CAAnimation动画的一些知识点

分隐式动画和显式动画

CAAnimatione采用了CAMediaTiming协议,可以调整时间,包括持续时间,速度,重复次数;采用了CAAction协议,可以通过响应动作的方式来显示动画.

CAAnimation的一些派生类:

CATransition 提供渐变效果:(推拉push效果,消退fade效果,揭开reveal效果)

CAAnimationGroup 允许多个动画同时播放

CABasicAnimation 提供了对单一动画的实现

CAKeyframeAnimation 关键桢动画,可以定义行动路线

CAConstraint 约束类,在布局 器类中用它来设置属性

CAConstraintLayoutManager 约束布局管理器,是用来将多个CALayer进行布局的.各个CALayer是通过名称来区分,而布局属性是通过CAConstraint来设置的.

CATransaction 事务类,可以对多个layer的属性同时进行修改.它分隐式事务,和显式事务.

事务管理(Transactions)

事务分两种:

1.隐式事务(implicit transaction)

除显式事务外,任何对于CALayer属性的修改,都是隐式事务.这样的事务会在run-loop中被提交.

如:

theLayer.opacity = 0.0;

theLayer.zPosition = -200;

theLayer.position = CGPointMake(0.0, 0.0);

2.显式事务(explicit transaction)

a. 通过明确的调用begin,commit来提交动画.优点是可以同时修改多个Layer的属性.

如:

[CATransaction begin];

[CATransaction setValue:(id)kCFBooleanTrue

                               forKey:kCATransactionDisableActions];

[aLayer removeFromSuperlayer];

[CATransaction commit];

b.可以重置持续时间

可以在begin,commit对中临时修改动画持续时间.

[CATransaction begin]

[CATransaction setValue:[NSNumber numberWithFloat:10.0f]

                               forKey:kCATransactionAnimationDuration];

theLayer.zPosition = 200.0;

theLayer.opacity = 0.0;

[CATransaction commit];

c.事务可以嵌套.

如:

//第一层嵌套

[CATransaction begin];

[CATransaction setValue:[NSNumber numberWithFloat:2.0f]

                             forKey:kCATransactionAnimationDuration];

theLayer.position = CGPointMake(0.0, 0.0);

//第二层嵌套

[CATransaction begin];

[CATransaction setValue:[NSNumber numberWithFloat:5.0f]

                               forKey:kCATransactionAnimationDuration];

theLayer.zPosition = 200.0;

theLayer.opacity = 0.0;

[CATransaction commit];

[CATransaction commit];

布局管理器示例如下:

//创建和设置一个布局管理器

theLayer.layoutManager = [CAConstraintLayoutManager layoutManager];

//创建layerA

CALayer *layerA = [CALayer layer];

layerA.name = @"layerA";

//设置layerA的中点位置等于超类的中点位置

[layerA addConstraint:[CAConstraint constraintWithAttribute:kCAConstraintMidY

                                                                                       relativeTo:@"superLayer"

                                                                                       attribute:kCAConstraintMidY]];

[layerA addConstraint:[CAConstraint constraintWithAttribute:kCAConstraintMidX

                                                                                       relativeTo:@"superLayer"

                                                                                       attribute:kCAConstraintMidX]];

[theLayer addSublayer:layerA];

//创建layerB

CALayer *layerB = [CALayer layer];

layerB.name = @"layerB";

//设置layerB的宽度等于layerA的宽度

[layerA addConstraint:[CAConstraint constraintWithAttribute:kCAConstraintWidth

                                                                                       relativeTo:@"LayerA"

                                                                                       attribute:kCAConstraintWidth]];

[layerA addConstraint:[CAConstraint constraintWithAttribute:kCAConstraintMidX

                                                                                       relativeTo:@"layerA"

                                                                                       attribute:kCAConstraintMidX]];

[theLayer addSublayer:layerB];