【Cocos Creator】拒绝 evalString 进行回调，使用 JSB 进行手动绑定（流程篇）

Cocos2dxJavascriptJavaBridge.evalString("window.sample.testEval('" + param + "',JSON.stringify(" + jsonObj + "))");

if(cc.sys.isNative && cc.sys.os == cc.sys.OS_IOS) {
    jsb.reflection.callStaticMethod('ABCFileDownloader', 'downloadFileWithUrl:cookie:savePath:', url, cookies, savePath);
} else if(cc.sys.isNative && cc.sys.os == cc.sys.OS_ANDROID) {
    jsb.reflection.callStaticMethod("com/tencent/abcmouse/downloader/ABCFileDownloader", "downloadFileWithUrl", "(Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;)V", url, cookies, savePath);
}

StringBuilder sb = new StringBuilder(JS_STRING_ON_DOWNLOAD_FINISH + "(");
sb.append("'" + success + "',");
sb.append("'" + url + "',");
sb.append("'" + savePath + "',");
sb.append("'" + msg + "',");
sb.append("'" +code + "')");
Cocos2dxJavascriptJavaBridge.evalString(sb.toString());

jsb.fileDownloader.requestDownload(url, savePath, cookies, options, (success, url, savePath, msg, code) => {
    // do whatever you want
});

bool foo(se::State& s)
{
    ...
    ...
}
SE_BIND_FUNC(foo) // 此处以回调函数的定义为例

#define SE_BIND_CTOR(funcName, cls, finalizeCb) \
    void funcName##Registry(const v8::FunctionCallbackInfo<v8::Value>& _v8args) \
    { \
        v8::Isolate* _isolate = _v8args.GetIsolate(); \
        v8::HandleScope _hs(_isolate); \
        bool ret = true; \
        se::ValueArray args; \
        se::internal::jsToSeArgs(_v8args, &args); \
        se::Object* thisObject = se::Object::_createJSObject(cls, _v8args.This()); \
        thisObject->_setFinalizeCallback(_SE(finalizeCb)); \
        se::State state(thisObject, args); \
        ret = funcName(state); \
        if (!ret) { \
            SE_LOGE("[ERROR] Failed to invoke %s, location: %s:%d\n", #funcName, __FILE__, __LINE__); \
        } \
        se::Value _property; \
        bool _found = false; \
        _found = thisObject->getProperty("_ctor", &_property); \
        if (_found) _property.toObject()->call(args, thisObject); \
    }

jsb.fileDownloader.download(url, path, (msg, code) => {
    // do whatever you want
});

class FileDownloader {
        public:
            typedef std::function<void(const std::string& msg, const int code)> ResultCallback;
            static FileDownloader* getInstance();
            static void destroyInstance();
            void download(const std::string& url,
                                         const std::string& savePath,
                                         const ResultCallback& callback);
            void onDownloadResult(const std::string msg, const int code);
            ... ...
        protected:
            static FileDownloader* s_sharedFileDownloader;
            std::unordered_map<std::string, ResultCallback> reqCtx;
};

SE_DECLARE_FUNC(js_cocos2dx_network_FileDownloader_download); // 声明成员函数，下载调用
SE_DECLARE_FUNC(js_cocos2dx_network_FileDownloader_getInstance); // 声明静态函数，获取单例

static bool js_cocos2dx_network_FileDownloader_download(se::State &s) { // 方法名与声明时一致
    // TODO
}

SE_BIND_FUNC(js_cocos2dx_network_FileDownloader_download); // 包装该方法

static bool js_cocos2dx_network_FileDownloader_getInstance(se::State& s) { // 方法名与声明时一致
    // TODO
}

SE_BIND_FUNC(js_cocos2dx_network_FileDownloader_getInstance); // 包装该方法

bool js_register_cocos2dx_network_FileDownloader(se::Object* obj) {
    auto cls = se::Class::create("FileDownloader", obj, nullptr, nullptr);
    cls->defineFunction("download", _SE(js_cocos2dx_network_FileDownloader_download));
    cls->defineStaticFunction("getInstance", _SE(js_cocos2dx_network_FileDownloader_getInstance));
    cls->install();
    JSBClassType::registerClass<cocos2d::network::FileDownloader>(cls);
    se::ScriptEngine::getInstance()->clearException();
    return true;
}

bool register_all_cocos2dx_network(se::Object* obj)
{
    // Get the ns
    se::Value nsVal;
    if (!obj->getProperty("jsb", &nsVal))
    {
        se::HandleObject jsobj(se::Object::createPlainObject());
        nsVal.setObject(jsobj);
        obj->setProperty("jsb", nsVal);
    }
    se::Object* ns = nsVal.toObject();

    ... ...
    // 将前面生成的 Class 注册 设置为 jsb 的一个属性，这样我们便能通过
    // let downloader = new jsb.FileDownloader();
    // 获取实例
    js_register_cocos2dx_network_FileDownloader(ns);
    return true;
}

static bool js_cocos2dx_network_FileDownloader_getInstance(se::State& s)
{
    const auto& args = s.args();
    size_t argc = args.size();
    CC_UNUSED bool ok = true;
    if (argc == 0) {
        cocos2d::network::FileDownloader* result = cocos2d::network::FileDownloader::getInstance(); // C++ 单例
        ok &= native_ptr_to_seval<cocos2d::network::FileDownloader>((cocos2d::network::FileDownloader*)result, &s.rval());
        SE_PRECONDITION2(ok, false, "js_cocos2dx_network_FileDownloader_getInstance : Error processing arguments");
        return true;
    }
    SE_REPORT_ERROR("wrong number of arguments: %d, was expecting %d", (int)argc, 0);
    return false;
}

static bool js_cocos2dx_network_FileDownloader_download(se::State &s) {
    cocos2d::network::FileDownloader *cobj = (cocos2d::network::FileDownloader *) s.nativeThisObject();
    SE_PRECONDITION2(cobj, false,
                     "js_cocos2dx_network_FileDownloader_download : Invalid Native Object");
    const auto &args = s.args();
    size_t argc = args.size();
    CC_UNUSED bool ok = true;
    if (argc == 3) {
        std::string url;
        std::string path;
        ok &= seval_to_std_string(args[0], &url); // 转化为std::string url
        ok &= seval_to_std_string(args[1], &path); // 转化为std::string path
        std::function<void(const std::string& msg,
                           const int code)> callback;
        do {
            if (args[2].isObject() && args[2].toObject()->isFunction())
            {
                se::Value jsThis(s.thisObject());
                // 获取 JS 回调
                se::Value jsFunc(args[2]);
                // 如果目标类是一个单例则不能用 se::Object::attachObject 去关联
                // 必须使用 se::Object::root，无需关心 unroot，unroot 的操作会随着 lambda 的销毁触发 jsFunc 的析构，在 se::Object 的析构函数中进行 unroot 操作。
                // 如果使用 s.thisObject->attachObject(jsFunc.toObject);会导致对应的 func 和 target 永远无法被释放，引发内存泄露。
                jsFunc.toObject()->root(); 
                auto lambda = [=](const std::string& msg,
                                  const int code) -> void {
                    se::ScriptEngine::getInstance()->clearException();
                    se::AutoHandleScope hs;
                    CC_UNUSED bool ok = true;
                    se::ValueArray args;
                    args.resize(2);
                    ok &= std_string_to_seval(msg, &args[0]);
                    ok &= int32_to_seval(code, &args[1]);
                    se::Value rval;
                    se::Object* thisObj = jsThis.isObject() ? jsThis.toObject() : nullptr;
                    se::Object* funcObj = jsFunc.toObject();
                    // 执行 JS 方法回调
                    bool succeed = funcObj->call(args, thisObj, &rval);
                    if (!succeed) {
                        se::ScriptEngine::getInstance()->clearException();
                    }
                };
                callback = lambda;
            }
            else
            {
                callback = nullptr;
            }
        } while(false)
                ;
        SE_PRECONDITION2(ok, false, "js_cocos2dx_network_FileDownloader_download : Error processing arguments");
        cobj->download(url, path, callback);
        return true;
    }
    SE_REPORT_ERROR("wrong number of arguments: %d, was expecting %d", (int) argc, 3);
    return false;
}

// FileDownloader
jsb.fileDownloader = jsb.FileDownloader.getInstance();
delete jsb.FileDownloader;

network::FileDownloader::destroyInstance();