Cocos2d-x中停止播放背景音乐

停止背景音乐播放代码放置到什么地方比较适合呢？例如：在HelloWorld场景中，主要代码如下：

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bool HelloWorld::init()  
{  
   return true;  
}  
   
void HelloWorld::onEnter()  
{  
    Layer::onEnter();  
    log("HelloWorldonEnter");  
}  
   
voidHelloWorld::onEnterTransitionDidFinish()  
{  
    Layer::onEnterTransitionDidFinish();  
    log("HelloWorldonEnterTransitionDidFinish");          
}  
   
void HelloWorld::onExit()  
{  
    Layer::onExit();  
    log("HelloWorldonExit");  
    //停止播放代码                                                                                                                          ①  
}  
   
voidHelloWorld::onExitTransitionDidStart()  
{  
    Layer::onExitTransitionDidStart();  
    log("HelloWorldonExitTransitionDidStart");       
    //停止播放代码                                                                                                                          ②  
}  
   
void HelloWorld::cleanup()  
{  
    Layer::cleanup();                                                                                                                                
    log("HelloWorldcleanup");  
    //停止播放代码                                                                                                                          ③  
}  