Cocos2xd__场景(层)的生命周期

生命周期函数：

1. bool init()：初始化场景时调用

2. void onEnter()：进入场景时调用

3. void onEnterTransitionDidFinish()：进入场景且过度动画结束时调用

4. void onExit()：退出场景时调用

5. void onExitTransitionDidStart()：退出场景且开始过度动画时调用

6. void cleanup()：场景对象被清除时调用

如：

virtual void onEnter() override
{
    Scene::onEnter();
    cocos2d::log("...TestScene onEnter...");
}
virtual void onEnterTransitionDidFinish() override
{
    Scene::onEnterTransitionDidFinish();
    cocos2d::log("...TestScene onEnterTransitionDidFinish...");
}
virtual void onExit() override
{
    Scene::onExit();
    cocos2d::log("...TestScene onExit...");
}
virtual void onExitTransitionDidStart() override
{
    Scene::onExitTransitionDidStart();
    cocos2d::log("...TestScene onExitTransitionDidStart...");
}
virtual void cleanup() override
{
    Scene::cleanup();
    cocos2d::log("...TestScene cleanup...");
}