//透明动画。
    CABasicAnimation * animation = [CABasicAnimation animationWithKeyPath:@"opacity"];

　　　　

      animation.beginTime = CACurrentMediaTime()+3;//开始时间

    animation.fromValue = @1.0;//开始值。
    animation.toValue = @0.1;//结束值 
    animation.duration = 2.0f;//时长
    animation.fillMode = kCAFillModeBackwards;//填充模式
    self.myLabel.layer addAnimation:animation forKey:@"opacity" ];

/* The begin time of the object, in relation to its parent object, if
 * applicable. Defaults to 0. */

@property CFTimeInterval beginTime;
从什么时候开始执行动画。
/* The basic duration of the object. Defaults to 0. */
//动画时长
@property CFTimeInterval duration;

/* The rate of the layer. Used to scale parent time to local time, e.g.
 * if rate is 2, local time progresses twice as fast as parent time.
 * Defaults to 1. */
//执行时，相对速度。
@property float speed;

/* Additional offset in active local time. i.e. to convert from parent
 * time tp to active local time t: t = (tp - begin) * speed + offset.
 * One use of this is to "pause" a layer by setting `speed‘ to zero and
 * `offset‘ to a suitable value. Defaults to 0. */

@property CFTimeInterval timeOffset;

/* The repeat count of the object. May be fractional. Defaults to 0. */

@property float repeatCount;//重复次数

/* The repeat duration of the object. Defaults to 0. */

@property CFTimeInterval repeatDuration;//多入后重播。

/* When true, the object plays backwards after playing forwards. Defaults
 * to NO. */

@property BOOL autoreverses;//自动反向播放

/* Defines how the timed object behaves outside its active duration.
 * Local time may be clamped to either end of the active duration, or
 * the element may be removed from the presentation. The legal values
 * are `backwards‘, `forwards‘, `both‘ and `removed‘. Defaults to
 * `removed‘. */

@property(copy) CAMediaTimingFillMode fillMode;//填充模式

@end

/* `fillMode‘ options. */

CA_EXTERN CAMediaTimingFillMode const kCAFillModeForwards//执行填充。动画结束在哪儿就在哪儿。必须是不移除动画。
    API_AVAILABLE(macos(10.5), ios(2.0), watchos(2.0), tvos(9.0));
CA_EXTERN CAMediaTimingFillMode const kCAFillModeBackwards//执行前就填充到相应位置或状态。
    API_AVAILABLE(macos(10.5), ios(2.0), watchos(2.0), tvos(9.0));
CA_EXTERN CAMediaTimingFillMode const kCAFillModeBoth
    API_AVAILABLE(macos(10.5), ios(2.0), watchos(2.0), tvos(9.0));
CA_EXTERN CAMediaTimingFillMode const kCAFillModeRemoved
    API_AVAILABLE(macos(10.5), ios(2.0), watchos(2.0), tvos(9.0));

基本和android 一样一样的。