Your First Game – Air Hockey - Cocos2d-x by Example Beginner's Guide - page 74

Time for action - implementing init()
Inside init() , we'll build the game screen, bringing in all the sprites and labels we'll
need for the game:
1. So right after the if statement where we call the super Layer::init method,
we add:
_players = Vector<GameSprite*>(2);
_player1Score = 0;
_player2Score = 0;
_screenSize = Director::getInstance()->getWinSize();
2. We create the vector where we'll store both players, initialize the score values, and
grab the screen size from the singleton, all-knowing Director . We'll use the
screen size to position all sprites relatively. Next we will create our first sprite. It is
created with an image filename, which FileUtils will take care of loading from
the correct folder:
auto court = Sprite::create("court.png");
court->setPosition(Vec2(_screenSize.width * 0.5,
_screenSize.height * 0.5));
this->addChild(court);
3. Get into the habit of positioning sprites with relative values, and not absolute ones,
so we can support more screen sizes. And say hello to the Vec2 type definition
used to create points; you'll be seeing it a lot in Cocos2d-x.
4. We finish by adding the sprite as a child to our GameLayer (the court sprite does
not need to be a GameSprite ).
5. Next we will use our spanking new GameSprite class, carefully positioning the
objects on screen:
_player1 =
GameSprite::gameSpriteWithFile("mallet.png");
_player1->setPosition(Vec2(_screenSize.width * 0.5,
_player1->radius() * 2));
_players.pushBack(_player1);
this->addChild(_player1);