Cocos2d-X循环背景效果

HelloWorld::bd(0, 0, 98);
HelloWorld::bd(0, 2130, 99);
this->schedule(schedule_selector(HelloWorld::move));

void HelloWorld::bd(float num, int w, int tag)
{
    CCPoint origin = CCDirector::sharedDirector()->getVisibleOrigin();
    CCSize size = CCDirector::sharedDirector()->getWinSize();
    float x = size.width, y = size.height + origin.y;

    CCSprite *background = CCSprite::create("bg.png");
    background->setAnchorPoint(CCPoint(0, 0.5));
    background->setPosition(CCPoint(background->getContentSize().width*num + w, y / 2));
    this->addChild(background, tag, tag);
}

void HelloWorld::move(float time)
{
    CCPoint origin = CCDirector::sharedDirector()->getVisibleOrigin();
    CCSize size = CCDirector::sharedDirector()->getWinSize();
    float x = size.width, y = size.height + origin.y;

    CCNode *bg1 = CCNode::getChildByTag(99);
    CCSprite *sp1 = (CCSprite*)bg1;

    CCNode *bg2 = CCNode::getChildByTag(98);
    CCSprite *sp2 = (CCSprite*)bg2;

    sp1->setPosition(CCPoint(sp1->getPositionX() - 0.5, sp1->getPositionY()));
    sp2->setPosition(CCPoint(sp2->getPositionX() - 0.5, sp2->getPositionY()));
    if (sp1->getPositionX() <= -sp1->getContentSize().width) sp1->setPosition(CCPoint(sp1->getContentSize().width, y / 2));
    if (sp2->getPositionX() <= -sp2->getContentSize().width) sp2->setPosition(CCPoint(sp2->getContentSize().width, y / 2));
}