首先让我们了解下什么是 Core Animation，Core Animation 为核心动画，他为图形渲染和动画提供了基础。使用核心动画，我们只需要设置起点、终点、关键帧等一些参数，剩下的工作核心动画会自动帮我们处理。（学过 Flash 的朋友会有种似曾相识的感觉）
核心动画开发动画的本质是将 CALayer 中的内容转换为位图从而供硬件操作，他不用消耗 CPU 资源，合理使用他能提高 App 性能。
核心动画的几大核心类：
CAAnimation「核心动画基类」：不能直接使用，他遵循并实现了 CAMediaTiming 协议，负责动画运行时间和速度的控制。
CAPropertyAnimation「属性动画基类」：不能直接使用，他通过可动画属性进行动画设置。
CAAnimationGroup「动画组」：他是一种组合模式，可以组合多个动画进行动画行为的统一控制。
CATransition「转场动画」：主要通过滤镜进行动画效果设置。
CABasicAnimation「基础动画」：通过起点和终点状态属性参数进行动画控制。
CAKeyframeAnimation「关键帧动画」：同 CABasicAnimation 一样通过属性参数进行动画控制，但不同的是他可以有多个状态控制，不单单只有起点和终点。
CABasicAnimation 和 CAKeyframeAnimation 都属于 CAPropertyAnimation，他们通过修改属性参数产生动画效果。在两个状态点中间过程的动画，可以称为「补间动画」，他由系统自动计算产生。CABasicAnimation 只有起点和终点状态，从某种角度来说，他相当于有两个关键帧的 CAKeyframeAnimation。
下面让我们通过例子，了解如何使用 CAKeyframeAnimation「关键帧动画」、CABasicAnimation「基础动画」、CAAnimationGroup「动画组」吧。
效果如下：
ViewController.h
1 #import <UIKit/UIKit.h> 2 3 @interface ViewController : UIViewController 4 @property (strong, nonatomic) IBOutlet UIImageView *imgVAnimation; 5 @property (strong, nonatomic) IBOutlet UIButton *btnAnimation1; 6 @property (strong, nonatomic) IBOutlet UIButton *btnAnimation2; 7 8 @end
ViewController.m
1 #import "ViewController.h" 2 3 @interface ViewController () 4 - (void)modifyLayerForButton:(UIButton *)btn; 5 - (void)layoutUI; 6 @end 7 8 @implementation ViewController 9 #define kCornerRadiusOfImage CGRectGetWidth(_imgVAnimation.frame)/2.0 10 11 - (void)viewDidLoad { 12 [super viewDidLoad]; 13 14 [self layoutUI]; 15 } 16 17 - (void)didReceiveMemoryWarning { 18 [super didReceiveMemoryWarning]; 19 // Dispose of any resources that can be recreated. 20 } 21 22 - (void)modifyLayerForButton:(UIButton *)btn { 23 btn.layer.masksToBounds = YES; 24 btn.layer.cornerRadius = 5.0; 25 btn.layer.borderColor = [UIColor grayColor].CGColor; 26 btn.layer.borderWidth = 1.0; 27 } 28 29 - (void)layoutUI { 30 //图片视图 31 _imgVAnimation.layer.masksToBounds = YES; 32 _imgVAnimation.layer.cornerRadius = kCornerRadiusOfImage; 33 _imgVAnimation.layer.borderColor = [UIColor orangeColor].CGColor; 34 _imgVAnimation.layer.borderWidth = 2.0; 35 36 //按钮 37 [self modifyLayerForButton:_btnAnimation1]; 38 [self modifyLayerForButton:_btnAnimation2]; 39 } 40 41 - (IBAction)btnAnimation1DidPush:(id)sender { 42 //移到右下角；使用关键帧动画，移动路径为预定的贝塞尔曲线路径 43 CGPoint fromPoint = _imgVAnimation.center; 44 CGFloat toPointX = self.view.frame.size.width - kCornerRadiusOfImage; 45 CGFloat toPointY = self.view.frame.size.height - kCornerRadiusOfImage; 46 CGPoint toPoint = CGPointMake(toPointX, toPointY); 47 CGPoint controlPoint = CGPointMake(toPointX, 0.0); 48 49 UIBezierPath *path = [UIBezierPath bezierPath]; 50 [path moveToPoint:fromPoint]; 51 [path addQuadCurveToPoint:toPoint controlPoint:controlPoint]; 52 53 CAKeyframeAnimation *positionAnimation = [CAKeyframeAnimation animationWithKeyPath:@"position"]; 54 positionAnimation.path = path.CGPath; 55 positionAnimation.removedOnCompletion = YES; 56 57 //变小；使用基础动画 58 CABasicAnimation *transformAnimation = [CABasicAnimation animationWithKeyPath:@"transform"]; 59 transformAnimation.fromValue = [NSValue valueWithCATransform3D:CATransform3DIdentity]; 60 transformAnimation.toValue = [NSValue valueWithCATransform3D:CATransform3DMakeScale(0.1, 0.1, 1.0)]; //设置 X 轴和 Y 轴缩放比例都为1.0，而 Z 轴不变 61 transformAnimation.removedOnCompletion = YES; 62 63 //透明；使用基础动画 64 CABasicAnimation *opacityAnimation = [CABasicAnimation animationWithKeyPath:@"opacity"]; 65 opacityAnimation.fromValue = [NSNumber numberWithFloat:1.0]; 66 opacityAnimation.toValue = [NSNumber numberWithFloat:0.1]; 67 opacityAnimation.removedOnCompletion = YES; 68 69 //组合效果；使用动画组 70 CAAnimationGroup *animationGroup = [CAAnimationGroup animation]; 71 animationGroup.animations = @[ positionAnimation, transformAnimation, opacityAnimation ]; 72 animationGroup.duration = 1.0; //设置动画执行时间；这里设置为1.0秒 73 animationGroup.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseIn]; //设置媒体调速运动；默认为 kCAMediaTimingFunctionLinear，即为线型间隔；这里设置为 kCAMediaTimingFunctionEaseIn，即先慢后快，相当于有个加速度 74 animationGroup.autoreverses = YES; //设置自动倒退，即动画回放；默认值为NO 75 [_imgVAnimation.layer addAnimation:animationGroup forKey:nil]; 76 } 77 78 - (IBAction)btnAnimation2DidPush:(id)sender { 79 //向右移动；使用关键帧动画，移动路径为预定的直线路径 80 CGPoint fromPoint = _imgVAnimation.center; 81 CGPoint toPoint = CGPointMake(fromPoint.x + 100.0, fromPoint.y); 82 83 UIBezierPath *path = [UIBezierPath bezierPath]; 84 [path moveToPoint:fromPoint]; 85 [path addLineToPoint:toPoint]; 86 87 CAKeyframeAnimation *positionAnimation = [CAKeyframeAnimation animationWithKeyPath:@"position"]; 88 positionAnimation.path = path.CGPath; 89 positionAnimation.removedOnCompletion = YES; 90 91 //旋转；使用基础动画 92 CABasicAnimation *transformAnimation = [CABasicAnimation animationWithKeyPath:@"transform"]; 93 transformAnimation.fromValue = [NSValue valueWithCATransform3D:CATransform3DIdentity]; 94 transformAnimation.toValue = [NSValue valueWithCATransform3D:CATransform3DMakeRotation(M_PI_2, 0.0, 0.0, 1.0)]; //设置沿着 Z 轴顺时针旋转90度；注意 CATransform3DMakeRotation 总是按最短路径来选择，当顺时针和逆时针的路径相同时（e.g. M_PI），会使用逆时针 95 transformAnimation.repeatCount = 8.0; //设置动画播放重复次数；这里设置为8.0次，共720度 96 transformAnimation.duration = 0.5; //设置动画执行时间；这里设置为0.5秒 97 transformAnimation.cumulative = YES; //设置是否累积；默认值为NO，这里设置为YES，看起来才动画效果连贯 98 transformAnimation.removedOnCompletion = YES; 99 100 //组合效果；使用动画组 101 CAAnimationGroup *animationGroup = [CAAnimationGroup animation]; 102 animationGroup.animations = @[ positionAnimation, transformAnimation ]; 103 animationGroup.duration = 4.0; //设置动画执行时间；这里设置为4.0秒 104 animationGroup.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseIn]; //设置媒体调速运动；默认为 kCAMediaTimingFunctionLinear，即为线型间隔；这里设置为 kCAMediaTimingFunctionEaseIn，即先慢后快，相当于有个加速度 105 animationGroup.autoreverses = YES; //设置自动倒退，即动画回放；默认值为NO 106 107 //以下两句是『动画结束后回到初始状态的现象』的解决方法；这里没用到 108 //animationGroup.removedOnCompletion = NO; //设置是否完成后从对应的所属图层移除他，默认为YES 109 //animationGroup.fillMode = kCAFillModeForwards; //设置动画填充模式；默认值为 kCAFillModeRemoved，即动画执行完就移除，变回原来的状态，这里设置为 kCAFillModeForwards，即保持向前的状态 110 [_imgVAnimation.layer addAnimation:animationGroup forKey:nil]; 111 } 112 113 @end
Main.storyboard
1 <?xml version="1.0" encoding="UTF-8" standalone="no"?> 2 <document type="com.apple.InterfaceBuilder3.CocoaTouch.Storyboard.XIB" version="3.0" toolsVersion="7706" systemVersion="14E46" targetRuntime="iOS.CocoaTouch" propertyAccessControl="none" useAutolayout="YES" useTraitCollections="YES" initialViewController="vXZ-lx-hvc"> 3 <dependencies> 4 <deployment identifier="iOS"/> 5 <plugIn identifier="com.apple.InterfaceBuilder.IBCocoaTouchPlugin" version="7703"/> 6 </dependencies> 7 <scenes> 8 <!--View Controller--> 9 <scene sceneID="ufC-wZ-h7g"> 10 <objects> 11 <viewController id="vXZ-lx-hvc" customClass="ViewController" sceneMemberID="viewController"> 12 <layoutGuides> 13 <viewControllerLayoutGuide type="top" id="jyV-Pf-zRb"/> 14 <viewControllerLayoutGuide type="bottom" id="2fi-mo-0CV"/> 15 </layoutGuides> 16 <view key="view" contentMode="scaleToFill" id="kh9-bI-dsS"> 17 <rect key="frame" x="0.0" y="0.0" width="600" height="600"/> 18 <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMaxY="YES"/> 19 <subviews> 20 <imageView userInteractionEnabled="NO" contentMode="scaleToFill" horizontalHuggingPriority="251" verticalHuggingPriority="251" fixedFrame="YES" image="Emoticon_tusiji_icon2" translatesAutoresizingMaskIntoConstraints="NO" id="j2r-O5-Hj2"> 21 <rect key="frame" x="20" y="40" width="150" height="150"/> 22 </imageView> 23 <button opaque="NO" contentMode="scaleToFill" fixedFrame="YES" contentHorizontalAlignment="center" contentVerticalAlignment="center" buttonType="roundedRect" lineBreakMode="middleTruncation" translatesAutoresizingMaskIntoConstraints="NO" id="aiO-kP-xCF"> 24 <rect key="frame" x="20" y="243" width="150" height="50"/> 25 <state key="normal" title="移到右下角变小透明"> 26 <color key="titleShadowColor" white="0.5" alpha="1" colorSpace="calibratedWhite"/> 27 </state> 28 <connections> 29 <action selector="btnAnimation1DidPush:" destination="vXZ-lx-hvc" eventType="touchUpInside" id="7Z2-yc-1vS"/> 30 </connections> 31 </button> 32 <label opaque="NO" userInteractionEnabled="NO" contentMode="left" horizontalHuggingPriority="251" verticalHuggingPriority="251" fixedFrame="YES" text="图片操作：" lineBreakMode="tailTruncation" baselineAdjustment="alignBaselines" adjustsFontSizeToFit="NO" translatesAutoresizingMaskIntoConstraints="NO" id="YH5-Oi-KEH"> 33 <rect key="frame" x="20" y="208" width="150" height="21"/> 34 <fontDescription key="fontDescription" type="boldSystem" pointSize="17"/> 35 <color key="textColor" cocoaTouchSystemColor="darkTextColor"/> 36 <nil key="highlightedColor"/> 37 </label> 38 <button opaque="NO" contentMode="scaleToFill" fixedFrame="YES" contentHorizontalAlignment="center" contentVerticalAlignment="center" buttonType="roundedRect" lineBreakMode="middleTruncation" translatesAutoresizingMaskIntoConstraints="NO" id="hSL-o5-Ism"> 39 <rect key="frame" x="20" y="311" width="150" height="50"/> 40 <state key="normal" title="旋转并向右移动"> 41 <color key="titleShadowColor" white="0.5" alpha="1" colorSpace="calibratedWhite"/> 42 </state> 43 <connections> 44 <action selector="btnAnimation2DidPush:" destination="vXZ-lx-hvc" eventType="touchUpInside" id="lC4-zx-uIb"/> 45 </connections> 46 </button> 47 </subviews> 48 <color key="backgroundColor" white="1" alpha="1" colorSpace="custom" customColorSpace="calibratedWhite"/> 49 </view> 50 <connections> 51 <outlet property="btnAnimation1" destination="aiO-kP-xCF" id="kSp-82-S2R"/> 52 <outlet property="btnAnimation2" destination="hSL-o5-Ism" id="6Mz-Wd-xfN"/> 53 <outlet property="imgVAnimation" destination="j2r-O5-Hj2" id="Gmp-iW-kaX"/> 54 </connections> 55 </viewController> 56 <placeholder placeholderIdentifier="IBFirstResponder" id="x5A-6p-PRh" sceneMemberID="firstResponder"/> 57 </objects> 58 </scene> 59 </scenes> 60 <resources> 61 <image name="Emoticon_tusiji_icon2" width="150" height="150"/> 62 </resources> 63 </document>