Cocos2d-x 中的多点触控陷阱，和实现移动和缩放

<span style="white-space:pre">	</span><span style="font-size:24px;color:#ff0000;">在1年前左右，我需要利用cocos2d-x做一个类似地图的东西。当然就需要到平移和缩放了，在很多游戏中如果能够实现缩放效果，那可以提升游戏的一个格逼！最近我又需要做类似的工作，但是我先前就删掉了那份代码，再次的上当让我觉得有必要我的发现分享给大家。</span>

<span style="font-size:24px;color:#ff0000;"><span style="white-space:pre">	</span>首先是一个手指控制平移，两个手指控制缩放（注意是按层的锚点，在我这里就是屏幕中心），旋转的话可以看情况绕锚点旋转，如果锚点不在屏幕中心那就相当别扭。所以我的这个触摸层的坐标是固定的，平移改变的其实是锚点位置，这点很重要，我觉得也很合理方便。同样我提醒一句，变旋转边平移产生的效果不是很炫酷，反而是让人头晕。我还发现写代码头晕不是因为代码，而是因为自己做的粗糙图片和垃圾特效（包括滥用粒子效果）。</span>

<span style="font-size:24px;color:#ff0000;"><span style="white-space:pre">	</span>好，回到正题。首先MapLayer.h是这样的，就是触摸层。</span>

#ifndef __MAP_LAYER_H__
#define __MAP_LAYER_H__

#include "cocos2d.h"

USING_NS_CC;

class Map : public cocos2d::CCLayer
{
public:

	float map_x,map_y,map_w,map_h;

	CCPoint pos_position_pre;

	CCPoint pos_scale_pre[2];

	int  touchs_num;
 	bool two_release_one;
	float scale;

    virtual bool init();  

	void ccTouchesBegan(CCSet *pTouches,CCEvent *pEvent);
	void ccTouchesMoved(CCSet *pTouches,CCEvent *pEvent);
    void ccTouchesEnded(CCSet *pTouches,CCEvent *pEvent);
	void update(float dt);
	void draw();
    // implement the "static node()" method manually
    CREATE_FUNC(Map);
};

首先，我们需要touchs_num记录实际当前按着的手指数量。因为pTouchs->count()返回的根本不是人们所想得值。Began里的值是有新手指按下就会产生1，而且它只会返回1，即便是两个手指同时按下，实际上两个手指不可能同时按下，就好比比划一个V字再慢慢的插自己的眼睛总有一个眼睛先有感觉。而程序60帧每秒，那速度就更快了。所以在began里面写：

void Map::ccTouchesBegan(CCSet *pTouches,CCEvent *pEvent)
{
	if(pTouches->count() == 1)
	{
		if(touchs_num == 0  )
		{
			CCTouch* touch = dynamic_cast<CCTouch*> (pTouches->anyObject());
			CCPoint position = touch->getLocationInView();
			position = CCDirector::sharedDirector()->convertToGL(position);
<span style="white-space:pre">			</span>//这里处理一个按键操作的相关初始化
		}
		else if(touchs_num == 1  )
		{
			CCTouch* touch = dynamic_cast<CCTouch*> (pTouches->anyObject());
			CCPoint position = touch->getLocationInView();
			position = CCDirector::sharedDirector()->convertToGL(position);

			//这里处理两个按键操作的相关初始化

}

touchs_num++;

}

}

每传入一次事件，touchs_num就加1，不用多说。相应的在Ended里需要减1，因为它和began一样，每次都只能穿一个坐标进来。我想说的是这种设计真的很坑爹。反正我在安卓上测试至少是这种效果。

<span style="font-family: Arial,Helvetica,sans-serif;">void Map::ccTouchesEnded(CCSet *pTouches,CCEvent *pEvent)</span>

{

	if(pTouches->count() == 1 )
	{
		CCTouch* touch = dynamic_cast<CCTouch*> (pTouches->anyObject());
		CCPoint position = touch->getLocationInView();
		position = CCDirector::sharedDirector()->convertToGL(position);
		if(touchs_num == 1)
		{
			two_release_one = 0;
			
		}
		else if(touchs_num == 2)
		{
			two_release_one = 1;
			scale = this->getScale();
		}
	
		CCLog("touchend\n");

		touchs_num--;

	}
}

仔细看上面，其中有一个布尔变量叫two_release_one，意思是否两个手指移开了一个手指。因为仅靠touhs_num无法分辨是点击了一个手指还是两个手指移开了一个的情况。核心的处理就在Moved，我推荐利用两次调用的变量差值实现动态效果，所以类还需要几个变量存储上一次的属性值，比如

<span style="white-space:pre">	</span>CCPoint pos_position_pre;//移动前的点坐标

<span style="white-space:pre">	</span>CCPoint pos_scale_pre[2];//缩放前的两点坐标

<span style="white-space:pre">	</span>float scale;//缩放前的值

<span style="font-size:18px;color:#ff0000;">还有一个问题是层开启了 锚点对位置的不影响。所以需要这样初始化：</span><span style="font-size: 24px; white-space: pre;">	</span>

<span style="font-family: Arial,sans-serif;"><span style="font-size:10px;">this->setTouchEnabled(true);</span></span>

<span style="font-family: Arial,sans-serif;"><span style="font-size:10px;">this->ignoreAnchorPointForPosition(false);//开启锚点对坐标的影响</span></span>

<span style="font-family: Arial,sans-serif;"><span style="font-size:10px;">this->setContentSize(CCSize(map_w,map_h));//设置层大小</span></span>

<span style="font-family: Arial,sans-serif;"><span style="font-size:10px;">this->setAnchorPoint(ccp(0.5,0.5));</span></span>

<span style="white-space: pre;">	</span><span style="font-size:18px;color:#ff0000;">一个手指平移效果，需要在began中的if(touchs_num==0)中记录下pos_position_pre。</span>

<span style="font-size:18px;color:#ff0000;"><span style="white-space: pre;">	</span>两个手指缩放效果，要在began的if(touchs_num==0)<span style="font-family: Arial,sans-serif;">和</span><span style="font-family: Arial,sans-serif; background-color: rgb(255,255);">if(t...==1)中分记录下两点的坐标。这样才能计算出两个按下手指之间的距离，再说一遍，began中一次只能接收一个点。</span></span>

<span style="font-size:18px;color:#ff0000;">然后在moved的if(touchs_num == 1 && !two_release_one)中实现平移：</span>

<span style="font-family: Arial,sans-serif;">
</span>

<span style="white-space: pre;">	</span>CCPoint pos_dt = position - pos_position_pre;//计算差值

<span style="font-family: Arial,sans-serif;">//差值除以层的大小[setContentSize设置的]，再除以/scale[可以不除，效果不同</span>

this->setAnchorPoint(this->getAnchorPoint()-ccp(pos_dt.x/map_w,pos_dt.y/map_h)/scale);
pos_position_pre=position;//替换前值

<span style="font-family: Arial,sans-serif;">
</span>

<span style="font-family: Arial,sans-serif;"><span style="font-size:18px;color:#ff0000;">上面的条件!two_release去掉的话会和两点操作产生冲突，会出bug，就是这样bug很烦出理，如果有兴趣可以研究，我就不再费力说了。</span></span>

<span style="font-family: Arial,sans-serif;">在moved的else if(pTouches->count() == 2 && two_release_one ==0)中出理缩放：</span>

<span style="font-family: Arial,sans-serif;">CCPoint temp_pre=pos_scale_pre[0]-pos_scale_pre[1];//向量，为了后面求两点距离</span>

CCPoint temp_now=positions[0]-positions[1];
this->setScale(scale*temp_now.getLength()/temp_pre.getLength());

<span style="font-family: Arial,sans-serif;"><span style="font-size:18px;color:#ff0000;">它和平移不同的是在ended里面替换前值。</span></span>

if(touchs_num == 1)
{
<span style="white-space:pre">	</span>two_release_one = 0;
}
else if(touchs_num == 2)
{
<span style="white-space:pre">	</span>two_release_one = 1;
<span style="white-space:pre">	</span>scale = this->getScale();
}

<span style="font-family: Arial,sans-serif;"><span style="font-size:18px;color:#ff0000;">大概就如此了，最后给出完整的源文件，可以结合头文件研究研究，总体按照这个方式可以正确的平移和缩放，如果想要实现旋转就更方便了，应为它的锚点就在屏幕中心。</span></span>

#include "MapLayer.h"

USING_NS_CC;


const int MAP_START_W	=	512;
const int MAP_START_H	=	512;
const int MAP_START_X	=	1280/2;
const int MAP_START_Y	=	210+512/2;

// on "init" you need to initialize your instance
bool Map::init()
{
 	scale=1.0;
 	two_release_one=0;
	touchs_num =0;
	map_x = MAP_START_X;
	map_y = MAP_START_Y;
	map_h = MAP_START_H;
	map_w = MAP_START_W;
    //////////////////////////////
    // 1. super init first
    if ( !CCLayer::init() )
    {
        return false;
    }
    
	this->scheduleUpdate();//开启update函数
	this->setTouchEnabled(true);
	this->ignoreAnchorPointForPosition(false);//开启锚点

    CCSize visibleSize = CCDirector::sharedDirector()->getVisibleSize();
    CCPoint origin = CCDirector::sharedDirector()->getVisibleOrigin(); //Origin 起源

	this->setContentSize(CCSize(map_w,map_h));
	this->setAnchorPoint(ccp(0.5,0.5));
	this->setPosition(ccp(map_x,map_y));
    
	CCSprite* spr_tower_arrow = CCSprite::create("resource/image/tower_arrow.png");
	spr_tower_arrow->setPosition(ccp(0,0));
	this->addChild(spr_tower_arrow,1);

    return true;
}

void Map::draw()
{
	glLineWidth(2.0);
	ccDrawColor4B(255,255);
	
		ccDrawLine(ccp(0,0),ccp(0,MAP_START_H));
		ccDrawLine(ccp(0,ccp(MAP_START_W,0));
		ccDrawLine(ccp(0,MAP_START_H),MAP_START_W));
		ccDrawLine(ccp(MAP_START_W,MAP_START_W));
		
}

void Map::update(float dt)
{
	
	CCLog("%f,%f,%f",this->getScale(),this->getAnchorPoint().x,this->getAnchorPoint().y);
}

void Map::ccTouchesBegan(CCSet *pTouches,CCEvent *pEvent)
{
	if(pTouches->count() == 1)
	{
		if(touchs_num == 0  )
		{
			CCTouch* touch = dynamic_cast<CCTouch*> (pTouches->anyObject());
			CCPoint position = touch->getLocationInView();
			position = CCDirector::sharedDirector()->convertToGL(position);

			pos_position_pre=position;

			//////////////////////////////////////////////////////////////////////////
			pos_scale_pre[0] = position;
		}
		else if(touchs_num == 1  )
		{
			CCTouch* touch = dynamic_cast<CCTouch*> (pTouches->anyObject());
			CCPoint position = touch->getLocationInView();
			position = CCDirector::sharedDirector()->convertToGL(position);

			pos_scale_pre[1] = position;
		}

		
		touchs_num++;
	}
	
}

void Map::ccTouchesMoved(CCSet *pTouches,CCEvent *pEvent)
{
	if(pTouches->count() == 1)
	{
		if(touchs_num == 1  && !two_release_one)
		{
			CCTouch* touch = dynamic_cast<CCTouch*> (pTouches->anyObject());
			CCPoint position = touch->getLocationInView();
			position = CCDirector::sharedDirector()->convertToGL(position);

			CCPoint pos_dt = position - pos_position_pre;
			

			this->setAnchorPoint(this->getAnchorPoint()-ccp(pos_dt.x/map_w,pos_dt.y/map_h)/scale);

			pos_position_pre=position;

		}
		
		
		
		CCLog("touchmove\n");
	}
	else if(pTouches->count() == 2 && two_release_one ==0)
	{
		CCPoint positions[2];
		int i=0;
		for(CCSetIterator it = pTouches->begin() ; it != pTouches->end();it++,i++)
		{
			CCTouch* touch = dynamic_cast<CCTouch*>(*it);
			CCPoint position = touch->getLocationInView();
			positions[i] = CCDirector::sharedDirector()->convertToGL(position);
		}

		CCPoint temp_pre=pos_scale_pre[0]-pos_scale_pre[1];
		CCPoint temp_now=positions[0]-positions[1];

	
		this->setScale(scale*temp_now.getLength()/temp_pre.getLength());


	}
}

void Map::ccTouchesEnded(CCSet *pTouches,CCEvent *pEvent)
{

	if(pTouches->count() == 1 )
	{
		CCTouch* touch = dynamic_cast<CCTouch*> (pTouches->anyObject());
		CCPoint position = touch->getLocationInView();
		position = CCDirector::sharedDirector()->convertToGL(position);
		if(touchs_num == 1)
		{
			two_release_one = 0;
			
		}
		else if(touchs_num == 2)
		{
			two_release_one = 1;
			scale = this->getScale();
		}
	
		CCLog("touchend\n");

		touchs_num--;

	}
}