这一节我们来具体说说Scene，简单来说Scene就是一个容器，其中可以容纳Sprite、Label、Node等各种游戏中需要的对象。Scene还负责控制游戏的逻辑和内部对象的渲染，游戏中至少有一个Scene，也可以有多个Scene互相切换，并且在Scene切换的过程中还可以指定炫酷的效果。下面的代码创建了一个Scene
auto dirs = Director::getInstance();
Size visibleSize = dirs->getVisibleSize();
Vec2 origin = dirs->getVisibleOrigin();
scene1 = Scene::create();
auto nodeItems = Node::create();
nodeItems->setName("nodeItems");
auto menuNode = Node::create();
menuNode->setName("menuNode");
int index = 2;
auto thisSceneLabel = Label::createWithTTF("This Is A Scene","Marker Felt.ttf",32);
thisSceneLabel->setPosition(Vec2(visibleSize.width / 2,visibleSize.height / 2));
scene1->addChild(thisSceneLabel,1);
auto menuItem1 = MenuItemFont::create("Make A New Scene");
menuItem1->setFontNameObj("Marker Felt.ttf");
menuItem1->setFontSizeObj(32);
menuItem1->setName("menuItem1");
menuItem1->setPosition(Vec2(origin.x + visibleSize.width / 2,origin.y + visibleSize.height / 2).x,(Vec2(origin.x + visibleSize.width / 2,origin.y + visibleSize.height).y - (index) * 40));
menuItem1->setCallback([&](cocos2d::Ref *sender) {
Director::getInstance()->replaceScene(createScene2());
});
auto menu = Menu::create(menuItem1,NULL);
menu->setName("menu");
menuNode->addChild(menu,1);
menu->setPosition(Vec2::ZERO);
scene1->addChild(menuNode,2);
创建结果如下
第24、25、26行设置了菜单的回调函数，当点击菜单时就会执行替换Scene的操作。replaceScene函数用于直接替换Scene，不添加任何效果。替换效果如下
创建这个Scene的代码如下
auto dirs = Director::getInstance();
Size visibleSize = dirs->getVisibleSize();
Vec2 origin = dirs->getVisibleOrigin();
scene2 = Scene::create();
scene2->retain();
auto nodeItems = Node::create();
nodeItems->setName("nodeItems");
auto menuNode = Node::create();
menuNode->setName("menuNode");
int index = 2;
auto thisSceneLabel = Label::createWithTTF("This Is A New Scene",visibleSize.height / 2));
scene2->addChild(thisSceneLabel,1);
auto menuItem1 = MenuItemFont::create("Make a New Scene Using a Transition Fade");
menuItem1->setFontNameObj("Marker Felt.ttf");
menuItem1->setFontSizeObj(32);
menuItem1->setName("menuItem1");
menuItem1->setPosition(Vec2(origin.x + visibleSize.width / 2,origin.y + visibleSize.height).y - (index)* 40));
menuItem1->setCallback([&](cocos2d::Ref *sender) {
Director::getInstance()->replaceScene(TransitionFade::create(0.5,createScene3(),Color3B(0,255,255)));
});
auto menu = Menu::create(menuItem1,1);
menu->setPosition(Vec2::ZERO);
scene2->addChild(menuNode,2);
return scene2;
注意27行菜单回调函数的内容，这里使用了TransitionFade::create来创建了一个0.5秒长的渐变褪色效果，点击菜单效果如下
创建这个Scene的代码如下
auto dirs = Director::getInstance();
Size visibleSize = dirs->getVisibleSize();
Vec2 origin = dirs->getVisibleOrigin();
scene3 = Scene::create();
scene3->retain();
auto nodeItems = Node::create();
nodeItems->setName("nodeItems");
auto menuNode = Node::create();
menuNode->setName("menuNode");
int index = 2;
auto thisSceneLabel = Label::createWithTTF("This Scene used a Transition!",visibleSize.height / 2));
scene3->addChild(thisSceneLabel,1);
auto menuItem1 = MenuItemFont::create("Make a New Scene Using a Flip");
menuItem1->setFontNameObj("Marker Felt.ttf");
menuItem1->setFontSizeObj(32);
menuItem1->setName("menuItem1");
menuItem1->setPosition(Vec2(origin.x + visibleSize.width / 2,origin.y + visibleSize.height).y - (index)* 40));
menuItem1->setCallback([&](cocos2d::Ref *sender) {
Director::getInstance()->replaceScene(TransitionFlipX::create(2,createScene4()));
});
auto menu = Menu::create(menuItem1,1);
menu->setPosition(Vec2::ZERO);
scene3->addChild(menuNode,2);
return scene3;
在27行的菜单回调函数中使用TransitionFlipX::create函数创建了一个2秒的翻转效果，点击菜单执行效果如下
除了上面介绍的3种切换Scene的方法，还有如下方法来用于切换Scene。
TransitionSlideInT::create用来创上下欢动切换效果。
pushScene用于把已经存在的Scene放到场景堆栈中，之后可以用popScene把场景堆栈中的Scene取出。
下一节我们将讲述其它和UI有关的部分。
