基本动作和组合动作实现了针对精灵的各种运动和动画效果的改变。但这样的改变速度匀速的、线性的。通过ActionEase及其的派生类和Speed 类我们可以使精灵以非匀速或非线性速度运动，这样看起了效果更加逼真。
ActionEase的类图如下图所示。
下面我们通过一个实例介绍一下这些动作中速度的控制的使用，这个实例如下图所示，上图是一个操作菜单场景，选择菜单可以进入到下图动作场景，在下图动作场景中点击Go按钮可以执行我们选择的动作效果，点击Back按钮可以返回到菜单场景。
下面我们再看看具体的程序代码，首先看一下看HelloWorldScene.h文件，它的代码如下：
[html] view plaincopy
- #ifndef __HELLOWORLD_SCENE_H__
- #define __HELLOWORLD_SCENE_H__
- #include "cocos2d.h"
- #include "MyActionScene.h"
- typedef enum ①
- {
- kEaseIn = 1
- ,kEaseOut
- ,kEaseInOut
- ,kEaseSineIn
- ,kEaseSineOut
- ,kEaseSineInOut
- ,kEaseExponentialIn
- ,kEaseExponentialOut
- ,kEaseExponentialInOut
- ,kSpeed
- } ActionTypes; ②
- class HelloWorld : public cocos2d:
ayer - {
- public:
- static cocos2d::Scene* createScene();
- virtual bool init();
- void OnClickMenu(cocos2d::Ref* pSender);
- CREATE_FUNC(HelloWorld);
- };
- #endif // __HELLOWORLD_SCENE_H__
上述代码第①~②是定义个枚举类型ActionTypes，枚举类型ActionTypes中定义了10个常量，这10个常量对应10个菜单项。
HelloWorldScene的实现代码HelloWorldScene.ccp文件，它的主要代码如下：
[html] view plaincopy
- bool HelloWorld::init()
- {
- if( !Layer::init() )
- {
- returnfalse;
- }
- SizevisibleSize = Director::getInstance()->getVisibleSize();
- Pointorigin = Director::getInstance()->getVisibleOrigin();
- autobg = Sprite::create("background.png");
- bg->setPosition(Point(visibleSize.width/2,visibleSize.height /2));
- this->addChild(bg);
- autopItmLabel1 = Label::createWithBMFont("fonts/fnt2.fnt","EaseIn");
- autopItmMenu1 = MenuItemLabel::create(pItmLabel1,
- CC_CALLBACK_1(HelloWorld::OnClickMenu, this));
- pItmMenu1->setTag(kEaseIn);
- autopItmLabel2 = Label::createWithBMFont("fonts/fnt2.fnt","EaseOut");
- autopItmMenu2 = MenuItemLabel::create(pItmLabel2,
- CC_CALLBACK_1(HelloWorld::OnClickMenu,this));
- pItmMenu2->setTag(kEaseOut);
- autopItmLabel3 = Label::createWithBMFont("fonts/fnt2.fnt","EaseInOut");
- autopItmMenu3 = MenuItemLabel::create(pItmLabel3,
- CC_CALLBACK_1(HelloWorld::OnClickMenu,this));
- pItmMenu3->setTag(kEaseInOut);
- autopItmLabel4 = Label::createWithBMFont("fonts/fnt2.fnt","EaseSineIn");
- autopItmMenu4 = MenuItemLabel::create(pItmLabel4,
- CC_CALLBACK_1(HelloWorld::OnClickMenu,this));
- pItmMenu4->setTag(kEaseSineIn);
- autopItmLabel5 = Label::createWithBMFont("fonts/fnt2.fnt", "EaseSineOut");
- autopItmMenu5 = MenuItemLabel::create(pItmLabel5,
- CC_CALLBACK_1(HelloWorld::OnClickMenu,this));
- pItmMenu5->setTag(kEaseSineOut);
- autopItmLabel6 = Label::createWithBMFont("fonts/fnt2.fnt","EaseSineInOut");
- autopItmMenu6 = MenuItemSprite::create(pItmLabel6,
- CC_CALLBACK_1(HelloWorld::OnClickMenu,this));
- pItmMenu6->setTag(kEaseSineInOut);
- autopItmLabel7 = Label::createWithBMFont("fonts/fnt2.fnt","EaseExponentialIn");
- autopItmMenu7 = MenuItemSprite::create(pItmLabel7,
- CC_CALLBACK_1(HelloWorld::OnClickMenu,this));
- pItmMenu7->setTag(kEaseExponentialIn);
- autopItmLabel8 = Label::createWithBMFont("fonts/fnt2.fnt","EaseExponentialOut");
- autopItmMenu8 = MenuItemLabel::create(pItmLabel8,
- CC_CALLBACK_1(HelloWorld::OnClickMenu,this));
- pItmMenu8->setTag(kEaseExponentialOut);
- autopItmLabel9 = Label::createWithBMFont("fonts/fnt2.fnt","EaseExponentialInOut");
- autopItmMenu9 = MenuItemLabel::create(pItmLabel9,
- CC_CALLBACK_1(HelloWorld::OnClickMenu,this));
- pItmMenu9->setTag(kEaseExponentialInOut);
- autopItmLabel10 = Label::createWithBMFont("fonts/fnt2.fnt","Speed");
- autopItmMenu10 = MenuItemLabel::create(pItmLabel10,
- CC_CALLBACK_1(HelloWorld::OnClickMenu,this));
- pItmMenu10->setTag(kSpeed);
- automn = Menu::create(pItmMenu1,pItmMenu2,pItmMenu3,pItmMenu4,pItmMenu5,
- pItmMenu6,pItmMenu7,pItmMenu8,pItmMenu9,pItmMenu10,NULL);
- mn->alignItemsInColumns(2,2, 2, 2, 2, NULL);
- this->addChild(mn);
- returntrue;
- }
- void HelloWorld::OnClickMenu(Ref* pSender)
- {
- MenuItem*nmitem = (MenuItem*)pSender;
- auto sc = Scene::create();
- auto layer = MyAction::create();
- layer->setTag(nmitem->getTag());
- sc->addChild(layer);
- autoreScene = TransitionSlideInR::create(1.0f, sc);
- Director::getInstance()->replaceScene(reScene);
- }
在上诉代码大家比较熟悉了，我们这里就不再介绍了。下面我们再看看下一个场景MyActionScene，它的MyActionScene.ccp，它的主要代码如下：
[html] view plaincopy
- void MyAction::goMenu(Ref* pSender)
- {
- log("Tag = %i",this->getTag());
- FiniteTimeAction * ac1 = (FiniteTimeAction *)MoveBy::create(2,Point(200, 0));
- FiniteTimeAction * ac2 = ((FiniteTimeAction *)ac1)->reverse();
- ActionInterval * ac = Sequence::create(ac1, ac2, NULL);
- switch (this->getTag()) {
- case kEaseIn:
- sprite->runAction(EaseIn::create(ac, 3)); ①
- break;
- case kEaseOut:
- sprite->runAction(EaseOut::create(ac, 3)); ②
- break;
- case kEaseInOut:
- sprite->runAction(EaseInOut::create(ac,3)); ③
- break;
- case kEaseSineIn:
- sprite->runAction(EaseSineIn::create(ac)); ④
- break;
- case kEaseSineOut:
- sprite->runAction(EaseSineOut::create(ac)); ⑤
- break;
- case kEaseSineInOut:
- sprite->runAction(EaseSineInOut::create(ac)); ⑥
- break;
- case kEaseExponentialIn:
- sprite->runAction(EaseExponentialIn::create(ac)); ⑦
- break;
- case kEaseExponentialOut:
- sprite->runAction(EaseExponentialOut::create(ac)); ⑧
- break;
- case kEaseExponentialInOut:
- sprite->runAction(EaseExponentialInOut::create(ac)); ⑨
- break;
- case kSpeed:
- sprite->runAction(Speed::create(ac, (CCRANDOM_0_1() * 5))); ⑩
- break;
- }
- }
第①行代码sprite->runAction(EaseIn::create(ac, 3))是以3倍速度由慢至快。第②代码sprite->runAction(EaseOut::create(ac, 3))是以3倍速度由快至慢。第③代码sprite->runAction(EaseInOut::create(ac, 3))是以3倍速度由慢至快再由快至慢。
第④代码sprite->runAction(EaseSineIn::create(ac))是采用正弦变换速度由慢至快。第⑤代码sprite->runAction(EaseSineOut::create(ac))是采用正弦变换速度由快至慢。第⑥代码sprite->runAction(EaseOut::create(ac, 3)) 是采用正弦变换速度由慢至快再由快至慢。
第⑦代码sprite->runAction(EaseExponentialIn::create(ac))采用指数变换速度由慢至快。第⑧代码sprite->runAction(EaseExponentialOut::create(ac))采用指数变换速度由快至慢。第⑨代码sprite->runAction(EaseExponentialInOut::create(ac)) 采用指数变换速度由慢至快再由快至慢。
第⑩代码sprite->runAction(Speed::create(ac, (CCRANDOM_0_1() * 5))) 随机设置变换速度。
更多内容请关注Cocos2d-x系列图书《Cocos2d-x实战（卷Ⅰ）：C++开发》
本书交流讨论网站：http://www.cocoagame.net
欢迎加入cocos2d-x技术讨论群：257760386、327403678