载入场景的目的是预加载资源，也就是在场景进入时，把资源加载到内存中：

// 重写onEnter方法，场景载入时，会调用此方法，此外我们还需要调一下父类的方法，这个是API说明的，照做就行。
// 方法其实功能是很简单的，就是先显示一张splash图片，然后异步加载图片资源，这个addImageAsync方法是引擎内部提供的API，可异步加载，这样就不会阻塞主线程了。
void LoadingScene::onEnter() {
  Layer::onEnter();

  // Add the splash screen image
  auto background = Sprite::create("splash.png");
  auto size = Director::getInstance()->getVisibleSize();
  auto origin = Director::getInstance()->getVisibleOrigin();

  background->setPosition(origin.x + size.width / 2,origin.y + size.height / 2);
  this->addChild(background);

  // Start to load texture async
  auto texture = Director::getInstance()->getTextureCache();
  texture->addImageAsync("atlas.png",CC_CALLBACK_1(LoadingScene::onLoadFinishedCallback,this));
}

加载完成后，就是加载音频文件，这里是同步加载的，如果资源很多的话，会卡的。加载完成后，就进入到WelcomeScene了。

void LoadingScene::onLoadFinishedCallback(cocos2d::Texture2D *texture) {
  // Load the atlas
  AtlasLoader::getInstance()->loadAtlas("atlas.txt",texture);

  // Preload effect music.
  // Here is not the best way to load all music files,
  // in real projects,you should find a better way to do.
  CocosDenshion::SimpleAudioEngine::getInstance()->preloadEffect("sfx_die.ogg");
  CocosDenshion::SimpleAudioEngine::getInstance()->preloadEffect("sfx_hit.ogg");
  CocosDenshion::SimpleAudioEngine::getInstance()->preloadEffect("sfx_point.ogg");
  CocosDenshion::SimpleAudioEngine::getInstance()->preloadEffect("sfx_swooshing.ogg");
  CocosDenshion::SimpleAudioEngine::getInstance()->preloadEffect("sfx_wing.ogg");

  // Now the task of the loading scene has finished,
  // auto enter into the welcome scene
  auto scene = TransitionFade::create(1.0f,WelcomeScene::createScene());
  Director::getInstance()->replaceScene(scene);
}

下一步：说说欢迎场景