Cocos2dx 异步加载纹理

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1 异步加载资源

　　异步加载的执行过程主要在addImageAsync函数中: 判定当前路径对应的纹理是否已经加载，如果未加载，为该纹理创建一个AsyncStruct 数据结构存放该纹理数据，并加入至_requestMutex请求队列中。在创建的用于专门解析纹理的新线程LoadImage中，请求队列中的数据将被逐个解析至AsyncStruct .image中并加入已解析队列_responseQueue中。 在创建的计时器回调函数addImageAsyncCallBack中，将解析得到的image转换为最终的texture。
　　上述过程涉及两个线程：主线程GL Thread与子线程Load Thread，过程中两个重要的数据为AsyncStruct 与Image Data。其中AsyncStruct的创建与析构都在主线程中完成，Image Data在Load Thread中创建，在GL Thread中析构。
　　

  1. void TextureCache::addImageAsync(const std::string &path,const std::function<void(Texture2D*)>& callback,const std::string& callbackKey)
  2. {
  3.     Texture2D *texture = nullptr;
  4.     // 确定图片纹理是否已经加载
  5.     std::string fullpath = FileUtils::getInstance()->fullPathForFilename(path);
  6.     auto it = _textures.find(fullpath);
  7.     if (it != _textures.end())
  8.         texture = it->second;
  9.  
  10.     // 已加载 直接执行回调函数
  11.     if (texture != nullptr)
  12.     {
  13.         if (callback) callback(texture);
  14.         return;
  15.     }
  16.  
  17.     // 检查当前路径对应的文件是否存在
  18.     if (fullpath.empty() || !FileUtils::getInstance()->isFileExist(fullpath)) {
  19.         if (callback) callback(nullptr);
  20.         return;
  21.     }
  22.  
  23.     // lazy init
  24.     if (_loadingThread == nullptr)
  25.     {
  26.         // 创建一个新的线程 用于加载纹理
  27.         _loadingThread = new (std::nothrow) std::thread(&TextureCache::loadImage,this);
  28.         _needQuit = false;//线程是否终止的标志
  29.     }
  30.  
  31.     if (0 == _asyncRefCount)
  32.     {
  33.         // 创建定时器回调 用于将解析的image转为texture并执行回调函数
  34.         Director::getInstance()->getScheduler()->schedule(CC_SCHEDULE_SELECTOR(TextureCache::addImageAsyncCallBack),this,0,false);
  35.     }
  36.     ++_asyncRefCount;
  37.  
  38.     // 生成async struct，并加入至请求队列
  39.     AsyncStruct *data =
  40.       new (std::nothrow) AsyncStruct(fullpath,callback,callbackKey);
  41.  
  42.     // add async struct into queue
  43.     _asyncStructQueue.push_back(data); // 该队列在unbind函数中使用 在加载纹理过程中不使用
  44.     _requestMutex.lock();
  45.     _requestQueue.push_back(data);
  46.     _requestMutex.unlock();
  47.  
  48.     _sleepCondition.notify_one();
  49. }
  50.  
  51. // 解析资源的线程
  52. void TextureCache::loadImage()
  53. {
  54.     AsyncStruct *asyncStruct = nullptr;
  55.     std::mutex signalMutex;
  56.     std::unique_lock<std::mutex> signal(signalMutex);
  57.     while (!_needQuit)
  58.     {
  59.         // 从请求队列中取出待解析资源
  60.         _requestMutex.lock();
  61.         if (_requestQueue.empty())
  62.         {
  63.             asyncStruct = nullptr;
  64.         }
  65.         else
  66.         {
  67.             asyncStruct = _requestQueue.front();
  68.             _requestQueue.pop_front();
  69.         }
  70.         _requestMutex.unlock();
  71.  
  72.         if (nullptr == asyncStruct) {
  73.             _sleepCondition.wait(signal);
  74.             continue;
  75.         }
  76.  
  77.         // load image
  78.         asyncStruct->loadSuccess = asyncStruct->image.initWithImageFileThreadSafe(asyncStruct->filename);
  79.  
  80.         // push the asyncStruct to response queue
  81.         _responseMutex.lock();
  82.         _responseQueue.push_back(asyncStruct);
  83.         _responseMutex.unlock();
  84.     }
  85. }
  86.  
  87. void TextureCache::addImageAsyncCallBack(float /*dt*/)
  88. {
  89.     Texture2D *texture = nullptr;
  90.     AsyncStruct *asyncStruct = nullptr;
  91.     while (true) // 轮询解析队列中的image 
  92.     {
  93.         // pop an AsyncStruct from response queue
  94.         _responseMutex.lock();
  95.         if (_responseQueue.empty())
  96.         {
  97.             asyncStruct = nullptr;
  98.         }
  99.         else
  100.         {
  101.             asyncStruct = _responseQueue.front();
  102.             _responseQueue.pop_front();
  103.  
  104.             // 保持_asyncStructQueue 与 _responseQueue的同步
  105.             CC_ASSERT(asyncStruct == _asyncStructQueue.front());
  106.             _asyncStructQueue.pop_front();
  107.         }
  108.         _responseMutex.unlock();
  109.  
  110.         if (nullptr == asyncStruct) {
  111.             break;
  112.         }
  113.  
  114.         // check the image has been convert to texture or not
  115.         auto it = _textures.find(asyncStruct->filename);
  116.         if (it != _textures.end()) // 检查当前纹理资源是否已被加载
  117.         {
  118.             texture = it->second;
  119.         }
  120.         else
  121.         {
  122.             // convert image to texture
  123.             if (asyncStruct->loadSuccess)
  124.             {
  125.                 Image* image = &(asyncStruct->image);
  126.                 // generate texture in render thread
  127.                 texture = new (std::nothrow) Texture2D();
  128.  
  129.                 texture->initWithImage(image,asyncStruct->pixelFormat);
  130.                 //parse 9-patch info
  131.                 this->parseNinePatchImage(image,texture,asyncStruct->filename);
  132. #if CC_ENABLE_CACHE_TEXTURE_DATA
  133.                 // cache the texture file name
  134.                 VolatileTextureMgr::addImageTexture(texture,asyncStruct->filename);
  135. #endif
  136.                 // cache the texture. retain it,since it is added in the map
  137.                 _textures.emplace(asyncStruct->filename,texture);
  138.                 texture->retain(); // 为何要retain: 下一帧不自动释放该纹理，纹理的释放由程序手动控制
  139.                 texture->autorelease();
  140.             }
  141.             else {
  142.                 texture = nullptr;
  143.                 CCLOG("cocos2d: Failed to call TextureCache::addImageAsync(%s)",asyncStruct->filename.c_str());
  144.             }
  145.         }
  146.  
  147.         // 执行回调函数
  148.         if (asyncStruct->callback)
  149.         {
  150.             (asyncStruct->callback)(texture);
  151.         }
  152.  
  153.         // release the asyncStruct
  154.         delete asyncStruct;
  155.         --_asyncRefCount;
  156.     }
  157.  
  158.     if (0 == _asyncRefCount) // 所有异步加载过程均已完成 销毁计时器回调
  159.     {
  160.         Director::getInstance()->getScheduler()->unschedule(CC_SCHEDULE_SELECTOR(TextureCache::addImageAsyncCallBack),this);
  161.     }
  162. }

2 纹理中关键帧的检索

检索之前，首先需要将一整张纹理按照区域切割成各个关键帧，并建立帧名与帧之间的map映射表。addSpriteFramesWithFile完成了这一过程，该函数为已加载完成的纹理数据与对应的plist文件构建映射关系。

  1. void SpriteFrameCache::addSpriteFramesWithFile(const std::string& plist,Texture2D *texture)
  2. {
  3.     if (_loadedFileNames->find(plist) != _loadedFileNames->end())
  4.     {
  5.         return; // We already added it
  6.     }
  7.  
  8.     std::string fullPath = FileUtils::getInstance()->fullPathForFilename(plist);// plist全路径
  9.     ValueMap dict = FileUtils::getInstance()->getValueMapFromFile(fullPath); // plist是XML文件，cocos将其解析为key-value的map结构
  10.  
  11.     addSpriteFramesWithDictionary(dict,texture);
  12.     _loadedFileNames->insert(plist);
  13. }
  14.  
  15. // 从texture中取出相应区域spriteframe
  16. void SpriteFrameCache::addSpriteFramesWithDictionary(ValueMap& dictionary,Texture2D* texture)
  17. {
  18.     /* 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+ */
  19.  
  20.     if (dictionary["frames"].getType() != cocos2d::Value::Type::MAP)
  21.         return;
  22.  
  23.     ValueMap& framesDict = dictionary["frames"].asValueMap(); // 存放每一帧图片路径、大小、偏移、对应的纹理区域位置等属性
  24.     int format = 0;
  25.  
  26.     Size textureSize;
  27.  
  28.     // get the format
  29.     if (dictionary.find("Metadata") != dictionary.end())
  30.     {
  31.         ValueMap& MetadataDict = dictionary["Metadata"].asValueMap(); // Metadata中存放纹理格式、纹理大小、纹理名称等纹理属性
  32.         format = MetadataDict["format"].asInt();
  33.         if(MetadataDict.find("size") != MetadataDict.end())
  34.         {
  35.             textureSize = SizeFromString(MetadataDict["size"].asString());
  36.         }
  37.     }
  38.  
  39.     // check the format
  40.     CCASSERT(format >=0 && format <= 3,"format is not supported for SpriteFrameCache addSpriteFramesWithDictionary:textureFilename:");
  41.  
  42.     auto textureFileName = Director::getInstance()->getTextureCache()->getTextureFilePath(texture);
  43.     Image* image = nullptr;
  44.     NinePatchImageParser parser;
  45.     for (auto& iter : framesDict)
  46.     {
  47.         ValueMap& frameDict = iter.second.asValueMap();
  48.         std::string spriteFrameName = iter.first;
  49.         SpriteFrame* spriteFrame = _spriteFrames.at(spriteFrameName);
  50.         if (spriteFrame)
  51.         {
  52.             continue; // 当前帧已加入至关键帧集合 无需处理
  53.         }
  54.  
  55.         if(format == 0) 
  56.         {
  57.             float x = frameDict["x"].asFloat();
  58.             float y = frameDict["y"].asFloat();
  59.             float w = frameDict["width"].asFloat();
  60.             float h = frameDict["height"].asFloat();
  61.             float ox = frameDict["offsetX"].asFloat();
  62.             float oy = frameDict["offsetY"].asFloat();
  63.             int ow = frameDict["originalWidth"].asInt();
  64.             int oh = frameDict["originalHeight"].asInt();
  65.             // check ow/oh
  66.             if(!ow || !oh)
  67.             {
  68.                 CCLOGWARN("cocos2d: WARNING: originalWidth/Height not found on the SpriteFrame. AnchorPoint won't work as expected. Regenerate the .plist");
  69.             }
  70.             // abs ow/oh
  71.             ow = std::abs(ow);
  72.             oh = std::abs(oh);
  73.             // create frame
  74.             spriteFrame = SpriteFrame::createWithTexture(texture,Rect(x,y,w,h),false,Vec2(ox,oy),Size((float)ow,(float)oh)
  75.                                                          );
  76.         } 
  77.         else if(format == 1 || format == 2) 
  78.         {
  79.             Rect frame = RectFromString(frameDict["frame"].asString());
  80.             bool rotated = false;
  81.  
  82.             // rotation
  83.             if (format == 2)
  84.             {
  85.                 rotated = frameDict["rotated"].asBool();
  86.             }
  87.  
  88.             Vec2 offset = PointFromString(frameDict["offset"].asString());
  89.             Size sourceSize = SizeFromString(frameDict["sourceSize"].asString());
  90.  
  91.             // create frame
  92.             spriteFrame = SpriteFrame::createWithTexture(texture,frame,rotated,offset,sourceSize
  93.                                                          );
  94.         } 
  95.         else if (format == 3)
  96.         {
  97.             // get values
  98.             Size spriteSize = SizeFromString(frameDict["spriteSize"].asString());
  99.             Vec2 spriteOffset = PointFromString(frameDict["spriteOffset"].asString());
  100.             Size spriteSourceSize = SizeFromString(frameDict["spriteSourceSize"].asString());
  101.             Rect textureRect = RectFromString(frameDict["textureRect"].asString());
  102.             bool textureRotated = frameDict["textureRotated"].asBool();
  103.  
  104.             // get aliases
  105.             ValueVector& aliases = frameDict["aliases"].asValueVector();
  106.  
  107.             for(const auto &value : aliases) {
  108.                 std::string oneAlias = value.asString();
  109.                 if (_spriteFramesAliases.find(oneAlias) != _spriteFramesAliases.end())
  110.                 {
  111.                     CCLOGWARN("cocos2d: WARNING: an alias with name %s already exists",oneAlias.c_str());
  112.                 }
  113.  
  114.                 _spriteFramesAliases[oneAlias] = Value(spriteFrameName);
  115.             }
  116.  
  117.             // create frame
  118.             spriteFrame = SpriteFrame::createWithTexture(texture,Rect(textureRect.origin.x,textureRect.origin.y,spriteSize.width,spriteSize.height),textureRotated,spriteOffset,spriteSourceSize);
  119.  
  120.             if(frameDict.find("vertices") != frameDict.end())
  121.             {
  122.                 std::vector<int> vertices;
  123.                 parseIntegerList(frameDict["vertices"].asString(),vertices);
  124.                 std::vector<int> verticesUV;
  125.                 parseIntegerList(frameDict["verticesUV"].asString(),verticesUV);
  126.                 std::vector<int> indices;
  127.                 parseIntegerList(frameDict["triangles"].asString(),indices);
  128.  
  129.                 PolygonInfo info;
  130.                 initializePolygonInfo(textureSize,spriteSourceSize,vertices,verticesUV,indices,info);
  131.                 spriteFrame->setPolygonInfo(info);
  132.             }
  133.             if (frameDict.find("anchor") != frameDict.end())
  134.             {
  135.                 spriteFrame->setAnchorPoint(PointFromString(frameDict["anchor"].asString()));
  136.             }
  137.         }
  138.  
  139.         bool flag = NinePatchImageParser::isNinePatchImage(spriteFrameName);
  140.         if(flag)
  141.         {
  142.             if (image == nullptr) {
  143.                 image = new (std::nothrow) Image();
  144.                 image->initWithImageFile(textureFileName);
  145.             }
  146.             parser.setSpriteFrameInfo(image,spriteFrame->getRectInPixels(),spriteFrame->isRotated());
  147.             texture->addSpriteFrameCapInset(spriteFrame,parser.parseCapInset());
  148.         }
  149.         // add sprite frame
  150.         _spriteFrames.insert(spriteFrameName,spriteFrame);
  151.     }
  152.     CC_SAFE_DELETE(image);
  153. }
  154.  
  155. // 基于frameName检索得到SpriteFrame
  156. SpriteFrame* SpriteFrameCache::getSpriteFrameByName(const std::string& name)
  157. {
  158.     SpriteFrame* frame = _spriteFrames.at(name);
  159.     if (!frame)
  160.     {
  161.         // try alias dictionary
  162.         if (_spriteFramesAliases.find(name) != _spriteFramesAliases.end())
  163.         {
  164.             std::string key = _spriteFramesAliases[name].asString();
  165.             if (!key.empty())
  166.             {
  167.                 frame = _spriteFrames.at(key);
  168.                 if (!frame)
  169.                 {
  170.                     CCLOG("cocos2d: SpriteFrameCache: Frame aliases '%s' isn't found",key.c_str());
  171.                 }
  172.             }
  173.         }
  174.         else
  175.         {
  176.             CCLOG("cocos2d: SpriteFrameCache: Frame '%s' isn't found",name.c_str());
  177.         }
  178.     }
  179.     return frame;
  180. }

3 lua层的接口调用

  1. local createAni = function ( texture )
  2.     -- 回调函数时将传入已加载的纹理
  3.     local testSp = cc.Sprite:createWithTexture(texture)
  4.     self:addChild(testSp)
  5.  
  6.     local ani = cc.Animation:create()
  7.     ani:setDelayPerUnit(0.12)
  8.     ani:setRestoreOriginalFrame(true) -- 动画停止时显示为起始图片
  9.     for i=1,num do
  10.         local frameName = getFrameName(i)
  11.         local frame = cc.SpriteFrameCache:getInstance():getSpriteFrameByName(frameName)
  12.         if frame then
  13.             ani:addSpriteFrame(frame)
  14.         end
  15.         -- 关键帧全部加载完毕 播放动画
  16.         if i == num then
  17.             self:stopAllActions()
  18.             local action = cc.Animation:create(ani)
  19.             self:runAction(action)
  20.         end
  21.     end
  22. end
  23. local textureName = getTextureName() or "" -- 禁止向cocos接口中传入nil 避免宕机
  24. cc.Director:getInstance():getTextureCache():addImageAsync(textureName,createAni)

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