cocos2d-x的CCDirector::replaceScene(CCScene *pScene) 使用注意

昨晚在捕鱼切换场景时发现会出现内存不足的现象，看了下代码发现了个问题。我们先看看代码

[[CCDirector sharedDirector] runWithScene:[ SceneA scene]];
[[CCDirector sharedDirector] replaceScene:[ SceneB scene]];

假设CCDirector以SceneA为起始场景，现在要替换为SceneB。那么：

将会触发一系列的方法被调用，如下：
1. scene:<wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; line-height:22px"><wbr></wbr></span><span style="word-wrap:normal; word-break:normal; line-height:22px"><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></span></wbr></wbr></wbr></wbr>SceneB
2. init:<wbr><wbr><wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; line-height:22px"><wbr></wbr></span><span style="word-wrap:normal; word-break:normal; line-height:22px"><wbr></wbr></span><span style="word-wrap:normal; word-break:normal; line-height:22px"><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></span></wbr></wbr></wbr></wbr></wbr></wbr>SceneB
3. onEnter:<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>SceneB
4. Transition发生.
5. onExit:<wbr><wbr><span style="word-wrap:normal; word-break:normal; line-height:22px"><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></span><span style="word-wrap:normal; word-break:normal; line-height:22px"><wbr></wbr></span></wbr></wbr>SceneA
6. onEnterTransitionDidFini<wbr><wbr>sh:</wbr></wbr><wbr>SceneB</wbr>

7. dealloc:<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>SceneB

<wbr></wbr>

当一个scene被搬上“台面”，它会收到onEnter，SceneB会收到onExit，最后交替完成在台面上的SceneA收到onEnterTransitionDidFini<wbr><wbr>sh</wbr></wbr>。从中我们可以看出，只有当登台的SceneA完全加载完成，下场的SceneB才会被释放。两个scene在某一帧是同时处在内存里的，内存自然会表示压力山大。

再看看cocos2d-x的源代码

void CCDirector::replaceScene(CCScene *pScene)
{
       assert(pScene != NULL);
 
       unsigned int index = m_pobScenesStack->count();
 
       m_bSendCleanupToScene = true;
       m_pobScenesStack->replaceObjectAtIndex(index - 1, pScene);
 
       m_pNextScene = pScene;
 // replaceScene赋值m_pNextScene，以致drawScene会触发setNextScene函数。
}
 
void CCDirector::setNextScene(void)
｛
       ···;
       if (! (newSceneType & ccTransitionScene))
       {
         if (m_pRunningScene)
         {
           m_pRunningScene->onExit(); //即 5. onExit:    SceneA
         }    
       }
         ···;
}

释放一些new出来的对象，应该在onExit()里面delete掉。之前不知道原理，new出来的对象在destroy()里面delete，结果就是运行时弹窗口了…