1. 首先在头文件中定义一个Sprite指针s和一个float变量ry，重载update函数：

public:
    ...
    virtual void update(float dt);
    ...

private:
    float ry;
    cocos2d::Sprite * s;

1. 然后将init函数的实现改为：

// on "init" you need to initialize your instance
bool HelloWorld::init()
{
    //////////////////////////////
    // 1. super init first
    if ( !Layer::init() )
    {
        return false;
    }

    ry = 0;
    Size visibleSize = Director::getInstance()->getVisibleSize();

    s = Sprite::create("HelloWorld.png");
    s->setAnchorPoint(Vec2(0,0.5f));
    s->setPosition(visibleSize.width / 2,visibleSize.height / 2);
    addChild(s);

    scheduleUpdate();

    return true;
}

void HelloWorld::update(float dt){
    //s->setPositionZ(s->getPositionZ() + 1);

    ry++;
    s->setRotation3D(Vec3(0,ry,0));
}