关于Cocos2d-x中UI按钮的定义

1.要有两张不同状态的图片

2.定义一个MenuItemSprite的实例，把这两张图的Sprite实例放进MenuItemSprite的实例

3.把MenuItemSprite的实例放进Menu实例

(4.暂停按钮的这种的要把MenuItemSprite的实例再放进MenuItemToggle实例中，再把MenuItemToggle实例放进Menu实例中)

5.把Menu实例addChild到层

例子

开始游戏按钮

    auto startNormal = Sprite::create("startNormal.png");
    auto startSelected = Sprite::create("startSelected.png");
    auto startSpriteItem = MenuItemSprite::create(startNormal, startSelected, CC_CALLBACK_1(StartUp::menuStartCallback, this));
    auto menu = Menu::create(startSpriteItem, NULL);
    this->addChild(menu);
    menu->setPosition(visibleSize.width / 2, visibleSize.height / 2);

void StartUp::menuStartCallback(Ref* pSender)
{
    //Director::getInstance()->getEventDispatcher()->removeEventListener(touchListener);
    Director::getInstance()->replaceScene(TransitionFade::create(1, GameScene::createScene(1)));
}

暂停按钮

　　//加入暂停按钮
    auto pause_sp1 = Sprite::create("game_pause_nor.png");
    auto pause_sp2 = Sprite::create("game_pause_pressed.png");
    auto resume_sp1 = Sprite::create("game_resume_nor.png");
    auto resume_sp2 = Sprite::create("game_resume_pressed.png");

    auto pauseitem = MenuItemSprite::create(pause_sp1, pause_sp2);
    auto resumeitem = MenuItemSprite::create(resume_sp1, resume_sp2);
    auto pauseButton = MenuItemToggle::createWithTarget(this, menu_selector(GameScene::pauseButtonCallBack), pauseitem, resumeitem, nullptr);
    pauseButton->setAnchorPoint(Vec2(0, 0));
    pauseButton->setPosition(Vec2(size.width / 2 - pauseButton->getContentSize().width, size.height / 2 - pauseButton->getContentSize().height)); //位于左上角

    auto menu = Menu::create(pauseButton, nullptr);
    menu->setScale(0.2);
    addChild(menu, 4, PAUSE_MENU);

void GameScene::pauseButtonCallBack(Ref* pSender)
{
    //log("press pause button!");
}