setDefaultAlphaPixelFormat bug addSpriteFrames 異步加載資源

function display.addSpriteFrames(plistFilename, image, handler)
    local async = type(handler) == "function"
    local asyncHandler = nil
    if async then
        asyncHandler = function()
            local texture = sharedTextureCache:getTextureForKey(image)
            assert(texture, string.format("The texture %s, %s is unavailable.", plistFilename, image))
            sharedSpriteFrameCache:addSpriteFrames(plistFilename, texture)
            handler(plistFilename, image)
        end
    end

    if display.TEXTURES_PIXEL_FORMAT[image] then
        cc.Texture2D:setDefaultAlphaPixelFormat(display.TEXTURES_PIXEL_FORMAT[image])
        if async then
            sharedTextureCache:addImageAsync(image, asyncHandler)
        else
            sharedSpriteFrameCache:addSpriteFrames(plistFilename, image)
        end
        cc.Texture2D:setDefaultAlphaPixelFormat(cc.TEXTURE2_D_PIXEL_FORMAT_RGB_A8888)
    else
        if async then
            sharedTextureCache:addImageAsync(image, asyncHandler)
        else
            sharedSpriteFrameCache:addSpriteFrames(plistFilename, image)
        end
    end
end

導致原因：因爲異步加載後會取出當前Texture2D::getDefaultAlphaPixelFormat()的格式，加載需要一定時間，當前格式就被更改了。當加載好的時候再去轉換格式，就不能取到加載的時候的pixelformat了。。。處理把pixelformat 保存在異步加載中。然後加載好的時候不用取默認格式了。

修改 TextureCache.cpp 文件 有3處修改地方

第一處 

AsyncStruct *data = new (std::nothrow) AsyncStruct(fullpath, callback)

修改成

AsyncStruct *data = new (std::nothrow) AsyncStruct(fullpath, callback, Texture2D::getDefaultAlphaPixelFormat())

void TextureCache::addImageAsync(const std::string &path, const std::function<void(Texture2D*)>& callback)
{
    Texture2D *texture = nullptr;

    std::string fullpath = FileUtils::getInstance()->fullPathForFilename(path);

    auto it = _textures.find(fullpath);
    if( it != _textures.end() )
        texture = it->second;

    if (texture != nullptr)
    {
        if (callback) callback(texture);
        return;
    }

    // check if file exists
    if ( fullpath.empty() || ! FileUtils::getInstance()->isFileExist( fullpath ) ) {
        if (callback) callback(nullptr);
        return;
    }

    // lazy init
    if (_loadingThread == nullptr)
    {
        // create a new thread to load images
        _loadingThread = new (std::nothrow) std::thread(&TextureCache::loadImage, this);
        _needQuit = false;
    }

    if (0 == _asyncRefCount)
    {
        Director::getInstance()->getScheduler()->schedule(CC_SCHEDULE_SELECTOR(TextureCache::addImageAsyncCallBack), this, 0, false);
    }

    ++_asyncRefCount;

    // generate async struct
    /* 異步加載設置紋理格式 */
    AsyncStruct *data = new (std::nothrow) AsyncStruct(fullpath, callback, Texture2D::getDefaultAlphaPixelFormat());
    //AsyncStruct *data = new (std::nothrow) AsyncStruct(fullpath, callback);
    // add async struct into queue
    _asyncStructQueue.push_back(data);
    _requestMutex.lock();
    _requestQueue.push_back(data);
    _requestMutex.unlock();

    _sleepCondition.notify_one();
}

第二處

texture->initWithImage(image)

修改成

texture->initWithImage(image, asyncStruct->format)

void TextureCache::addImageAsyncCallBack(float dt)
{
    Texture2D *texture = nullptr;
    AsyncStruct *asyncStruct = nullptr;
    while (true)
    {
        // pop an AsyncStruct from response queue
        _responseMutex.lock();
        if(_responseQueue.empty())
        {
            asyncStruct = nullptr;
        }else
        {
            asyncStruct = _responseQueue.front();
            _responseQueue.pop_front();
            
            // the asyncStruct's sequence order in _asyncStructQueue must equal to the order in _responseQueue
            CC_ASSERT(asyncStruct == _asyncStructQueue.front());
            _asyncStructQueue.pop_front();
        }
        _responseMutex.unlock();
        
        if (nullptr == asyncStruct) {
            break;
        }
        
        // check the image has been convert to texture or not
        auto it = _textures.find(asyncStruct->filename);
        if(it != _textures.end())
        {
            texture = it->second;
        }
        else
        {
            // convert image to texture
            if (asyncStruct->loadSuccess)
            {
                Image* image = &(asyncStruct->image);
                // generate texture in render thread
                texture = new (std::nothrow) Texture2D();
                /* 異步加載設置紋理格式 */
                texture->initWithImage(image, asyncStruct->format);
                //texture->initWithImage(image);
                //parse 9-patch info
                this->parseNinePatchImage(image, texture, asyncStruct->filename);
#if CC_ENABLE_CACHE_TEXTURE_DATA
                // cache the texture file name
                VolatileTextureMgr::addImageTexture(texture, asyncStruct->filename);
#endif
                // cache the texture. retain it, since it is added in the map
                _textures.insert( std::make_pair(asyncStruct->filename, texture) );
                texture->retain();
                
                texture->autorelease();
            } else {
                texture = nullptr;
                CCLOG("cocos2d: failed to call TextureCache::addImageAsync(%s)", asyncStruct->filename.c_str());
            }
        }
        
        // call callback function
        if (asyncStruct->callback)
        {
            (asyncStruct->callback)(texture);
        }

        // release the asyncStruct
        delete asyncStruct;
        --_asyncRefCount;
    }

    if (0 == _asyncRefCount)
    {
        Director::getInstance()->getScheduler()->unschedule(CC_SCHEDULE_SELECTOR(TextureCache::addImageAsyncCallBack), this);
    }
}

第三處

struct TextureCache::AsyncStruct
{
public:
    AsyncStruct(const std::string& fn, std::function<void(Texture2D*)> f) : filename(fn), callback(f), loadSuccess(false) {}
    
    std::string filename;
    std::function<void(Texture2D*)> callback;
    Image image;
    bool loadSuccess;
};

修改成

struct TextureCache::AsyncStruct
{
public:
    AsyncStruct(const std::string& fn, std::function<void(Texture2D*)> f, Texture2D::PixelFormat ft) : filename(fn), callback(f), format(ft), loadSuccess(false) {}
    
    std::string filename;
    std::function<void(Texture2D*)> callback;
    Image image;
    Texture2D::PixelFormat format;
    bool loadSuccess;
};