Cocos2d-x如何控制动作速度

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：

#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::Layer
{
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：

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：

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。