cocos2d-x button setTitleLabel

    string file("res/Button.png");
    auto btn = cocos2d::ui::Button::create(file, file, file);
    btn->setColor(Color3B(24, 48, 64));
    btn->setPosition(display / 2);
    btn->setPressedActionEnabled(true);
    btn->setContentSize(Size(200, 100));

    btn->setTitleLabel(Label::createWithTTF("","fonts/arial.ttf",30));

    btn->setTitleColor(Color3B::BLUE);

    btn->setTitleText("Musics");
    btn->setTitleFontSize(30);
    btn->setName("Music");
    btn->addClickEventListener(std::bind(&FirstScene::OnCallback, this, std::placeholders::_1));
    this->addChild(btn);

//需要在设置title之前改变节点