cocos2dx-lua http请求下载图片，使用XMLHttpRequest类

local downloader = {}

--数据拆分，以没1024*5字节拆成一段，打包写入文件    (拆完再拼接，转成字符串)

local function getStrData(response)
    local totalSize = table.getn(response)
    local onePart = 1024*5
    local partData = ""
    local packTimes = math.floor(totalSize/onePart)

    print("文件大小： : ",totalSize )
    --print(" -- > pack size,times : ",totalSize,packTimes)
    for i=1,packTimes do
        local partUnPack = string.char(unpack(response,1+(i-1)*onePart,i*onePart) )
        partData = partData..partUnPack
        --print(" -- > pack new part : ",1+(i-1)*onePart,i*onePart)
    end
    --print(" -- > pack end part : ",packTimes*onePart+1,totalSize)
    local endUnpack = string.char(unpack(response,packTimes*onePart+1,totalSize) )
    partData = partData..endUnpack
    return partData
end

--下载图片
function downloader:DownLoadImage(url,saveName,callBack)
    local xhr = cc.XMLHttpRequest:new()
    xhr.responseType = cc.XMLHTTPREQUEST_RESPONSE_ARRAY_BUFFER
    xhr:open("GET",url)

    --self.callBack = callBack

    local function onReadyStateChanged()
        print("---------net--------- xhr.readyState  xhr.status",xhr.readyState,xhr.status)
        if xhr.readyState == 4 and (xhr.status >= 200 and xhr.status < 207) then
            print(" ---> 下载图片返回数据 : ",xhr.statusText )
            local response   = xhr.response
            local strInfo = getStrData(response)
            io.writefile("user/"..saveName,strInfo,"w+b")
            --self:callback("down load ok",saveName)
            --self.
            callBack(saveName)
        else
            print(" --- > error xhr.readyState is:","xhr.status is: ",xhr.status)
            self:callbackErr(xhr.readyState,xhr.status)
        end
        if xhr.status == 200 then
            print("xhr.readyState  xhr.status",xhr.status)
            --req.callback(code,fullFileName,req)
        end

        xhr:unregisterScriptHandler()
    end

    xhr:registerScriptHandler(onReadyStateChanged)
    xhr:send()
end

cc.exports.HttpFileDownLoadSimple = downloader

return downloader

local list = {}
    list[1] = {id = 666,url = "http://life.southmoney.com/tuwen/UploadFiles_6871/201809/20180925104703150.jpg"}
    list[2] = {id = 777,url = "http://img.52z.com/upload/news/image/20180914/20180914034357_53554.jpg"}

    function downCallBack(name)
        print(name)
    end

    local u1 = list[1]
    local u2 = list[2]


    HttpFileDownLoadSimple:DownLoadImage(u1.url,"head"..u1.id..".jpg",downCallBack)