cocos2dx源码分析：场景切换

来源：互联网发布：中国电子科技集团知乎编辑：程序博客网时间：2024/05/21 19:37

cocos2dx的Director管理场景切换，其中有几个和场景相关的成员变量

 /* The running scene */Scene *_runningScene;/*当前正在运行的场景，即渲染中的场景*//* will be the next 'runningScene' in the next framenextScene is a weak reference. */Scene *_nextScene;/*下一帧_nextScene会替换_runningScene*//* scheduled scenes */Vector<Scene*> _scenesStack;/*场景栈*/

程序启动后，使用Director::runWithScene进入第一个Scene，它把scene存储场景栈中，并设置_nextScene，设置_nextScene后，下一帧就可成为_runningScene

void Director::runWithScene(Scene *scene){    CCASSERT(scene != nullptr, "This command can only be used to start the Director. There is already a scene present.");    CCASSERT(_runningScene == nullptr, "_runningScene should be null");    pushScene(scene);    startAnimation();}

void Director::pushScene(Scene *scene){    CCASSERT(scene, "the scene should not null");    _sendCleanupToScene = false;#if CC_ENABLE_GC_FOR_NATIVE_OBJECTS    auto sEngine = ScriptEngineManager::getInstance()->getScriptEngine();    if (sEngine)    {        sEngine->retainScriptObject(this, scene);    }#endif // CC_ENABLE_GC_FOR_NATIVE_OBJECTS    _scenesStack.pushBack(scene);    _nextScene = scene;}

之后如果想再添加新场景有两种方法，
1. 使用pushScene覆盖在当前场景之上，此时当前场景并未被销毁，当覆盖在其之上的场景销毁时，此场景可以继续运行；
2. 使用replaceScene替换当前场景，当前场景数据在下一帧会被销毁，无法恢复。

void Director::replaceScene(Scene *scene){    //CCASSERT(_runningScene, "Use runWithScene: instead to start the director");    CCASSERT(scene != nullptr, "the scene should not be null");    if (_runningScene == nullptr) {        runWithScene(scene);        return;    }    if (scene == _nextScene)        return;    if (_nextScene)    {        if (_nextScene->isRunning())        {            _nextScene->onExit();        }        _nextScene->cleanup();        _nextScene = nullptr;    }    ssize_t index = _scenesStack.size() - 1;    _sendCleanupToScene = true;#if CC_ENABLE_GC_FOR_NATIVE_OBJECTS    auto sEngine = ScriptEngineManager::getInstance()->getScriptEngine();    if (sEngine)    {        sEngine->retainScriptObject(this, scene);        sEngine->releaseScriptObject(this, _scenesStack.at(index));    }#endif // CC_ENABLE_GC_FOR_NATIVE_OBJECTS    /*直接替换了栈上的当前场景，当前场景在下一帧会被销毁*/    _scenesStack.replace(index, scene);    _nextScene = scene;}

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