL.colors = @[(id)[UIColor redColor].CGColor,(id)[UIColor greenColor].CGColor,(id)[UIColor yellowColor].CGColor];// 設置漸變定位點// gradientL.locations = @[@0.1,@0.4,@0.5];// 設置漸變開始點，取值0~1// gradientL.startPoint = CGPointMake(0, 1);
設置好之后，在pan手勢的方法里面不斷改變gradientLayer的opacity即可達到想要的效果。
CATransform3D有個m34屬性，可以設置透視度，一般將這個值設置為- 1 / 500.0，特定需求可以微調這個值。
代碼：
#import "ViewController.h"@interface ViewController ()@property (weak, nonatomic) IBOutlet UIImageView *topView;@property (weak, nonatomic) IBOutlet UIImageView *bottomView;@property (weak, nonatomic) IBOutlet UIView *containView;@property (nonatomic, weak) CAGradientLayer *gradientLayer;@end@implementation ViewController- (void)viewDidLoad {[super viewDidLoad];// Do any additional setup after loading the view, typically from a nib.[self setupOtherView];//設置漸變的陰影[self setupShadow];}- (void)setupOtherView{//設置contentsRect用來表示圖片顯示的大小，可以做邊下載邊顯示的UI效果,取值是(0--1)self.topView.layer.contentsRect = CGRectMake(0, 0, 1, 0.5);self.topView.layer.anchorPoint = CGPointMake(0.5, 1);self.bottomView.layer.contentsRect = CGRectMake(0, 0.5, 1, 0.5);self.bottomView.layer.anchorPoint = CGPointMake(0.5, 0);UIPanGestureRecognizer *gesture = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(pan:)];[self.containView addGestureRecognizer:gesture];}- (void)setupShadow{CAGradientLayer *gradientLayer = [CAGradientLayer layer];gradientLayer.frame = self.bottomView.bounds;gradientLayer.opacity = 0;gradientLayer.colors = @[(id)[UIColor clearColor].CGColor, (id)[UIColor blackColor].CGColor];self.gradientLayer = gradientLayer;[self.bottomView.layer addSublayer:gradientLayer];// 設置漸變顏色// gradientL.colors = @[(id)[UIColor redColor].CGColor,(id)[UIColor greenColor].CGColor,(id)[UIColor yellowColor].CGColor];// 設置漸變定位點// gradientL.locations = @[@0.1,@0.4,@0.5];// 設置漸變開始點，取值0~1// gradientL.startPoint = CGPointMake(0, 1);}- (void)pan:(UIPanGestureRecognizer *)recognizer{CGFloat y = [recognizer translationInView:self.containView].y;if (y >= 300) y = 300;if (y <= -300) y = -300;// 旋轉角度,往下逆時針旋轉CGFloat angle = -y / 320.0 * M_PI;self.topView.layer.transform = CATransform3DIdentity;CATransform3D transfrom = CATransform3DIdentity;transfrom.m34 = -1 / 500.0;self.topView.layer.transform = CATransform3DRotate(transfrom, angle, 1, 0, 0);self.gradientLayer.opacity = y / 300.0;if (recognizer.state == UIGestureRecognizerStateEnded) {// 彈簧效果的動畫// SpringWithDamping:彈性系數,越小，彈簧效果越明顯[UIView animateWithDuration:0.5 delay:0 usingSpringWithDamping:0.3 initialSpringVelocity:11 options:UIViewAnimationOptionCurveEaseInOut animations:^{self.topView.layer.transform = CATransform3DIdentity;self.gradientLayer.opacity = 0;} completion:nil];}}@end4、旋轉進度條
圓圈旋轉一般都是放在HUD上吧。記得以前我也做過一個類似的功能，那時候還沒現在這樣的知識儲備，只能是用CAKeyframeAnimation做，讓美工做出了一根頂部是一個小白點，除此之外，很長的那部分是為clearColor的小矩形，然后我設置它的anchorPoint，給 CAKeyframeAnimation添加一個圓形的path，然后圍繞這個path旋轉，做是勉強做出來，但是很不好看吧。
現在可以有更好的選擇了，CAReplicatorLayer（復制圖層）。我們可以在復制圖層里面添加一個instance圖層，如果設置了復制圖層的instanceCount，假如讓instanceCount == 5， 那么復制圖層會自動幫我們復制5個跟instance圖層一樣的圖層（事實上，我們可以在一開始就給instance圖層設置動畫，那么在復制的時候，一樣會把動畫也復制過來），除此之外，還可以設置復制圖層里面的instance圖層的transfrom，從而實現一定的布局。復制圖層里面還有一個instanceDelay，它表示延遲多少時間開始動畫等等。
這個Demo就是用了上面所說的實現的，代碼：
#import "ViewController.h"@interface ViewController ()@property (weak, nonatomic) IBOutlet UIView *containView;@end@implementation ViewController- (void)viewDidLoad {[super viewDidLoad];// Do any additional setup after loading the view, typically from a nib.[self setupReplicatorLayerAndAnimation];}- (void)setupReplicatorLayerAndAnimation{CAReplicatorLayer *replicatorLayer = [CAReplicatorLayer layer];replicatorLayer.frame = self.containView.layer.bounds;[self.containView.layer addSublayer:replicatorLayer];CALayer *layer = [CALayer layer];layer.frame = CGRectMake(self.containView.frame.size.width * 0.5, 20, 16, 16);layer.backgroundColor = [UIColor redColor].CGColor;layer.cornerRadius = layer.frame.size.width / 2;//這一句可以將初始過程移除掉layer.transform = CATransform3DMakeScale(0, 0, 0);[replicatorLayer addSublayer:layer];replicatorLayer.instanceCount = 22;CABasicAnimation *basicAn = [CABasicAnimation animationWithKeyPath:@"transform.scale"];basicAn.fromValue = @1;basicAn.toValue = @0;basicAn.duration = 1;basicAn.repeatCount = MAXFLOAT;[layer addAnimation:basicAn forKey:nil];replicatorLayer.instanceDelay = basicAn.duration / (double)replicatorLayer.instanceCount;replicatorLayer.instanceTransform = CATransform3DMakeRotation(2 * M_PI / replicatorLayer.instanceCount, 0, 0, 1);}@end5、粒子效果
這個東西就是CAReplicatorLayer（復制圖層）和Core Graphics的結合吧，我是采用UIBezierPath來繪制線條，然后將繪制好的path賦值給小球的animation路徑，然后將小球添加到復制圖層，設置下instanceCount，設置下延遲時間，效果就出來了。
代碼：
#import "ZYDrawView.h"@interface ZYDrawView ()@property (nonatomic, strong) UIBezierPath *bezierPath;@property (nonatomic, weak) CAReplicatorLayer *replicatorLayer;@property (nonatomic, weak) CALayer *norLayer;@endstatic int _count = 0;@implementation ZYDrawView- (UIBezierPath *)bezierPath{if (_bezierPath == nil) {_bezierPath = [[UIBezierPath alloc] init];}return _bezierPath;}- (void)awakeFromNib{CAReplicatorLayer *replicatorLayer = [CAReplicatorLayer layer];replicatorLayer.frame = self.bounds;[self.layer addSublayer:replicatorLayer];CALayer *layer = [CALayer layer];layer.frame = CGRectMake(0, -200, 10, 10);layer.cornerRadius = layer.frame.size.width * 0.5;layer.backgroundColor = [UIColor redColor].CGColor;[replicatorLayer addSublayer:layer];self.replicatorLayer = replicatorLayer;self.norLayer = layer;}- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{CGPoint curPoint = [[touches anyObject] locationInView:self];[self.bezierPath moveToPoint:curPoint];}- (void)touchesMoved:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{_count++;CGPoint curPoint = [[touches anyObject] locationInView:self];[self.bezierPath addLineToPoint:curPoint];[self setNeedsDisplay];}- (void)startAnimation{CAKeyframeAnimation *keyframeAn = [CAKeyframeAnimation animationWithKeyPath:@"position"];keyframeAn.path = self.bezierPath.CGPath;keyframeAn.duration = 4;keyframeAn.repeatCount = MAXFLOAT;[self.norLayer addAnimation:keyframeAn forKey:nil];self.replicatorLayer.instanceCount = _count;self.replicatorLayer.instanceDelay = 0.1;}- (void)reDraw{_bezierPath = nil;_count = 1;[self.norLayer removeAllAnimations];[self setNeedsDisplay];}- (void)drawRect:(CGRect)rect{[self.bezierPath stroke];}@end以上內容是小編給大家介紹的Core Animation一些Demo總結 （動態切換圖片、大轉盤、圖片折疊、進度條等動畫效果），希望對大家以上幫助！
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