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

// 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);
}