CCScene* HelloWorld::scene()
{
    CCScene * scene = NULL;
    do
    {
        // 'scene' is an autorelease object 创建一个空场景
        scene = CCScene::create();
        CC_BREAK_IF(! scene);

        // 'layer' is an autorelease object 创建一个层
        HelloWorld *layer = HelloWorld::create();
        CC_BREAK_IF(! layer);

        // add layer as a child to scene
               // 把层添加到场景中。
               // 只有放置到已经呈现出来的游戏元素中，它才会呈现出来
        scene->addChild(layer);
    } while (0);

    // return the scene
    return scene;
}

// on "init" you need to initialize your instance
bool HelloWorld::init()
{
    bool bRet = false ;
    do
    {
        //
        // super init first
        //

        CC_BREAK_IF(! CCLayer::init());//调用父类的init方法进行最初的初始化

        //
        // add your codes below...
        //

        // 1. Add a menu item with "X" image, which is clicked to quit the program.

        // Create a "close" menu item with close icon, it's an auto release object.
        // 创建菜单并添加到层
        CCMenuItemImage *pCloseItem = CCMenuItemImage::create(
            "CloseNormal.png" ,
            "CloseSelected.png" ,
            this,
            menu_selector(HelloWorld::menuCloseCallback));
        CC_BREAK_IF(! pCloseItem);

        // Place the menu item bottom-right conner.
        pCloseItem->setPosition(ccp(CCDirector::sharedDirector()->getWinSize().width - 20, 20));

        // Create a menu with the "close" menu item, it's an auto release object.
        CCMenu* pMenu = CCMenu::create(pCloseItem, NULL);
        pMenu->setPosition(CCPointZero);
        CC_BREAK_IF(! pMenu);

        // Add the menu to HelloWorld layer as a child layer.
        this->addChild(pMenu, 1);

        // 2. Add a label shows "Hello World".

        // Create a label and initialize with string "Hello World".
        // 创建"Hello World"文本标签并添加到层中
        CCLabelTTF* pLabel = CCLabelTTF::create( "Hello World" , "Arial" , 24);
        CC_BREAK_IF(! pLabel);

        // Get window size and place the label upper.
        CCSize size = CCDirector::sharedDirector()->getWinSize();
        pLabel->setPosition(ccp(size.width / 2, size.height - 50));

        // Add the label to HelloWorld layer as a child layer.
        this->addChild(pLabel, 1);

        // 3. Add add a splash screen, show the cocos2d splash image.
        // 创建显示"HelloWorld.png"的精灵并添加到层中
        CCSprite* pSprite = CCSprite::create( "HelloWorld.png" );
        CC_BREAK_IF(! pSprite);

        // Place the sprite on the center of the screen
        pSprite->setPosition(ccp(size.width/2, size.height/2));

        // Add the sprite to HelloWorld layer as a child layer.
        //void CCNode::addChild(CCNode *child, int zOrder)
        //zOrder指child的z轴顺序，值越大，表示显示位置越靠前
        this->addChild(pSprite, 0);

        bRet = true;
    } while (0);

    return bRet;
}