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1、创建全局定时器，bool CCDirector::init(void)函数中，调用

// scheduler    m_pScheduler = new CCScheduler();

2、在每帧渲染前，都会调用CCScheduler的update方法// Draw the Scenevoid CCDirector::drawScene(void){    // calculate "global" dt    calculateDeltaTime();    //tick before glClear: issue #533    if (! m_bPaused) //调用定时器的update方法    {        m_pScheduler->update(m_fDeltaTime);    }}

3、CCScheduler中有几个很重要的成员变量，	//每帧都要调用的定时器    struct _listEntry *m_pUpdatesNegList;        // list of priority < 0 //存放priority < 0的Update，优先级最高    struct _listEntry *m_pUpdates0List;            // list priority == 0 //存放priority == 0的Update    struct _listEntry *m_pUpdatesPosList;        // list priority > 0	//存放priority > 0的Update，优先级最低    //方便快速查找    struct _hashUpdateEntry *m_pHashForUpdates; // hash used to fetch quickly the list entries for pause,delete,etc    // Used for "selectors with interval"，设置了时间间隔的定时器列表    struct _hashSelectorEntry *m_pHashForTimers; //

CCScheduler的update函数很大，主要是几个循环。

// main loopvoid CCScheduler::update(float dt){    m_bUpdateHashLocked = true;    if (m_fTimeScale != 1.0f)    {        dt *= m_fTimeScale;    }    // Iterate over all the Updates' selectors    tListEntry *pEntry, *pTmp;    // updates with priority < 0 优先调用    // pEntry->target->update(dt) 调用target的update方法，例继承与CCNode的类    //可以重写  CCNode的 update方法    /*      * Update method will be called automatically every frame if "scheduleUpdate" is called, and the node is "live"     */    //virtual void update(float delta);    DL_FOREACH_SAFE(m_pUpdatesNegList, pEntry, pTmp)    {        if ((! pEntry->paused) && (! pEntry->markedForDeletion))        {            pEntry->target->update(dt);         }    }    // updates with priority == 0    DL_FOREACH_SAFE(m_pUpdates0List, pEntry, pTmp)    {        if ((! pEntry->paused) && (! pEntry->markedForDeletion))        {            pEntry->target->update(dt);        }    }    // updates with priority > 0    DL_FOREACH_SAFE(m_pUpdatesPosList, pEntry, pTmp)    {        if ((! pEntry->paused) && (! pEntry->markedForDeletion))        {            pEntry->target->update(dt);        }    }    // Iterate over all the custom selectors    //遍历有时间间隔的定时器列表，调用相应的方法    for (tHashTimerEntry *elt = m_pHashForTimers; elt != NULL; )    {        m_pCurrentTarget = elt;        m_bCurrentTargetSalvaged = false;        if (! m_pCurrentTarget->paused)        {            // The 'timers' array may change while inside this loop            for (elt->timerIndex = 0; elt->timerIndex < elt->timers->num; ++(elt->timerIndex))            {                elt->currentTimer = (CCTimer*)(elt->timers->arr[elt->timerIndex]);                elt->currentTimerSalvaged = false;                elt->currentTimer->update(dt);                if (elt->currentTimerSalvaged)                {                    // The currentTimer told the remove itself. To prevent the timer from                    // accidentally deallocating itself before finishing its step, we retained                    // it. Now that step is done, it's safe to release it.                    elt->currentTimer->release();                }                elt->currentTimer = NULL;            }        }        // elt, at this moment, is still valid        // so it is safe to ask this here (issue #490)        elt = (tHashTimerEntry *)elt->hh.next;        // only delete currentTarget if no actions were scheduled during the cycle (issue #481)        if (m_bCurrentTargetSalvaged && m_pCurrentTarget->timers->num == 0)        {            removeHashElement(m_pCurrentTarget);        }    }    // Iterate over all the script callbacks    //遍历针对脚本的定时器列表    if (m_pScriptHandlerEntries)    {        for (int i = m_pScriptHandlerEntries->count() - 1; i >= 0; i--)        {            CCSchedulerScriptHandlerEntry* pEntry = static_cast
   
    (m_pScriptHandlerEntries->objectAtIndex(i));            if (pEntry->isMarkedForDeletion())            {                m_pScriptHandlerEntries->removeObjectAtIndex(i);            }            else if (!pEntry->isPaused())            {                pEntry->getTimer()->update(dt);            }        }    }    // delete all updates that are marked for deletion    // updates with priority < 0    //删除一些没用定时器    DL_FOREACH_SAFE(m_pUpdatesNegList, pEntry, pTmp)    {        if (pEntry->markedForDeletion)        {            this->removeUpdateFromHash(pEntry);        }    }    // updates with priority == 0    DL_FOREACH_SAFE(m_pUpdates0List, pEntry, pTmp)    {        if (pEntry->markedForDeletion)        {            this->removeUpdateFromHash(pEntry);        }    }    // updates with priority > 0    DL_FOREACH_SAFE(m_pUpdatesPosList, pEntry, pTmp)    {        if (pEntry->markedForDeletion)        {            this->removeUpdateFromHash(pEntry);        }    }    m_bUpdateHashLocked = false;    m_pCurrentTarget = NULL;}
   

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