Cocos2dx------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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virtual void ccTouchesBegan(CCSet *pTouches, CCEvent *pEvent);
virtual void ccTouchesMoved(CCSet *pTouches, CCEvent *pEvent);
virtual void ccTouchesEnded(CCSet *pTouches, CCEvent *pEvent);
virtual void ccTouchesCancelled(CCSet *pTouches, CCEvent *pEvent);
 
virtual bool ccTouchBegan(CCTouch *pTouch, CCEvent *pEvent);
virtual void ccTouchMoved(CCTouch *pTouch, CCEvent *pEvent);
virtual void ccTouchEnded(CCTouch *pTouch, CCEvent *pEvent);
virtual void ccTouchCancelled(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。

CCTargetedTouchDelegateCCStandardTouchDelegate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:

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void addStandardDelegate(CCTouchDelegate *pDelegate, int nPriority);
void addTargetedDelegate(CCTouchDelegate *pDelegate, int nPriority, bool bSwallowsTouches);

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,CCStandardTouchHandlerCCTargetedTouchHandler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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void GameLayer::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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void CCTouchDispatcher::addTargetedDelegate(CCTouchDelegate *pDelegate, int nPriority, bool bSwallowsTouches)
{  
     CCTouchHandler *pHandler = CCTargetedTouchHandler::handlerWithDelegate(pDelegate, nPriority, bSwallowsTouches);
     if (! m_bLocked)
     {
         forceAddHandler(pHandler, m_pTargetedHandlers);
     }
     else
     {
         /**....*/
     }
}
 
void CCTouchDispatcher::forceAddHandler(CCTouchHandler *pHandler, CCMutableArray *pArray)
{
     unsigned int u = 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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class CC_DLL EGLTouchDelegate
{
public :
     virtual void touchesBegan(CCSet* touches, CCEvent* pEvent) = 0;
     virtual void touchesMoved(CCSet* touches, CCEvent* pEvent) = 0;
     virtual void touchesEnded(CCSet* touches, CCEvent* pEvent) = 0;
     virtual void touchesCancelled(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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void CCTouchDispatcher::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:

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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:

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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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LRESULT CCEGLView::WindowProc( UINT message, WPARAM wParam, LPARAM lParam)
{
     switch (message)
     {
     case WM_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 ;
 
     case WM_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 ;
 
     case WM_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 );
 
void GameLayer::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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void CCLayer::setIsTouchEnabled( bool enabled)
{
     if (m_bIsTouchEnabled != enabled)
     {
         m_bIsTouchEnabled = enabled;
         if (m_bIsRunning)
         {
             if (enabled)
             {
                 this ->registerWithTouchDispatcher();
             }
             else
             {
                 // have problems?
                 CCTouchDispatcher::sharedDispatcher()->removeDelegate( this );
             }
         }
     }
}
 
void CCLayer::registerWithTouchDispatcher()
{
     /** .... **/
     CCTouchDispatcher::sharedDispatcher()->addStandardDelegate( this ,0);
}
 
void CCLayer::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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class CC_DLL CCMenu : public CCLayer, public CCRGBAProtocol
     {
         /** .... */
         virtual void registerWithTouchDispatcher();
 
         /**
         @brief For phone event handle functions
         */
         virtual bool ccTouchBegan(CCTouch* touch, CCEvent* event);
         virtual void ccTouchEnded(CCTouch* touch, CCEvent* event);
         virtual void ccTouchCancelled(CCTouch *touch, CCEvent* event);
         virtual void ccTouchMoved(CCTouch* touch, CCEvent* event);
 
         /**
         @since v0.99.5
         override onExit
         */
         virtual void onExit();
 
         /** .... */
     };
}
 
//Menu - Events,在CCLayer的onEnter中被调用
     void CCMenu::registerWithTouchDispatcher()
     {
         CCTouchDispatcher::sharedDispatcher()->addTargetedDelegate( this , kCCMenuTouchPriority, true );
     }
 
     bool CCMenu::ccTouchBegan(CCTouch* touch, CCEvent* event)
     {
         /** .... */
         }
 
  void CCMenu::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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class Ball : public CCSprite, public CCTargetedTouchDelegate
{
public :
     Ball( void );
     virtual ~Ball( void );
 
     virtual void onEnter();
     virtual void onExit();
 
     virtual bool ccTouchBegan(CCTouch* touch, CCEvent* event);
     virtual void ccTouchMoved(CCTouch* touch, CCEvent* event);
     virtual void ccTouchEnded(CCTouch* touch, CCEvent* event);
/** .... */
 
};
 
void Ball::onEnter()
{
     CCTouchDispatcher::sharedDispatcher()->addTargetedDelegate( this , 0, true );
     CCSprite::onEnter();
}
 
void Ball::onExit()
{
     CCTouchDispatcher::sharedDispatcher()->removeDelegate( this );
     CCSprite::onExit();
}
 
bool Ball::ccTouchBegan(CCTouch* touch, CCEvent* event)
{
     CCPoint touchPoint = touch->locationInView( touch->view() );
     touchPoint = CCDirector::sharedDirector()->convertToGL( touchPoint );   
/** .... */
     return true ;
}

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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bool bClaimed = 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)
     {
     case CCTOUCHMOVED:
         pHandler->getDelegate()->ccTouchMoved(pTouch, pEvent);
         break ;
     case CCTOUCHENDED:
         pHandler->getDelegate()->ccTouchEnded(pTouch, pEvent);
         pHandler->getClaimedTouches()->removeObject(pTouch);
         break ;
     case CCTOUCHCANCELLED:
         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.csdn.net/zyxhjy/article/details/8126301

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