一、前言

• 每一个UIView内部都默认关联着一个CALayer对象，我们可用称这个Layer为Root Layer（根层）
• 所有的非RootLayer根层，也就是手动创建的CALayer对象，都存在着隐式动画

二、什么是隐式动画？

• 当对非RootLayer的部分属性进行修改时，默认会自动产生一些动画效果
• 而这些属性称为AnimatableProperties(可动画属性)
• 也就是说，对非根层的layer可动画属性进行修改产生的动画，就称为隐式动画

三、可动画属性 Animatable Properties

• 如上所述：我们可以修改可动画属性，来进行隐式动画，现在介绍可动画属性

• 查看CALayer头文件：查看部分可动画属性

• 哪些才可以称着，可动画属性呢？ -> 属性，注释中包含 Animatable的

• 常见可动画属性

  • bounds：用于设置CALayer的宽度和高度。修改这个属性会产生缩放动画
  • backgroundColor：用于设置CALayer的背景色。修改这个属性会产生背景色的渐变动画
  • position：用于设置CALayer的位置。修改这个属性会产生平移动画
  • ............

// 查看部分头文件，还有其他的可动画属性不在此

/* The bounds of the layer. Defaults to CGRectZero. Animatable. */
@property CGRect bounds;

/* The position in the superlayer that the anchor point of the layer's
 * bounds rect is aligned to. Defaults to the zero point. Animatable. */
@property CGPoint position;

/* The Z component of the layer's position in its superlayer. Defaults
 * to zero. Animatable. */
@property CGFloat zPosition;

/* Defines the anchor point of the layer's bounds rect, as a point in
 * normalized layer coordinates - '(0, 0)' is the bottom left corner of
 * the bounds rect, '(1, 1)' is the top right corner. Defaults to
 * '(0.5, 0.5)', i.e. the center of the bounds rect. Animatable. */
@property CGPoint anchorPoint;

/* The Z component of the layer's anchor point (i.e. reference point for
 * position and transform). Defaults to zero. Animatable. */
@property CGFloat anchorPointZ;

/* A transform applied to the layer relative to the anchor point of its
 * bounds rect. Defaults to the identity transform. Animatable. */
@property CATransform3D transform;

/* Convenience methods for accessing the `transform' property as an
 * affine transform. */
- (CGAffineTransform)affineTransform;
- (void)setAffineTransform:(CGAffineTransform)m;

/* Unlike NSView, each Layer in the hierarchy has an implicit frame
 * rectangle, a function of the `position', `bounds', `anchorPoint',
 * and `transform' properties. When setting the frame the `position'
 * and `bounds.size' are changed to match the given frame. */
@property CGRect frame;

/* When true the layer and its sublayers are not displayed. Defaults to
 * NO. Animatable. */
@property(getter=isHidden) BOOL hidden;

四 隐式动画 实现 : CATransaction(动画事务)

• 可以通过动画事务(CATransaction)关闭默认的隐式动画效果

[CATransactionbegin];
[CATransactionsetDisableActions:YES];
self.myview.layer.position= CGPointMake(10,10);
[CATransactioncommit];

五、实例

• 实例：

  
  隐式动画.gif
  • 点击屏幕，让控制器上的view视图上的一个矩形子控件，不断地进行改变：位置，颜色，与圆角

• 思路：其实很简单，在touchBegin:方法中 -> 就是不断修改layer的可动画属性实现的

• 代码实现：如下

#import "ViewController.h"

@interface ViewController ()

@property (nonatomic, weak) CALayer *greenLayer;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    // 添加 一个自定义的layer到控制器的view的layer上
    CALayer *layer = [CALayer layer];
    
    _greenLayer = layer;
    
    layer.position = CGPointMake(0, 0);
    layer.bounds = CGRectMake(0, 0, 100, 100);
    layer.anchorPoint = CGPointMake(0, 0);
    layer.backgroundColor = [UIColor greenColor].CGColor;
    
    [self.view.layer addSublayer:layer];
}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    // 开启事务
    [CATransaction begin];
    
    
//    [CATransaction setDisableActions:YES];
//    [CATransaction setAnimationDuration:2];
    _greenLayer.position = CGPointMake(arc4random_uniform(250), arc4random_uniform(300));
    
    _greenLayer.backgroundColor = [self randomColor].CGColor;
    _greenLayer.cornerRadius = arc4random_uniform(50);
    
    _greenLayer.borderColor = [self randomColor].CGColor;
    _greenLayer.borderWidth = arc4random_uniform(5);
    
    // 提交事务
    [CATransaction commit];
    
}

/**
 *  返回 随机色
 */
- (UIColor *)randomColor
{
    CGFloat r = arc4random_uniform(256) / 255.0;
    CGFloat g = arc4random_uniform(256) / 255.0;
    CGFloat b = arc4random_uniform(256) / 255.0;
    return [UIColor colorWithRed:r green:g blue:b alpha:1];
}

@end
     ```