cocos2dx学习之CCTextureCache

CCTextureCache原理大致分几步：

创建线程，用于后台加载
将对于需要加载的图片放入队列中
callback函数设定，用于将加载完成的图片转为纹理，等待使用其调用是由CCTimer::update调用的。

addImageAsyncCallBack函数在处理完纹理转换，还会调用addImageAsync传入的SEL_CallFuncO selector，实现用户加载图片纹理之后的具体处理。

voidCCTextureCache::addImageAsync(constchar *path, CCObject *target, SEL_CallFuncO selector){
    CCAssert(path != NULL, "TextureCache: fileimage MUST not be NULL"); 
    CCTexture2D *texture = NULL;
    
    // optimization
    std::string pathKey = path;
    CCFileUtils::ccRemoveHDSuffixFromFile(pathKey);
    
    pathKey = CCFileUtils::fullPathFromRelativePath(pathKey.c_str());
    texture = m_pTextures->objectForKey(pathKey); //根据pathkey查看是否纹理已经加载过，如果已经有了，则不重复加载
    std::string fullpath = pathKey;
    if (texture != NULL)
    {
        if (target && selector)
        {
            (target->*selector)(texture);
        }
            
        return;
    }
       if (target)
    {
        target->retain();
    }
    
    // lazy init
    static bool firstRun = true;
    if (firstRun)
    {            
        s_pAsyncStructQueue = new queue<AsyncStruct*>();
        s_pImageQueue = new queue<ImageInfo*>();        
    
        pthread_mutex_init(&s_asyncStructQueueMutex, NULL);
        sem_init(&s_sem, 0, 0);
        pthread_mutex_init(&s_ImageInfoMutex, NULL);
        pthread_create(&s_loadingThread, NULL, loadImage, NULL);//创建新的线程，用于后台加载图片

        //创建调度队列，用来根据已加载的图片进行纹理转换
        CCScheduler::sharedScheduler()->scheduleSelector(schedule_selector(CCTextureCache::addImageAsyncCallBack), this, 0, false);
        need_quit = false;
        firstRun = false;
    }
    
    // generate async struct
    AsyncStruct *data = new AsyncStruct();
    data->filename = fullpath.c_str();
    data->target = target;
    data->selector = selector;
    
    // add async struct into queue
    pthread_mutex_lock(&s_asyncStructQueueMutex);
    s_pAsyncStructQueue->push(data);//将需要加载的图片放入队列中
    pthread_mutex_unlock(&s_asyncStructQueueMutex);
    
    sem_post(&s_sem);
}

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Published

23 January 2015

cocos2dx学习之CCTextureCache Life is but a span.

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