![\"LibGDX](\"http:\/\/www.pixnbgames.com\/blog\/wp-content\/uploads\/2014\/11\/LibGDX-Screen-Management.png\")
<\/a><\/p>\nMain class of the game<\/h2>\n
At project creation, the main class is called\u00a0 By this, our main game class will be like this:<\/p>\n We will go back to this class later.<\/p>\n To work with class We have said that our game will consist of three screens. These will have the following constructors:<\/p>\n I will not show the implementation of these classes in order to not do this article so long with code that is not related with the main target of this post. In any case, at the end of this article you can see the link to download the source code used in this example.<\/p>\n <\/p>\n In order to know the available scenes, we create\u00a0an\u00a0Enum java type, called\u00a0 If we want to obtain, for example, the screen of main menu we can do this:<\/p>\n <\/p>\n The class\u00a0 <\/p>\n Once exposed classes\u00a0 Here, we simply\u00a0initialize the\u00a0 <\/p>\n To change between screens we only need to call method\u00a0 <\/p>\n You can download the source code from my GitHub<\/a> repository. By executing the program, we can surf through the three screens of the game:<\/p>\n I hope this article is helpful for you. Good luck for your projects and regards.<\/p>\n","protected":false},"excerpt":{"rendered":" When making games, it is common that our application has multiple screens or scenes. Below I will show a way to manage the different scenes in libgdx. For this example, I will supose the game has three screens: the main Seguir leyendo How to manage screens in LibGDX<\/span>MyGdxGame<\/code>\u00a0by default, and it extends from AplicationListener<\/code>. LibGDX has a subclass of AplicationListener<\/code>, the class Game<\/code>, prepared to show \u00a0an implementation of the interface Screen<\/code> at each time.\u00a0That we do is to use the class Game<\/code> as parent of our main class, and each of the screens will be an implementation of Screen<\/code>.<\/p>\npublic class MyGdxGame extends Game {\r\n...\r\n}<\/pre>\nGame Screens<\/h2>\n
Game<\/code>, each screen of our game has to implement the interface Screen<\/code>. Furthermore, I work normaly with class Stage<\/code>. To combine this two elements I use an abstract class, AbstractScreen<\/code>, that extends Stage<\/code> class and implements Screen<\/code> interface. This own class will be the parent class of our screens.<\/p>\npublic abstract class AbstractScreen extends Stage implements Screen {\r\n \r\n protected AbstractScreen() {\r\n super( new StretchViewport(320.0f, 240.0f, new OrthographicCamera()) );\r\n }\r\n \r\n \/\/ Subclasses must load actors in this method\r\n public abstract void buildStage();\r\n\r\n @Override\r\n public void render(float delta) {\r\n \/\/ Clear screen\r\n Gdx.gl.glClearColor(1, 0, 0, 1);\r\n Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);\r\n \r\n \/\/ Calling to Stage methods\r\n super.act(delta);\r\n super.draw();\r\n }\r\n\r\n @Override\r\n public void show() {\r\n Gdx.input.setInputProcessor(this);\r\n }\r\n\r\n @Override\r\n public void resize(int width, int height) {\r\n getViewport().update(width, height, true);\r\n }\r\n\r\n @Override public void hide() {}\r\n @Override public void pause() {}\r\n @Override public void resume() {}\r\n}<\/pre>\nKey issues<\/h3>\n
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buildStage()<\/code>, that will must be implemented by every screen of our game. This method is used to add actors to the scene (LibGDX Scene2d<\/a>).<\/li>\n<\/ul>\n\n
public MainMenuScreen() {...}<\/pre>\n<\/li>\npublic LevelSelectScreen() {...}<\/pre>\n<\/li>\n
\nCommonly we use the same class for several (or all) levels of our game. To know which is the current level, we have a parameter in the class constructor indicating the level:<\/p>\npublic GameScreen(Integer level) {...}<\/pre>\n<\/li>\n<\/ul>\nScreenEnum:\u00a0list of available screens<\/h2>\n
ScreenEnum<\/code>, with the list of possible screens. This enum defines an abstract method\u00a0getScreen()<\/code>\u00a0that allow us to get an screen instance of each enum type.<\/p>\npublic enum ScreenEnum {\r\n\r\n MAIN_MENU {\r\n public AbstractScreen getScreen(Object... params) {\r\n return new MainMenuScreen();\r\n }\r\n },\r\n LEVEL_SELECT {\r\n public AbstractScreen getScreen(Object... params) {\r\n return new LevelSelectScreen();\r\n }\r\n },\r\n GAME {\r\n public AbstractScreen getScreen(Object... params) {\r\n return new GameScreen((Integer) params[0]);\r\n }\r\n };\r\n\r\n publicabstract AbstractScreen getScreen(Object... params);\r\n}<\/pre>\nKey issues<\/h3>\n
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getScreen()<\/code>) for\u00a0get an instance of each screen from its enum type.\u00a0This method supports one variable argument (Object... params<\/code>); this allow to pass params to the screen constructors when it is needed.<\/li>\nMainMenuScreen<\/code>\u00a0and\u00a0LevelSelectScreen<\/code>\u00a0don’t need parameters.<\/li>\nGameScreen<\/code>, in change, need an argument of type Integer<\/code>. So, for instantiate\u00a0this screen we make casting to Integer<\/code> from the first element of the array\u00a0Object... params<\/code>.<\/li>\n<\/ul>\nUsage<\/h3>\n
AbstractScreen mainMenuScreen = ScreenEnum.MAIN_MENU.getScreen();<\/pre>\n
Scenes manager<\/h2>\n
ScreenManager<\/code>\u00a0is the responsible of screens management. This class, in combination with\u00a0ScreenEnum<\/code>, will allow us to change the visible screen in a really easy way:<\/p>\npublic class ScreenManager {\r\n\r\n\u00a0 \u00a0\u00a0\/\/ Singleton: unique instance\r\n\u00a0 \u00a0\u00a0private static ScreenManager instance;\r\n\r\n\u00a0 \u00a0\u00a0\/\/ Reference to game\r\n\u00a0 \u00a0\u00a0private Game game;\r\n\r\n\u00a0 \u00a0\u00a0\/\/ Singleton: private constructor\r\n\u00a0 \u00a0\u00a0private ScreenManager() {\r\n\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0super();\r\n\u00a0 \u00a0\u00a0}\r\n\r\n\u00a0 \u00a0\u00a0\/\/ Singleton: retrieve instance\r\n\u00a0 \u00a0\u00a0public static ScreenManager getInstance() {\r\n\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0if (instance == null) {\r\n\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0instance = new ScreenManager();\r\n\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0}\r\n\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0return instance;\r\n\u00a0 \u00a0\u00a0}\r\n\r\n\u00a0 \u00a0\u00a0\/\/ Initialization with the game class\r\n\u00a0 \u00a0\u00a0public void initialize(Game game) {\r\n\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0this.game = game;\r\n\u00a0 \u00a0\u00a0}\r\n\r\n\u00a0 \u00a0\u00a0\/\/ Show in the game the screen which enum type is received\r\n\u00a0 \u00a0\u00a0public void showScreen(ScreenEnum screenEnum, Object... params) {\r\n\r\n\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\/\/ Get current screen to dispose it\r\n\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0Screen currentScreen = game.getScreen();\r\n\r\n\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\/\/ Show new screen\r\n\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0AbstractScreen newScreen = screenEnum.getScreen(params);\r\n\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0newScreen.buildStage();\r\n\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0game.setScreen(newScreen);\r\n\r\n\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\/\/ Dispose previous screen\r\n\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0if (currentScreen != null) {\r\n\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0currentScreen.dispose();\r\n\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0}\r\n\u00a0 \u00a0\u00a0}\r\n}<\/pre>\nKey issues<\/h3>\n
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ScreenManager.getInstance()<\/pre>\n<\/li>\n
Game<\/code>). We pass this reference in the method\u00a0initialize()<\/code>:\nScreenManager.getInstance().initialize(gameInstance);<\/pre>\n<\/li>\n
showScreen()<\/code>\u00a0allow us to show any screen of the of the game by passing its enum type. We also can pass other params\u00a0needed in the screen constructor. For example:\nScreenManager.getInstance().showScreen( ScreenEnum.LEVEL_SELECT );\r\nScreenManager.getInstance().showScreen( ScreenEnum.GAME, level);<\/pre>\n<\/li>\n<\/ul>\n
Return to main class of the game<\/h2>\n
ScreenEnum<\/code>\u00a0and\u00a0ScreenManager<\/code>, it’s shown the implementation of the main class of the game:<\/p>\npublic class MyGdxGame extends Game {\r\n @Override\r\n publicvoid create () {\r\n ScreenManager.getInstance().initialize(this);\r\n ScreenManager.getInstance().showScreen( ScreenEnum.MAIN_MENU );\r\n }\r\n}<\/pre>\nScreenManager<\/code>\u00a0and we show the main menu screen.<\/p>\nChange Screen<\/h2>\n
showScreen()<\/code>\u00a0of the class\u00a0ScreenManager<\/code>. For example, if we want to go from main menu screen to select level screen, we can use below listener in a button:<\/p>\nbtnPlay.addListener(\r\n new InputListener() {\r\n @Override\r\n public boolean touchDown(InputEvent event,\r\n float x, float y, int pointer, int button) {\r\n ScreenManager.getInstance().showScreen( ScreenEnum.LEVEL_SELECT );\r\n return false;\r\n }\r\n });<\/pre>\nSource code<\/h2>\n
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