1 //使用條件變量暫停主線程
 2 //繼承了CCFileUtils文件
 3 unsigned char* QFileUtils::getFileData(const char* pszFileName, const char* pszMode, unsigned long * pSize)
 4 {
 5     auto download = QDownloadSmallPack::getInstance();
 6     auto index = QIndex::getInstance();
 7     if (download->isStartCheckRes())
 8     {
 9         bool hasFile = download->checkFile(pszFileName);
10         if (!hasFile)
11         {
12             QIndex::IndexEntry* filePathInIndex = index->getFilePathByIndex(pszFileName);
13             if (filePathInIndex && !filePathInIndex->name.empty())
14             {
15                 std::unique_lock<std::mutex> lock{_m};
16                 download->downloadFile(filePathInIndex, _cond_var);
17                 
18                 if (!download->isDownloadOK)
19                 {
20                     _cond_var.wait(lock, [download](){ return download->isDownloadOK; });
21                 }
22                 
23             }
24         }
25     }
26 
27     return CCFileUtils::getFileData(pszFileName, pszMode, pSize);
28 }

- (id)init: (const cocos2d::network::DownloaderApple*)o hints:(const cocos2d::network::DownloaderHints&) hints
{
    DLLOG("Construct DownloaderAppleImpl %p", self);
    // save outer task ref
    _outer = o;
    _hints = hints;

    // create task dictionary
    self.taskDict = [NSMutableDictionary dictionary];

    // create download session
    NSURLSessionConfiguration *defaultConfig = [NSURLSessionConfiguration defaultSessionConfiguration];
    if (hints.callBackInMainThread)
    {
//在主線程中回調(diào)
        self.downloadSession = [NSURLSession sessionWithConfiguration:defaultConfig delegate:self delegateQueue:[NSOperationQueue mainQueue]];
    }
    else
    {
//在子線程中回調(diào)
        self.downloadSession = [NSURLSession sessionWithConfiguration:defaultConfig delegate:self delegateQueue:nil];
    }
    
//    self.downloadSession.sessionDescription = kCurrentSession;
    return self;
}

//其他兩個回調(diào)做同樣的修改就好    
void onProgress(final int id, final long downloadBytes, final long downloadNow, final long downloadTotal) {
        DownloadTask task = (DownloadTask)_taskMap.get(id);
        if (null != task) {
            task.bytesReceived = downloadBytes;
            task.totalBytesReceived = downloadNow;
            task.totalBytesExpected = downloadTotal;
        }
        if (_callBackInMainThread){
            Cocos2dxHelper.getActivity().runOnGLThread(new Runnable() {
                @Override
                public void run() {
                    nativeOnProgress(_id, id, downloadBytes, downloadNow, downloadTotal);
                }
            });
        }else {
//在子線程中回調(diào)
            new Runnable() {
                @Override
                public void run() {
                    nativeOnProgress(_id, id, downloadBytes, downloadNow, downloadTotal);
                }
            }.run();
        }
    }

//cv是getfiledata中使用的條件變量    
_downloader->onFileTaskSuccess = [this, &cv](const cocos2d::network::DownloadTask& task)
    {
//做一些游戲自己的檢測邏輯，確認(rèn)文件下載完成之后這里設(shè)置條件變量并且通知主線程恢復(fù)
            isDownloadOK = true;
            cv.notify_all();
    };