• 每一个UIView都默认关联着一个CALayer，我们成这个layer为root layer
• 所有的非root layer都存在默认的隐式动画，隐式动画默认为1/4秒。

iOS开发中的动画分为两种:

• 一种为UIView动画,又称隐式动画,动画后frame的数值发生了变化。
• 另一种是CALayer动画,又称显示动画,动画后模型层的数据不会发生变化,图形回到原来的位置。

但是在实际开发中,因为UIView可以响应用户交互,所以UIView动画用的多.

一个小小的demo：

• 点击屏幕改变颜色 XXChangeColorViewController
• 点击屏幕改变颜色运用转场动画实现 XXCustomChangeColorViewController
• 点击屏幕改变颜色，以及跟随触摸点改变位置 XXChangeColorAndFrameViewController

三个重要控制器源代码如下
XXChangeColorViewController

#import "XXChangeColorViewController.h"

#define XXRamdomColor [UIColor colorWithRed:arc4random_uniform(255)/255.0 green:arc4random_uniform(255)/255.0 blue:arc4random_uniform(255)/255.0 alpha:1]

@interface XXChangeColorViewController ()

//显示颜色的layer
@property (nonatomic, strong) CALayer *colorLayer;

//colorView
@property (nonatomic, strong) UIView *colorView;

@end

@implementation XXChangeColorViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    self.title = @"点击屏幕改变颜色";
    
    //用layer实现
    self.colorLayer = [CALayer layer];
    self.colorLayer.frame = CGRectMake(100, 100, 100, 100);
    self.colorLayer.backgroundColor = [UIColor redColor].CGColor;
    [self.view.layer addSublayer:self.colorLayer];
    
    //用view实现
    UIView *colorView = [[UIView alloc] init];
    self.colorView = colorView;
    colorView.frame = CGRectMake(100, 300, 100, 100);
    colorView.backgroundColor = [UIColor redColor];
    [self.view addSubview:colorView];
}
- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
    self.colorLayer.backgroundColor = XXRamdomColor.CGColor;
    self.colorView.backgroundColor = XXRamdomColor;
}



@end

XXCustomChangeColorViewController

#import "XXCustomChangeColorViewController.h"
#define XXRamdomColor [UIColor colorWithRed:arc4random_uniform(255)/255.0 green:arc4random_uniform(255)/255.0 blue:arc4random_uniform(255)/255.0 alpha:1]

@interface XXCustomChangeColorViewController ()

//colorLayer
@property (nonatomic, strong) CALayer *colorLayer;

@end

@implementation XXCustomChangeColorViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    self.title = @"自定义改变颜色";
    
    //用layer实现
    self.colorLayer = [CALayer layer];
    self.colorLayer.frame = CGRectMake(100, 100, 100, 100);
    self.colorLayer.backgroundColor = [UIColor redColor].CGColor;
    [self.view.layer addSublayer:self.colorLayer];
    
    //加入转场动画
    CATransition *transition = [CATransition animation];
    transition.type = kCATransitionPush;
    transition.subtype = kCATransitionFromLeft;
    self.colorLayer.actions = @{@"backgroundColor": transition};
}

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
    self.colorLayer.backgroundColor = XXRamdomColor.CGColor;
}

@end

XXChangeColorAndFrameViewController

#import "XXChangeColorAndFrameViewController.h"


#define XXRamdomColor [UIColor colorWithRed:arc4random_uniform(255)/255.0 green:arc4random_uniform(255)/255.0 blue:arc4random_uniform(255)/255.0 alpha:1]

@interface XXChangeColorAndFrameViewController ()

//colorLayer
@property (nonatomic, strong) CALayer *colorLayer;

@end

@implementation XXChangeColorAndFrameViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    self.title = @"改变颜色以及跟随手势改变位置";
    
    //用layer实现
    self.colorLayer = [CALayer layer];
    self.colorLayer.frame = CGRectMake(100, 100, 100, 100);
    self.colorLayer.backgroundColor = [UIColor redColor].CGColor;
    [self.view.layer addSublayer:self.colorLayer];  
}

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
    //获取到当前的触摸点
    CGPoint point = [[touches anyObject] locationInView:self.view];
    //如果触摸点在colorLayer范围内，则改变颜色，否则跟随手指改变位置
    if ([self.colorLayer.presentationLayer hitTest:point]) {
        self.colorLayer.backgroundColor = XXRamdomColor.CGColor;
    }else {
        [CATransaction begin];
        [CATransaction setAnimationDuration:4.0];
        self.colorLayer.position = point;
        [CATransaction commit];
    }
}

@end

效果如下图

P9w9CArdI9S0hkAVHNyfnPrRjdTBKV5Y.gif