cocos2d-x lua 使用http，下载图片, POST JSON

version: cocos2d-x 3.6

1.使用http post json与服务器交互

require("src/cocos/cocos2d/json")
require("src/cocos/network/NetworkConstants")

-- post json
local xhr = cc.XMLHttpRequest:new()
xhr.responseType = cc.XMLHTTPREQUEST_RESPONSE_JSON
xhr:setRequestHeader("Content-Type", "application/json")
xhr:open("POST", "www.baidu.com")
local function loginCallback()
        print("xhr.readyState is:", xhr.readyState, "xhr.status is: ", xhr.status)
    if xhr.readyState == 4 and (xhr.status >= 200 and xhr.status < 207) then
        local response = xhr.response
        local output = json.decode(response)
        -- print
        table.foreach(output, function(i, v) print (i, v) end)
        
                -- success ...
    else
        -- fail ...
    end
end
xhr:registerScriptHandler(loginCallback)
xhr:send(sendJson)

2.使用http get下载网络图片

-- get (image)

pSprite:retain()  -- a sprite
local xhr = cc.XMLHttpRequest:new()

-- tag
xhr._urlFileName = urlFileName
xhr._urlSprite = pSprite

xhr.responseType = cc.XMLHTTPREQUEST_RESPONSE_STRING
xhr:open("GET", "http://cocos2d-x.org/s/images/img-cocos2dx.jpg")
local function onDownloadImage()
        print("xhr.readyState is:", xhr.readyState, "xhr.status is: ", xhr.status)
    if xhr.readyState == 4 and (xhr.status >= 200 and xhr.status < 207) then
        local fileData = xhr.response
        local fullFileName = cc.FileUtils:getInstance():getWritablePath() .. "/" .. xhr._urlFileName
        local file = io.open(fullFileName,"wb")
        file:write(fileData)
        file:close()
        local texture2d = cc.Director:getInstance():getTextureCache():addImage(fullFileName)
        local pSprite = xhr._urlSprite
        if texture2d then
            pSprite:setTexture(texture2d)
        end
        pSprite:release() -- be careful
    end
end
xhr:registerScriptHandler(onDownloadImage)
xhr:send()

• 在使用xhr时，可以添加自己的数据（如：xhr._urlSprite = pSprite），存放用户的临时数据，方便返回时使用。