iOS

隐式动画vs显式动画

隐式动画

隐式动画是Core Animation框架自动完成的动画，不需要我们手动控制。支持隐式动画的CALayer属性叫Animatable Properties，苹果在这个文档中列出了所有Animatable Properties。
Tips:

  • UIView的默认layer的隐式动画是关闭的，自定义的CALayer隐式动画是开启的。
  • 隐式动画默认duration是0.25秒

在animation block中UIView的隐式动画又重新开启，比如通过以下函数：

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+animateWithDuration:animations:

禁用CALayer隐式动画方法：
1.实现CALayerDelegate，并在-actionForLayer:forKey:返回NSNull
2.通过[CATransaction setDisableActions:YES];,比如

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[CATransaction begin]
[CATransaction setDisableActions:YES];
[CATransaction commit];

显式动画

显式动画允许你对一些属性做指定的自定义动画，或创建非线性动画，比如沿着任意一条曲线移动
常见显式动画用法：
1.CABasicAnimation
随机改变colorLayer.backgroundColor动画

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- (void)applyBasicAnimation:(CABasicAnimation *)animation toLayer:(CALayer *)layer
{

    //set the from value (using presentation layer if available)
    animation.fromValue = [layer.presentationLayer ?: layer valueForKeyPath:animation.keyPath];
    //update the property in advance
    //note: this approach will only work if toValue != nil 
    [CATransaction begin];
    [CATransaction setDisableActions:YES];
    [layer setValue:animation.toValue forKeyPath:animation.keyPath];
    [CATransaction commit];
    //apply animation to layer
    [layer addAnimation:animation forKey:nil];
}

- (IBAction)changeColor
{
    //create a new random color
    CGFloat red = arc4random() / (CGFloat)INT_MAX;
    CGFloat green = arc4random() / (CGFloat)INT_MAX;
    CGFloat blue = arc4random() / (CGFloat)INT_MAX;
    UIColor *color = [UIColor colorWithRed:red green:green blue:blue alpha:1.0];
    //create a basic animation
    CABasicAnimation *animation = [CABasicAnimation animation];
    animation.keyPath = @"backgroundColor";
    animation.toValue = (__bridge id)color.CGColor;
    //apply animation without snap-back
    [self applyBasicAnimation:animation toLayer:self.colorLayer];
}

2.CAKeyframeAnimation
让飞机沿着曲线飞行

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@interface ViewController ()

@property (nonatomic, weak) IBOutlet UIView *containerView;

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    //create a path
    UIBezierPath *bezierPath = [[UIBezierPath alloc] init];
    [bezierPath moveToPoint:CGPointMake(0, 150)];
    [bezierPath addCurveToPoint:CGPointMake(300, 150) controlPoint1:CGPointMake(75, 0) controlPoint2:CGPointMake(225, 300)];
    //draw the path using a CAShapeLayer
    CAShapeLayer *pathLayer = [CAShapeLayer layer];
    pathLayer.path = bezierPath.CGPath;
    pathLayer.fillColor = [UIColor clearColor].CGColor;
    pathLayer.strokeColor = [UIColor redColor].CGColor;
    pathLayer.lineWidth = 3.0f;
    [self.containerView.layer addSublayer:pathLayer];
    //add the ship
    CALayer *shipLayer = [CALayer layer];
    shipLayer.frame = CGRectMake(0, 0, 64, 64);
    shipLayer.position = CGPointMake(0, 150);
    shipLayer.contents = (__bridge id)[UIImage imageNamed: @"Ship.png"].CGImage;
    [self.containerView.layer addSublayer:shipLayer];
    //create the keyframe animation
    CAKeyframeAnimation *animation = [CAKeyframeAnimation animation];
    animation.keyPath = @"position";
    animation.duration = 4.0;
    animation.path = bezierPath.CGPath;
  	animation.rotationMode = kCAAnimationRotateAuto;
    [shipLayer addAnimation:animation forKey:nil];
}

@end

plane

3.CAAnimationGroup
让色块沿着曲线边改变颜色，边移动

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- (void)viewDidLoad
{
    [super viewDidLoad];
    //create a path
    UIBezierPath *bezierPath = [[UIBezierPath alloc] init];
    [bezierPath moveToPoint:CGPointMake(0, 150)];
    [bezierPath addCurveToPoint:CGPointMake(300, 150) controlPoint1:CGPointMake(75, 0) controlPoint2:CGPointMake(225, 300)];
    //draw the path using a CAShapeLayer
    CAShapeLayer *pathLayer = [CAShapeLayer layer];
    pathLayer.path = bezierPath.CGPath;
    pathLayer.fillColor = [UIColor clearColor].CGColor;
    pathLayer.strokeColor = [UIColor redColor].CGColor;
    pathLayer.lineWidth = 3.0f;
    [self.containerView.layer addSublayer:pathLayer];
    //add a colored layer
    CALayer *colorLayer = [CALayer layer];
    colorLayer.frame = CGRectMake(0, 0, 64, 64);
    colorLayer.position = CGPointMake(0, 150);
    colorLayer.backgroundColor = [UIColor greenColor].CGColor;
    [self.containerView.layer addSublayer:colorLayer];
    //create the position animation
    CAKeyframeAnimation *animation1 = [CAKeyframeAnimation animation];
    animation1.keyPath = @"position";
    animation1.path = bezierPath.CGPath;
    animation1.rotationMode = kCAAnimationRotateAuto;
    //create the color animation
    CABasicAnimation *animation2 = [CABasicAnimation animation];
    animation2.keyPath = @"backgroundColor";
    animation2.toValue = (__bridge id)[UIColor redColor].CGColor;
    //create group animation
    CAAnimationGroup *groupAnimation = [CAAnimationGroup animation];
    groupAnimation.animations = @[animation1, animation2]; 
    groupAnimation.duration = 4.0;
    //add the animation to the color layer
    [colorLayer addAnimation:groupAnimation forKey:nil];
}

animation-2

4.过渡
(1).淡入淡出切换图片

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@interface ViewController ()

@property (nonatomic, weak) IBOutlet UIImageView *imageView;
@property (nonatomic, copy) NSArray *images;

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    //set up images
    self.images = @[[UIImage imageNamed:@"Anchor.png"],
                    [UIImage imageNamed:@"Cone.png"],
                    [UIImage imageNamed:@"Igloo.png"],
                    [UIImage imageNamed:@"Spaceship.png"]];
}

- (IBAction)switchImage
{
    //set up crossfade transition
    CATransition *transition = [CATransition animation];
    transition.type = kCATransitionFade;
    //apply transition to imageview backing layer
    [self.imageView.layer addAnimation:transition forKey:nil];
    //cycle to next image
    UIImage *currentImage = self.imageView.image;
    NSUInteger index = [self.images indexOfObject:currentImage];
    index = (index + 1) % [self.images count];
    self.imageView.image = self.images[index];
}

@end

(2).UITabBarController切换动画

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#import "AppDelegate.h"
#import "FirstViewController.h" 
#import "SecondViewController.h"
#import <QuartzCore/QuartzCore.h>
@implementation AppDelegate
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    self.window = [[UIWindow alloc] initWithFrame: [[UIScreen mainScreen] bounds]];
    UIViewController *viewController1 = [[FirstViewController alloc] init];
    UIViewController *viewController2 = [[SecondViewController alloc] init];
    self.tabBarController = [[UITabBarController alloc] init];
    self.tabBarController.viewControllers = @[viewController1, viewController2];
    self.tabBarController.delegate = self;
    self.window.rootViewController = self.tabBarController;
    [self.window makeKeyAndVisible];
    return YES;
}
- (void)tabBarController:(UITabBarController *)tabBarController didSelectViewController:(UIViewController *)viewController
{
    //set up crossfade transition
    CATransition *transition = [CATransition animation];
    transition.type = kCATransitionFade;
    //apply transition to tab bar controller's view
    [self.tabBarController.view.layer addAnimation:transition forKey:nil];
}
@end

5.使用UIView +transitionFromView:toView:duration:options:completion:和+transitionWithView:duration:options:animations:做过渡

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@interface ViewController ()
@property (nonatomic, weak) IBOutlet UIImageView *imageView;
@property (nonatomic, copy) NSArray *images;
@end
@implementation ViewController
- (void)viewDidLoad
{
    [super viewDidLoad]; //set up images
    self.images = @[[UIImage imageNamed:@"Anchor.png"],
                    [UIImage imageNamed:@"Cone.png"],
                    [UIImage imageNamed:@"Igloo.png"],
                    [UIImage imageNamed:@"Spaceship.png"]];
- (IBAction)switchImage
{
    [UIView transitionWithView:self.imageView duration:1.0
                       options:UIViewAnimationOptionTransitionFlipFromLeft
                    animations:^{
                        //cycle to next image
                        UIImage *currentImage = self.imageView.image;
                        NSUInteger index = [self.images indexOfObject:currentImage];
                        index = (index + 1) % [self.images count];
                        self.imageView.image = self.images[index];
                    }
                    completion:NULL];
}

@end

6.使用renderInContext:自定义过渡
对原来view进行截图得到coverView,给coverView加上缩小、旋转、变透明动画，同时改变原来view的backgroundColor。动画完成后，移除coverView。

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@implementation ViewController
- (IBAction)performTransition
{
    //preserve the current view snapshot
    UIGraphicsBeginImageContextWithOptions(self.view.bounds.size, YES, 0.0);
    [self.view.layer renderInContext:UIGraphicsGetCurrentContext()];
    UIImage *coverImage = UIGraphicsGetImageFromCurrentImageContext();
    //insert snapshot view in front of this one
    UIView *coverView = [[UIImageView alloc] initWithImage:coverImage];
    coverView.frame = self.view.bounds;
    [self.view addSubview:coverView];
    //update the view (we'll simply randomize the layer background color)
    CGFloat red = arc4random() / (CGFloat)INT_MAX;
    CGFloat green = arc4random() / (CGFloat)INT_MAX;
    CGFloat blue = arc4random() / (CGFloat)INT_MAX;
    self.view.backgroundColor = [UIColor colorWithRed:red green:green blue:blue alpha:1.0];
    //perform animation (anything you like)
    [UIView animateWithDuration:1.0 animations:^{
        //scale, rotate and fade the view
        CGAffineTransform transform = CGAffineTransformMakeScale(0.01, 0.01);
        transform = CGAffineTransformRotate(transform, M_PI_2);
        coverView.transform = transform;
        coverView.alpha = 0.0;
    } completion:^(BOOL finished) {
        //remove the cover view now we're finished with it
        [coverView removeFromSuperview];
    }];
}
@end

7.移除正在运行动画
有两种方法：

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- (void)removeAnimationForKey:(NSString *)key;

or

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- (void)removeAllAnimations;

example：有start和stop两个按钮，start开始动画，stop停止动画

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@interface ViewController ()

@property (nonatomic, weak) IBOutlet UIView *containerView;
@property (nonatomic, strong) CALayer *shipLayer;

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    //add the ship
    self.shipLayer = [CALayer layer];
    self.shipLayer.frame = CGRectMake(0, 0, 128, 128);
    self.shipLayer.position = CGPointMake(150, 150);
    self.shipLayer.contents = (__bridge id)[UIImage imageNamed: @"Ship.png"].CGImage;
    [self.containerView.layer addSublayer:self.shipLayer];
}

- (IBAction)start
{
    //animate the ship rotation
    CABasicAnimation *animation = [CABasicAnimation animation];
    animation.keyPath = @"transform.rotation";
    animation.duration = 2.0;
    animation.byValue = @(M_PI * 2);
    animation.delegate = self;
    [self.shipLayer addAnimation:animation forKey:@"rotateAnimation"];
}

- (IBAction)stop
{
    [self.shipLayer removeAnimationForKey:@"rotateAnimation"];
}

- (void)animationDidStop:(CAAnimation *)anim finished:(BOOL)flag
{
    //log that the animation stopped
    NSLog(@"The animation stopped (finished: %@)", flag? @"YES": @"NO");
}

@end

总结

  • 隐式动画：Core Animation支持CALayer一些可动画属性（Animatable Properties）自动执行动画，我们只需要改变属性值，系统自动完成动画。UIView.layer获得的layer默认隐式动画是禁用的的。
  • 显示动画：自定义来指定动画，主要可以通过：CABasicAnimation、CAKeyFrameAnimation、CAAnimationGroup、CATransition等类来做动画