Cocos2dx-jsb 中Node的onEnter过程分析(1)

Cocos2dx-jsb 中Node的onEnter过程分析(1)：
1、
当一个子节点被接入到父节点上时，都会调用Node::addChild方法，
if( _running )
    {
        child->onEnter(); //调用子节点的onEnter方法
        // prevent onEnterTransitionDidFinish to be called twice when a node is added in onEnter
        if (_isTransitionFinished) //如果有场景又过度，则调用onEnterTransitionDidFinish方法，和上面的onEnter方法类似。
        {
            child->onEnterTransitionDidFinish();
        }
    }
2、
onEnter方法分析：
void Node::onEnter()
{
    if (_onEnterCallback) //如果有回到，则调用
        _onEnterCallback();

○1#if CC_ENABLE_SCRIPT_BINDING  //如果绑定了脚本，则调用
    if (_scriptType == kScriptTypeJavascript)
    {
       ○2 if (ScriptEngineManager::sendNodeEventToJS(this,kNodeOnEnter))
            return;
    }
#endif
    
   ○3 _isTransitionFinished = false;
    
    for( const auto &child: _children)
        child->onEnter();
    
    this->resume();
    
    _running = true;
    
#if CC_ENABLE_SCRIPT_BINDING
    if (_scriptType == kScriptTypeLua)
    {
        ScriptEngineManager::sendNodeEventToLua(this,kNodeOnEnter);
    }
#endif
}

3、
看函数的名字，发送节点事件给JS
ScriptEngineManager::sendNodeEventToJS(this,kNodeOnEnter)
bool ScriptEngineManager::sendNodeEventToJS(Node* node,int action)
{
    auto scriptEngine = getInstance()->getScriptEngine();
    //这里是为了防止反复调用，标记是不是从JS调用的
    if (scriptEngine->isCalledFromScript())
    {
        // Should only be invoked at root class Node
        scriptEngine->setCalledFromScript(false);
    }
    else
    {
        BasicScriptData data(node,(void*)&action);
        ScriptEvent scriptEvent(kNodeEvent,(void*)&data);
        if (scriptEngine->sendEvent(&scriptEvent))
            return true;
    }
    
    return false;
}
4、sendEvent： 
int ScriptingCore::sendEvent(ScriptEvent* evt)
{
    if (NULL == evt)
        return 0;
 
    // special type,can't use this code after JSAutoCompartment
    if (evt->type == kRestartGame)
    {
        restartVM();
        return 0;
    }

    JSAutoCompartment ac(_cx,_global.ref().get());
//这里会根据事件的类型调用不同的函数，我们这里的是kNodeEvent事件，
//我们这次只分析这个
    switch (evt->type)
    {
        case kNodeEvent:
            {
                return handleNodeEvent(evt->data);
            }
            break;
        case kMenuClickedEvent:
            break;
        case kTouchEvent:
            {
                TouchScriptData* data = (TouchScriptData*)evt->data;
                return handleTouchEvent(data->nativeObject,data->actionType,data->touch,data->event);
            }
            break;
        case kTouchesEvent:
            {
                TouchesScriptData* data = (TouchesScriptData*)evt->data;
                return handleTouchesEvent(data->nativeObject,data->touches,data->event);
            }
            break;
        case kComponentEvent:
            {
                return handleComponentEvent(evt->data);
            }
            break;
        default:
            CCASSERT(false,"Invalid script event.");
            break;
    }
    
    return 0;
}

5、handleNodeEvent这个函数是真正的调用Js
int ScriptingCore::handleNodeEvent(void* data)
{
    if (NULL == data)
        return 0;
    
    BasicScriptData* basicScriptData = static_cast<BasicScriptData*>(data);
    if (NULL == basicScriptData->nativeObject || NULL == basicScriptData->value)
        return 0;
    
    Node* node = static_cast<Node*>(basicScriptData->nativeObject);
    int action = *((int*)(basicScriptData->value));
                                                         
    js_proxy_t * p = jsb_get_native_proxy(node);
    if (!p) return 0;

    int ret = 0;
    JS::RootedValue retval(_cx);
    jsval dataVal = INT_TO_JSVAL(1);

    if (action == kNodeOnEnter)
{
//根据不同的事件，如果JS又重载，调用不同的JS重载函数。
        if (isFunctionOverridedInJS(JS::RootedObject(_cx,p->obj.get()),"onEnter",js_cocos2dx_Node_onEnter))
        {
            ret = executeFunctionWithOwner(OBJECT_TO_JSVAL(p->obj),1,&dataVal,&retval);
        }
        resumeSchedulesAndActions(p);
    }
    else if (action == kNodeOnExit)
    {
        if (isFunctionOverridedInJS(JS::RootedObject(_cx,"onExit",js_cocos2dx_Node_onExit))
        {
            ret = executeFunctionWithOwner(OBJECT_TO_JSVAL(p->obj),&retval);
        }
        pauseSchedulesAndActions(p);
    }
    else if (action == kNodeOnEnterTransitionDidFinish)
    {
        if (isFunctionOverridedInJS(JS::RootedObject(_cx,"onEnterTransitionDidFinish",js_cocos2dx_Node_onEnterTransitionDidFinish))
        {
            ret = executeFunctionWithOwner(OBJECT_TO_JSVAL(p->obj),&retval);
        }
    }
    else if (action == kNodeOnExitTransitionDidStart)
    {
        if (isFunctionOverridedInJS(JS::RootedObject(_cx,"onExitTransitionDidStart",js_cocos2dx_Node_onExitTransitionDidStart))
        {
            ret = executeFunctionWithOwner(OBJECT_TO_JSVAL(p->obj),&retval);
        }
    }
    else if (action == kNodeOnCleanup) {
        cleanupSchedulesAndActions(p);
    }

    return ret;
}

6、到此为止，○1○2两部分都分析完了，那第○3部分，什么时候调用呢？
第三部分的代码：
   _isTransitionFinished = false;
    
    for( const auto &child: _children)
        child->onEnter();
    
    this->resume();
    
_running = true;
第三部分的其实是在JS中重载的onEnter函数：其实也就是我们的onEnter调用过程的测试代码：
onEnter : function (){
    cc.log("onEnter+++++++++++++++++++++++++2222211")
    this._super(); // 第○3部分是在这里调用的,下一篇再进行分析。
    cc.log("onEnter+++++++++++++++++++++++++2222222")
}

（编辑：李大同）

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