cocos2dx-lua 3.x 热更新方法

cocos2dx-lua中有assetmanagerex的c++实现类，也有绑定到lua。不过在3.10之前有缺陷，问题是当有文件下载失败时会陷入死循环，导致业务链断裂。不过网上有解决办法，可简单修改源码解决。不过个人还是建议可以把高于3.10版本以后的assetmanagerex代码移植到旧的3.x版本，也可以选择新项目使用3.10以后版本。

以下是lua版本使用热更新的方法

local AutoUpdateScene = class("AutoUpdateScene",cc.load("mvc").ViewBase)

local manifestPath = "project.manifest"
local storagePath = "update"

function AutoUpdateScene:onCreate()

    self._update_failed_count = 0

    local layer  = cc.Layer:create()

    local am = nil

    local function onEnter()

        local ttfConfig = {}
        ttfConfig.fontFilePath = "fonts/arial.ttf"
        ttfConfig.fontSize = 80

        local  progress = cc.Label:createWithTTF(ttfConfig,"0%",cc.VERTICAL_TEXT_ALIGNMENT_CENTER)
        progress:setPosition(cc.p(display.center.x,display.center.y + 50))
        layer:addChild(progress)

        am = cc.AssetsManagerEx:create(manifestPath,cc.FileUtils:getInstance():getWritablePath() .. storagePath)
        am:retain()

        if not am:getLocalManifest():isLoaded() then
            print("Fail to update assets,step skipped.")
            self:onFail("本地资源错误，请重新下载游戏。")
        else
            local function onUpdateEvent(event)
                local eventCode = event:getEventCode()
                print("====== assetsmanagerex error code:",eventCode)
                --[[ cc.EventAssetsManagerEx.EventCode = {
                    ERROR_NO_LOCAL_MANIFEST = 0,ERROR_DOWNLOAD_MANIFEST = 1,ERROR_PARSE_MANIFEST = 2,NEW_VERSION_FOUND = 3,ALREADY_UP_TO_DATE = 4,UPDATE_PROGRESSION = 5,ASSET_UPDATED = 6,ERROR_UPDATING = 7,UPDATE_FINISHED = 8,UPDATE_FAILED = 9,ERROR_DECOMPRESS = 10
                } ]]
                if eventCode == cc.EventAssetsManagerEx.EventCode.ERROR_NO_LOCAL_MANIFEST then
                    print("No local manifest file found,skip assets update.")
                    self:onFail(string.format("本地资源错误，请重新下载游戏。(错误码:%d)",eventCode))
                elseif eventCode == cc.EventAssetsManagerEx.EventCode.UPDATE_PROGRESSION then
                    local assetId = event:getAssetId()
                    local percent = event:getPercent()
                    local strInfo = ""
                    if assetId == cc.AssetsManagerExStatic.VERSION_ID then
                        strInfo = string.format("Version file: %d%%",percent)
                    elseif assetId == cc.AssetsManagerExStatic.MANIFEST_ID then
                        strInfo = string.format("Manifest file: %d%%",percent)
                    else
                        strInfo = string.format("%d%%",percent)
                    end
                    progress:setString(strInfo)
                    self:setLoadingProgress(event:getPercentByFile())
                elseif eventCode == cc.EventAssetsManagerEx.EventCode.ERROR_DOWNLOAD_MANIFEST or 
                       eventCode == cc.EventAssetsManagerEx.EventCode.ERROR_PARSE_MANIFEST then
                    print("Fail to download manifest file,update skipped.")
                    self:onFail(string.format("更新失败，请检查网络配置。(错误码:%d)",eventCode))
                elseif eventCode == cc.EventAssetsManagerEx.EventCode.ALREADY_UP_TO_DATE or 
                       eventCode == cc.EventAssetsManagerEx.EventCode.UPDATE_FINISHED then
                    print("Update finished.")
                    self:onSuccess()
                elseif eventCode == cc.EventAssetsManagerEx.EventCode.ERROR_UPDATING then
                    print("Asset ",event:getAssetId(),",event:getMessage())
                    -- self:onFail(string.format("更新资源失败，请检查网络后重试。(%d)",eventCode))
                elseif eventCode == cc.EventAssetsManagerEx.EventCode.UPDATE_FAILED then
                    print("Fail to download resource files.")
                    self._update_failed_count = self._update_failed_count + 1
                    if self._update_failed_count <= 3 then
                        print("try again")
                        am:downloadFailedAssets()
                    else
                        self:onFail(string.format("更新失败，请检查网络配置。(错误码:%d)",eventCode))
                    end
                elseif eventCode == cc.EventAssetsManagerEx.EventCode.NEW_VERSION_FOUND then
                    print("new version found.")
                    --am:update()
                elseif eventCode == cc.EventAssetsManagerEx.EventCode.ASSET_UPDATED then
                    print("assets updated.")
                elseif eventCode == cc.EventAssetsManagerEx.EventCode.ERROR_DECOMPRESS then
                    print("decompress error.")
                end
            end
            local listener = cc.EventListenerAssetsManagerEx:create(am,onUpdateEvent)
            cc.Director:getInstance():getEventDispatcher():addEventListenerWithFixedPriority(listener,1)
            
            am:update()
            --am:checkUpdate()
        end
    end

    local function onExit()
        am:release()
    end

    local function onNodeEvent(event)
        if "enter" == event then
            onEnter()
        elseif "exit" == event then
            onExit()
        end
    end
    layer:registerScriptHandler(onNodeEvent)

    self:addChild(layer)
end

function AutoUpdateScene:onFail(msg)
    print("====== update fail ======",msg)
    
    -- 热更新失败处理
end

function AutoUpdateScene:onSuccess()
    print("====== update success ======")

    local writablePath = cc.FileUtils:getInstance():getWritablePath()
    package.path = writablePath .. "update/src/?.lua;./?.lua;"

    -- 启动热更新后的场景
end

return AutoUpdateScene