本文共 3929 字，大约阅读时间需要 13 分钟。

1、分析下update类型，即每帧都调用的定时器，如何实现：

//CCScheduler中的成员变量struct _listEntry *m_pUpdates0List;            // list priority == 0-->>存放update类型定时器的结构// A list double-linked list used for "updates with priority"typedef struct _listEntry{    struct _listEntry   *prev, *next;    CCObject            *target;        // not retained (retained by hashUpdateEntry)    int                 priority;    bool                paused;    bool                markedForDeletion; // selector will no longer be called and entry will be removed at end of the next tick} tListEntry;

2、添加update类型的定时器    /** Schedules the 'update' selector for a given target with a given priority.     The 'update' selector will be called every frame.     The lower the priority, the earlier it is called.     @since v0.99.3     @lua NA     */    void scheduleUpdateForTarget(CCObject *pTarget, int nPriority, bool bPaused);    -->>    void CCScheduler::scheduleUpdateForTarget(CCObject *pTarget, int nPriority, bool bPaused){    //先判断是否已经加入    tHashUpdateEntry *pHashElement = NULL;    HASH_FIND_INT(m_pHashForUpdates, &pTarget, pHashElement);    if (pHashElement)    {#if COCOS2D_DEBUG >= 1        CCAssert(pHashElement->entry->markedForDeletion,"");#endif        // TODO: check if priority has changed!        pHashElement->entry->paused = bPaused;        pHashElement->entry->markedForDeletion = false;        return;    }    //根据优先级加入到不同的链表中    // most of the updates are going to be 0, that's way there    // is an special list for updates with priority 0    if (nPriority == 0)    {        appendIn(&m_pUpdates0List, pTarget, bPaused);    }    else if (nPriority < 0)    {        priorityIn(&m_pUpdatesNegList, pTarget, nPriority, bPaused);    }    else    {        // priority > 0        priorityIn(&m_pUpdatesPosList, pTarget, nPriority, bPaused);    }}-->>分析下appendIn(&m_pUpdates0List, pTarget, bPaused)这个，其他连个类似，只不过加入了优先级的概念，需要根据优先级确定插入位置，但是都为加入到快速查找哈希链表中，而且同样会retain。void CCScheduler::appendIn(_listEntry **ppList, CCObject *pTarget, bool bPaused){    //分配tListEntry    tListEntry *pListElement = (tListEntry *)malloc(sizeof(*pListElement));    pListElement->target = pTarget;    pListElement->paused = bPaused;    pListElement->markedForDeletion = false;    //添加进列表    DL_APPEND(*ppList, pListElement);        //添加到快速查找哈希链表中    // update hash entry for quicker access    tHashUpdateEntry *pHashElement = (tHashUpdateEntry *)calloc(sizeof(*pHashElement), 1);    pHashElement->target = pTarget;    pTarget->retain();  //有一次retain对象的操作，会影响对象的释放    pHashElement->list = ppList;    pHashElement->entry = pListElement;    HASH_ADD_INT(m_pHashForUpdates, target, pHashElement);}3、移除update类型的定时器   /** Unschedules the update selector for a given target     @since v0.99.3     @lua NA     */    void unscheduleUpdateForTarget(const CCObject *pTarget);    -->>    void CCScheduler::unscheduleUpdateForTarget(const CCObject *pTarget){    if (pTarget == NULL)    {        return;    }    //如果哈希表中有    tHashUpdateEntry *pElement = NULL;    HASH_FIND_INT(m_pHashForUpdates, &pTarget, pElement);    if (pElement)    {        if (m_bUpdateHashLocked)        {            pElement->entry->markedForDeletion = true; //标记为移除        }        else        {            this->removeUpdateFromHash(pElement->entry);//真正的移除        }    }}-->>void CCScheduler::removeUpdateFromHash(struct _listEntry *entry){    tHashUpdateEntry *element = NULL;    HASH_FIND_INT(m_pHashForUpdates, &entry->target, element);    if (element)    {        // list entry，从链表移除        DL_DELETE(*element->list, element->entry);        free(element->entry);        // hash entry，从哈希表移除        CCObject* pTarget = element->target;        HASH_DEL(m_pHashForUpdates, element);        free(element);        // target#release should be the last one to prevent        // a possible double-free. eg: If the [target dealloc] might want to remove it itself from there        pTarget->release(); //对对象执行一次release操作    }}

转载地址：http://ttsmi.baihongyu.com/