cocos2d-x 2.2.3 通过plist创建sprite的过程简单分析转

原始文章地址：http://www.jb51.cc/article/p-zqlfzpgw-bbv.html

// 通过plist载入缓存
CCSpriteFrameCache::sharedSpriteFrameCache()->addSpriteFramesWithFile("test.plist");
// 通过缓存载入sprite
CCSprite* sp = CCSprite::createWithSpriteFrameName("test01.png");

以上2句代码，可以通过plist创建一个sprite，简单分析下过程。

通过plist载入缓存
首先是通过plist载入缓存，跟踪到源码看到如下片段：

void CCSpriteFrameCache::addSpriteFramesWithFile(const char *pszPlist)
{
    CCAssert(pszPlist,"plist filename should not be NULL");
    // 判断是否加载过该文件 如果没加载过，才做以下这些事情
    if (m_pLoadedFileNames->find(pszPlist) == m_pLoadedFileNames->end())
    {
    // 获取完整路径名，创建dict
        std::string fullPath = CCFileUtils::sharedFileUtils()->fullPathForFilename(pszPlist);
        CCDictionary *dict = CCDictionary::createWithContentsOfFileThreadSafe(fullPath.c_str());

        string texturePath("");
    // 尝试获取textureFileName，如果需要指定，格式大概长这样：
    // <key>Metadata</key>
    // <dict>
    // <key>textureFileName</key>
    // <string>tex.png</string>
    // </dictt>
    // 指定载入tex.png
        CCDictionary* MetadataDict = (CCDictionary*)dict->objectForKey("Metadata");
        if (MetadataDict)
        {
            // try to read texture file name from Meta data
            texturePath = MetadataDict->valueForKey("textureFileName")->getCString();
        }
    // 如果有指定tex文件，则直接查找完整路径
        if (! texturePath.empty())
        {
            // build texture path relative to plist file
            texturePath = CCFileUtils::sharedFileUtils()->fullPathFromrelativeFile(texturePath.c_str(),pszPlist);
        }
        else    // 没有指定tex文件，载入plist对应的png，比如plist文件名：abc.plist，则载入的png为：abc.png
        {
            // build texture path by replacing file extension
            texturePath = pszPlist;

            // remove .xxx
            size_t startPos = texturePath.find_last_of("."); 
            texturePath = texturePath.erase(startPos);

            // append .png
            texturePath = texturePath.append(".png");

            cclOG("cocos2d: CCSpriteFrameCache: Trying to use file %s as texture",texturePath.c_str());
        }
    // 载入图片
        CCTexture2D *pTexture = CCTextureCache::sharedTextureCache()->addImage(texturePath.c_str());

        if (pTexture)
        {
        // 载入spriteFrames
            addSpriteFramesWithDictionary(dict,pTexture);
            m_pLoadedFileNames->insert(pszPlist);
        }
        else
        {
            cclOG("cocos2d: CCSpriteFrameCache: Couldn't load texture");
        }

        dict->release();
    }

}

然后到了这里：

void CCSpriteFrameCache::addSpriteFramesWithDictionary(CCDictionary* dictionary,CCTexture2D *pobTexture)
{
/*
// format 4种格式支持
Supported Zwoptex Formats:

ZWTCoordinatesFormatOptionXMLLegacy = 0,// Flash Version
ZWTCoordinatesFormatOptionXML1_0 = 1,// Desktop Version 0.0 - 0.4b
ZWTCoordinatesFormatOptionXML1_1 = 2,// Desktop Version 1.0.0 - 1.0.1
ZWTCoordinatesFormatOptionXML1_2 = 3,// Desktop Version 1.0.2+
*/
// 分离2个dict
CCDictionary *MetadataDict = (CCDictionary*)dictionary->objectForKey("Metadata");
CCDictionary *framesDict = (CCDictionary*)dictionary->objectForKey("frames");
int format = 0;
// 从Metadata获取格式 默认为0
if(MetadataDict != NULL) 
{
    format = MetadataDict->valueForKey("format")->intValue();
}
// 检测format 支持0-3
CCAssert(format >=0 && format <= 3,"format is not supported for CCSpriteFrameCache addSpriteFramesWithDictionary:textureFilename:");
// 遍历frames
CCDictElement* pElement = NULL;
CCDICT_FOREACH(framesDict,pElement)
{
    CCDictionary* frameDict = (CCDictionary*)pElement->getobject();
    std::string spriteFrameName = pElement->getStrKey();    // 取key作为sprite名
// 如果已经加载过 不再处理
    CCSpriteFrame* spriteFrame = (CCSpriteFrame*)m_pSpriteFrames->objectForKey(spriteFrameName);
    if (spriteFrame)
    {
        continue;
    }
// 根据format处理
    if(format == 0) 
    {
        float x = frameDict->valueForKey("x")->floatValue();
        float y = frameDict->valueForKey("y")->floatValue();
        float w = frameDict->valueForKey("width")->floatValue();
        float h = frameDict->valueForKey("height")->floatValue();
        float ox = frameDict->valueForKey("offsetX")->floatValue();
        float oy = frameDict->valueForKey("offsetY")->floatValue();
        int ow = frameDict->valueForKey("originalWidth")->intValue();
        int oh = frameDict->valueForKey("originalHeight")->intValue();
        // check ow/oh
        if(!ow || !oh)
        {
            cclOGWARN("cocos2d: WARNING: originalWidth/Height not found on the CCSpriteFrame. AnchorPoint won't work as expected. Regenrate the .plist");
        }
        // abs ow/oh
        ow = abs(ow);
        oh = abs(oh);
        // create frame
        spriteFrame = new CCSpriteFrame();
    // 对照一下，大概就明白了
    // initWithTexture(CCTexture2D* pobTexture,const CCRect& rect,bool rotated,const CCPoint& offset,const CCSize& originalSize)
        spriteFrame->initWithTexture(pobTexture,CCRectMake(x,y,w,h),false,CCPointMake(ox,oy),CCSizeMake((float)ow,(float)oh)
                                    );
    } 
...// 以下类似

    // 加入缓存，名字用spriteFrameName <span style="font-family: Arial,Helvetica,sans-serif;"> m_pSpriteFrames是一个dict</span>
    m_pSpriteFrames->setobject(spriteFrame,spriteFrameName);
    spriteFrame->release();
}

}

于是，这部分的大概流程就是：
载入plist，载入texture，根据plist选择texture的区域，载入spriteFrame，加入到缓存。

通过缓存载入sprite

CCSprite* CCSprite::createWithSpriteFrameName(const char *pszSpriteFrameName)
{
    // 从缓存里取对应名字的spriteFrame
    CCSpriteFrame *pFrame = CCSpriteFrameCache::sharedSpriteFrameCache()->spriteFrameByName(pszSpriteFrameName);

#if COCOS2D_DEBUG > 0
    char msg[256] = {0};
    sprintf(msg,"Invalid spriteFrameName: %s",pszSpriteFrameName);
    CCAssert(pFrame != NULL,msg);
#endif

    return createWithSpriteFrame(pFrame);
}