Cocos2d-x之Touch事件

游戏跟视频最大的区别就是互动，玩家可以操控游戏中的角色，现在的移动设备几乎人手一台，基本上全部都是基于触屏操作的，今天就来学习一下cocos2d-x是怎么实现对触屏操作的处理的。
1.首先来了解一下相关的几个类、处理触屏事件时操作和执行的流程
CCTouch：它封装了触摸点，可以通过locationInView函数返回一个CCPoint。
CCTouchDelegate：它是触摸事件委托，就是系统捕捉到触摸事件后交由它或者它的子类处理，所以我们在处理触屏事件时，必须得继承它。它封装了下面这些处理触屏事件的函数：

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virtualvoidccTouchesBegan(CCSet *pTouches, CCEvent *pEvent); virtualvoidccTouchesMoved(CCSet *pTouches, CCEvent *pEvent); virtualvoidccTouchesEnded(CCSet *pTouches, CCEvent *pEvent); virtualvoidccTouchesCancelled(CCSet *pTouches, CCEvent *pEvent);   virtualboolccTouchBegan(CCTouch *pTouch, CCEvent *pEvent); virtualvoidccTouchMoved(CCTouch *pTouch, CCEvent *pEvent); virtualvoidccTouchEnded(CCTouch *pTouch, CCEvent *pEvent); virtualvoidccTouchCancelled(CCTouch *pTouch, CCEvent *pEvent);

ccTouchesCancelled和ccTouchCancelled函数很少用，在接到系统中断通知，需要取消触摸事件的时候才会调用此方法。如：应用长时间无响应、当前view从window上移除、触摸的时候来电话了等。

CCTargetedTouchDelegate和CCStandardTouchDelegate是CCTouchDelegate的子类，类结构图如下：

CCStandardTouchDelegate用于处理多点触摸;CCTargetedTouchDelegate用于处理单点触摸。

CCTouchDispatcher：实现触摸事件分发，它封装了下面这两个函数，可以把CCStandardTouchDelegate和CCTargetedTouchDelegate添加到分发列表中：

1 2	voidaddStandardDelegate(CCTouchDelegate *pDelegate, intnPriority); voidaddTargetedDelegate(CCTouchDelegate *pDelegate, intnPriority,boolbSwallowsTouches);

CCTouchHandler：封装了CCTouchDelegate和其对应的优先级，优先级越高，分发的时候越容易获得事件处理权，CCStandardTouchHandler和CCTargetedTouchHandler是它的子类。

下面分析一下触屏事件处理和执行流程：
用户自定义类继承CCTouchDelegate，重写触屏事件处理函数和registerWithTouchDispatcher函数，在init或者onEnter函数中调用registerWithTouchDispatcher函数，如：

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voidGameLayer::registerWithTouchDispatcher() {     cocos2d::CCTouchDispatcher::sharedDispatcher()->addTargetedDelegate(this, 0, true); }

把相应的CCTouchDelegate添加到CCTouchDispatcher的分发列表中。addTargetedDelegate函数会创建CCTouchDelegate对应的CCTouchHandler对象并添加到CCMutableArraym_pTargetedHandlers中，看源码：

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voidCCTouchDispatcher::addTargetedDelegate(CCTouchDelegate *pDelegate, intnPriority,boolbSwallowsTouches) {       CCTouchHandler *pHandler = CCTargetedTouchHandler::handlerWithDelegate(pDelegate, nPriority, bSwallowsTouches);     if(! m_bLocked)     {         forceAddHandler(pHandler, m_pTargetedHandlers);     }     else     {         /**....*/     } }   voidCCTouchDispatcher::forceAddHandler(CCTouchHandler *pHandler, CCMutableArray *pArray) {     unsignedintu = 0;       CCMutableArray::CCMutableArrayIterator iter;     for(iter = pArray->begin(); iter != pArray->end(); ++iter)     {         CCTouchHandler *h = *iter;          if(h)          {             if(h->getPriority() < pHandler->getPriority())             {                 ++u;             }               if(h->getDelegate() == pHandler->getDelegate())             {                 CCAssert(0,"");                 return;             }          }     }       pArray->insertObjectAtIndex(pHandler, u); }

注意forceAddHandler函数中，pHandler是被添加的对象：pHandler->getPriority()的值越小u的值就越小，因此插入到目标容器中的位置也就越靠前，说明优先级的值越小优先级反而越高,也就能先响应事件（CCMenu的默认值是-128）。 前面事件分发时就是从m_pTargetedHandlers中取出CCXXXTouchHandler，然后调用handler对应的delegate的：pHandler->getDelegate()->ccTouchBegan(pTouch, pEvent);，执行的是CCTouchDispatcher的touches函数，考虑到篇幅问题，就不贴出具体代码了。该函数首先会先处理targeted 再处理standard，所以CCTargetedTouchDelegate比CCStandardTouchDelegate优先级高。那什么时候触发执行touches函数呢？CCTouchDispatcher继承了EGLTouchDelegate类，EGLTouchDelegate类源码:

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classCC_DLL EGLTouchDelegate { public:     virtualvoidtouchesBegan(CCSet* touches, CCEvent* pEvent) = 0;     virtualvoidtouchesMoved(CCSet* touches, CCEvent* pEvent) = 0;     virtualvoidtouchesEnded(CCSet* touches, CCEvent* pEvent) = 0;     virtualvoidtouchesCancelled(CCSet* touches, CCEvent* pEvent) = 0;       virtual~EGLTouchDelegate() {} };

CCTouchDispatcher中实现了这四个函数，正是在这四个函数中调用了touches函数：

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voidCCTouchDispatcher::touchesBegan(CCSet *touches, CCEvent *pEvent) {     if(m_bDispatchEvents)     {         this->touches(touches, pEvent, CCTOUCHBEGAN);     } } /**其他三个方法类似 **/

这几个触屏处理函数是由具体平台底层调用的，在AppDelegate.cpp中有这段代码:

1 2	CCDirector *pDirector = CCDirector::sharedDirector(); pDirector->setOpenGLView(&CCEGLView::sharedOpenGLView());

继续跟进setOpenGLView函数，发现了这段代码：

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CCTouchDispatcher *pTouchDispatcher = CCTouchDispatcher::sharedDispatcher(); m_pobOpenGLView->setTouchDelegate(pTouchDispatcher); pTouchDispatcher->setDispatchEvents(true);

调用了具体平台下的CCEGLView类中的setTouchDelegate函数。由于我是在windows平台下，所以CCEGLView此时对应CCEGLView_win32.h文件的CCEGLView类，对应的setTouchDelegate函数为：

1	void   setTouchDelegate(EGLTouchDelegate * pDelegate);

系统最终通过CCEGLView类的WindowProc函数处理鼠标在Windows窗口的DOWN、MOVE、UP事件，通过pDelegate分别调用touchesBegan、touchesMoved、touchesEnded函数。

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LRESULTCCEGLView::WindowProc(UINTmessage,WPARAMwParam,LPARAMlParam) {     switch(message)     {     caseWM_LBUTTONDOWN:         if(m_pDelegate && m_pTouch && MK_LBUTTON == wParam)         {             POINT pt = {(short)LOWORD(lParam), (short)HIWORD(lParam)};             if(PtInRect(&m_rcViewPort, pt))             {                 m_bCaptured = true;                 SetCapture(m_hWnd);                 m_pTouch->SetTouchInfo(0, (float)(pt.x - m_rcViewPort.left) / m_fScreenScaleFactor,                     (float)(pt.y - m_rcViewPort.top) / m_fScreenScaleFactor);                 m_pSet->addObject(m_pTouch);                 m_pDelegate->touchesBegan(m_pSet, NULL);             }         }         break;       caseWM_MOUSEMOVE:         if(MK_LBUTTON == wParam && m_bCaptured)         {             m_pTouch->SetTouchInfo(0, (float)((short)LOWORD(lParam)- m_rcViewPort.left) / m_fScreenScaleFactor,                 (float)((short)HIWORD(lParam) - m_rcViewPort.top) / m_fScreenScaleFactor);             m_pDelegate->touchesMoved(m_pSet, NULL);         }         break;       caseWM_LBUTTONUP:         if(m_bCaptured)         {             m_pTouch->SetTouchInfo(0, (float)((short)LOWORD(lParam)- m_rcViewPort.left) / m_fScreenScaleFactor,                 (float)((short)HIWORD(lParam) - m_rcViewPort.top) / m_fScreenScaleFactor);             m_pDelegate->touchesEnded(m_pSet, NULL);             m_pSet->removeObject(m_pTouch);             ReleaseCapture();             m_bCaptured = false;         }         break; /** .... */ } }

ok，现在应该明白了触屏操作相关函数的执行过程了，在其他平台下应该类似。

2. 实现触屏事件处理
知道了原理之后，实现起来就很简单了：定义一个CCTouchDelegate(或者其子类CCTargetedTouchDelegate/CCStandardTouchDelegate)，然后重写那几个处理函数(began、move、end)，并把定义好的CCTouchDelegate添加到分发列表中，在onExit函数中实现从分发列表中删除。
在平常的开发中，一般有两种方式：(1)继承CCLayer,在层中处理触屏函数。(2)继承CCSprite和CCTouchDelegate(或者其子类)。
上面两种方式，从原理上来说是一样的。
1. 下面是采用继承CCLayer的方式处理触屏事件。
(1)CCStandardTouchDelegate
添加CCStandardTouchDelegate是非常简单的，只需要重写触屏处理函数和调用setIsTouchEnabled(true)。主要代码如下：

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//init函数中 this->setIsTouchEnabled(true);   voidGameLayer::ccTouchesBegan(CCSet* pTouches,CCEvent* pEvent) {     CCSetIterator it = pTouches->begin();     CCTouch* touch = (CCTouch*)(*it);     CCpoint touchLocation = touch->locationInView( touch->view() );     touchLocation = CCDirector::sharedDirector()->convertToGL(m_tBeginPos);         /** .... **/ }

这里为什么没有把CCStandardTouchDelegate添加进分发列表和从分发列表删除的操作呢，因为setIsTouchEnabled函数已经帮我们做了，看源码：

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voidCCLayer::setIsTouchEnabled(boolenabled) {     if(m_bIsTouchEnabled != enabled)     {         m_bIsTouchEnabled = enabled;         if(m_bIsRunning)         {             if(enabled)             {                 this->registerWithTouchDispatcher();             }             else             {                 // have problems?                 CCTouchDispatcher::sharedDispatcher()->removeDelegate(this);             }         }     } }   voidCCLayer::registerWithTouchDispatcher() {     /** .... **/     CCTouchDispatcher::sharedDispatcher()->addStandardDelegate(this,0); }   voidCCLayer::onExit() {     if( m_bIsTouchEnabled )     {         CCTouchDispatcher::sharedDispatcher()->removeDelegate(this);         unregisterScriptTouchHandler();     }       CCNode::onExit(); }

(2) CCTargetedTouchDelegate
直接看cocos2d-x中的CCMenu(菜单)类，它是继承CCLayer的。部分源码如下：

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classCC_DLL CCMenu : publicCCLayer,publicCCRGBAProtocol     {         /** .... */         virtualvoidregisterWithTouchDispatcher();           /**         @brief For phone event handle functions         */         virtualboolccTouchBegan(CCTouch* touch, CCEvent* event);         virtualvoidccTouchEnded(CCTouch* touch, CCEvent* event);         virtualvoidccTouchCancelled(CCTouch *touch, CCEvent* event);         virtualvoidccTouchMoved(CCTouch* touch, CCEvent* event);           /**         @since v0.99.5         override onExit         */         virtualvoidonExit();           /** .... */     }; }   //Menu - Events,在CCLayer的onEnter中被调用     voidCCMenu::registerWithTouchDispatcher()     {         CCTouchDispatcher::sharedDispatcher()->addTargetedDelegate(this, kCCMenuTouchPriority, true);     }       boolCCMenu::ccTouchBegan(CCTouch* touch, CCEvent* event)     {         /** .... */         }    voidCCMenu::onExit()     {          /** .... */         CCLayer::onExit();     }

2.下面实现继承CCSprite的方式
定义一个Ball类继承CCSprite和CCTargetedTouchDelegate。源码如下：

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classBall : publicCCSprite,publicCCTargetedTouchDelegate { public:     Ball(void);     virtual~Ball(void);       virtualvoidonEnter();     virtualvoidonExit();       virtualboolccTouchBegan(CCTouch* touch, CCEvent* event);     virtualvoidccTouchMoved(CCTouch* touch, CCEvent* event);     virtualvoidccTouchEnded(CCTouch* touch, CCEvent* event); /** .... */   };   voidBall::onEnter() {     CCTouchDispatcher::sharedDispatcher()->addTargetedDelegate(this, 0, true);     CCSprite::onEnter(); }   voidBall::onExit() {     CCTouchDispatcher::sharedDispatcher()->removeDelegate(this);     CCSprite::onExit(); }   boolBall::ccTouchBegan(CCTouch* touch, CCEvent* event) {     CCPoint touchPoint = touch->locationInView( touch->view() );     touchPoint = CCDirector::sharedDirector()->convertToGL( touchPoint );    /** .... */     returntrue; }

注意：virtual bool ccTouchBegan(CCTouch *pTouch, CCEvent *pEvent)的返回值对触屏消息是有影响的。
如果返回false，表示不处理ccTouchMoved()，ccTouchEnded()，ccTouchCanceld()方法，而交由后面接收触屏消息的对象处理；如果返回true，表示会处理ccTouchMoved()，ccTouchEnded()，ccTouchCanceld()方法。请看CCTouchDispatcher.cpp的touches函数部分源码，它是用来分发事件的：

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boolbClaimed = false; if(uIndex == CCTOUCHBEGAN) {     bClaimed = pHandler->getDelegate()->ccTouchBegan(pTouch, pEvent);     //返回true     if(bClaimed)     {         pHandler->getClaimedTouches()->addObject(pTouch);     } }else if(pHandler->getClaimedTouches()->containsObject(pTouch)) {     // moved ended canceled     bClaimed = true;       switch(sHelper.m_type)     {     caseCCTOUCHMOVED:         pHandler->getDelegate()->ccTouchMoved(pTouch, pEvent);         break;     caseCCTOUCHENDED:         pHandler->getDelegate()->ccTouchEnded(pTouch, pEvent);         pHandler->getClaimedTouches()->removeObject(pTouch);         break;     caseCCTOUCHCANCELLED:         pHandler->getDelegate()->ccTouchCancelled(pTouch, pEvent);         pHandler->getClaimedTouches()->removeObject(pTouch);         break;     } }

如果返回true，并且addTargetedDelegate(CCTouchDelegate *pDelegate, int nPriority, bool bSwallowsTouches)，bSwallowsTouches为true，则表示消耗掉此触屏消息，后面需要接收触屏消息的对象就接收不到触屏消息了。

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if(bClaimed && pHandler->isSwallowsTouches())                {                    if(bNeedsMutableSet)                    {                        pMutableTouches->removeObject(pTouch);                    }                      break;                }

把该触摸对象CCTouch从数组pMutableTouches中移除了，并且跳出当前for循环，而CCStandardTouchHandler需要从pMutableTouches取出触摸对象进行处理的，这样后面的CCTargetedTouchHandler和CCStandardTouchHandler就都处理不了。

http://blog.youkuaiyun.com/zyxhjy/article/details/8126301