cocos2dx学习笔记：自定义动作实现圆周运动

最近在翻帖子的时候发现很多大牛都自己实现自定义动作，而不是通过各种动作进行组合，正好最近需要一个圆周运动的效果，就自己写了一个自定义的动作，这里备注下大致的实现思路。

备注：

该动作并未实际应用在游戏中，可能有bug。

数学复习：

截图来自【 http://202.113.29.3/nankaisource/mathhands/Elementary%20mathematics/0103/010301/01030101.htm 】

实现方式：

可参考这篇文章来实现：【 http://blog.csdn.net/u012945598/article/details/17605409 】 

作者自己也写了一个功能增强版的圆周运动，可以实现螺旋线式的圆周运动。代码比较简单，就不在细说了。

自己的实现：

CircleMoveAct.h：

#ifndef __CIRCLE_MOVE_ACT_H__
#define __CIRCLE_MOVE_ACT_H__

#include "cocos2d.h"
//http://202.113.29.3/nankaisource/mathhands/Elementary%20mathematics/0103/010301/01030101.htm

class CircleMoveAct : public cocos2d::CCActionInterval
{
public:
	bool initWithDuration(float duration, const cocos2d::CCPoint& center, float scaleDiff, float angle);
    
	virtual cocos2d::CCObject* copyWithZone(cocos2d::CCZone* pZone);
    virtual void startWithTarget(cocos2d::CCNode *pTarget);
    virtual void update(float time);
public:
    static CircleMoveAct* create(float duration, const cocos2d::CCPoint& center, float scale, float angle);

protected:

	float m_duration;
	cocos2d::CCPoint m_center;
	float m_scaleDiff;
	float m_currScale;
	float m_angle;	
	float m_anglePreFrame;
	int m_frameCnts;
	cocos2d::CCPoint m_initPos;
};

#endif // __CIRCLE_MOVE_ACT_H__

CircleMoveAct.cpp：

#include "CircleMoveAct.h"
USING_NS_CC;


CircleMoveAct* CircleMoveAct::create(float duration, const CCPoint& center, float scale, float angle)
{
	CircleMoveAct *pRet = new CircleMoveAct();
	pRet->initWithDuration(duration, center, scale, angle);
	pRet->autorelease();

	return pRet;
}

bool CircleMoveAct::initWithDuration(float duration, const CCPoint& center, float scaleDiff, float angle)
{
	if (CCActionInterval::initWithDuration(duration))
	{
		this->m_duration = duration;
		this->m_center = center;
		this->m_scaleDiff = scaleDiff;
		this->m_currScale = 1.0f;
		this->m_angle = angle;

		/************************************************************************/
		/* 计算每次update调用时需要转动的弧度                                   */
		/************************************************************************/
		this->m_anglePreFrame = angle / duration * CCDirector::sharedDirector()->getAnimationInterval() / (180 / M_PI);
		this->m_frameCnts = 0;
		return true;
	}
	return false;
}

CCObject* CircleMoveAct::copyWithZone(CCZone *pZone)
{
	CCZone* pNewZone = NULL;
	CircleMoveAct* pCopy = NULL;
	if(pZone && pZone->m_pCopyObject) 
	{
		pCopy = (CircleMoveAct*)(pZone->m_pCopyObject);
	}
	else
	{
		pCopy = new CircleMoveAct();
		pZone = pNewZone = new CCZone(pCopy);
	}

	CCActionInterval::copyWithZone(pZone);
	pCopy->initWithDuration(m_duration, m_center, m_scaleDiff, m_angle);

	CC_SAFE_DELETE(pNewZone);
	return pCopy;
}

void CircleMoveAct::startWithTarget(CCNode *pTarget)
{
	CCActionInterval::startWithTarget(pTarget);
	m_initPos = pTarget->getPosition();
}
void CircleMoveAct::update(float time)
{
	m_frameCnts++;
	m_currScale += m_scaleDiff;

	CCPoint newPos = ccpRotateByAngle(m_initPos, m_center, m_frameCnts * m_anglePreFrame);
	CCPoint diff = ccpSub(newPos, m_center);
	newPos = diff * m_currScale + m_center;
	
	m_pTarget->setPosition(newPos);


//debug
#if 0
	CCDrawNode *node = CCDrawNode::create();
	node->drawDot(newPos,3,ccc4f(128,128,128,128));
	m_pTarget->getParent()->addChild(node);
#endif

}

正常调用方式：

	CCSize size = CCDirector::sharedDirector()->getVisibleSize();
	CCSprite *test = CCSprite::create("CloseNormal.png");
	test->setPosition(ccp(size.width/2 + 20, size.height/2));//设置起点
	test->setAnchorPoint(ccp(0.5,0.5));
	//设置用时，圆心，是否缩放(不缩放设置为0.0f)，旋转角度
	CircleMoveAct *act = CircleMoveAct::create(10,ccp(size.width/2, size.height/2), 0.0f,1500);
	test->runAction(act);
	this->addChild(test);

 截图如下：

缩放调用方式：

	CCSize size = CCDirector::sharedDirector()->getVisibleSize();
	CCSprite *test = CCSprite::create("CloseNormal.png");
	test->setPosition(ccp(size.width/2 + 20, size.height/2));//设置起点
	test->setAnchorPoint(ccp(0.5,0.5));
	//设置用时，圆心，缩放递增值0.01f，旋转角度
	CircleMoveAct *act = CircleMoveAct::create(10,ccp(size.width/2, size.height/2), 0.01f,1500);
	test->runAction(act);
	this->addChild(test);

截图如下：