Switch between Libgdx screens

Question

Hi everyone, I'm still working on this libgdx project, and I'm trying to find a better way to change the screens on the screen of my game. Now that the button is pressed, I need it to go to the game screen. I have seen several implementations extending the class of the game, but I'm not sure if the best approach is from here. If you see any code that can be improved, let me know.

Here is the main class of the application:

public class ConnectFourApplication implements ApplicationListener { private Screen screen; public static void main(String[] args) { new LwjglApplication(new ConnectFourApplication(), "PennyPop", 1280, 720, true); } @Override public void create() { screen = new MainScreen(); screen.show(); } @Override public void dispose() { screen.hide(); screen.dispose(); } /** Clears the screen with a white color */ private void clearWhite() { Gdx.gl.glClearColor(1, 1, 1, 1); Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT); } @Override public void pause() { screen.pause(); } @Override public void render() { clearWhite(); screen.render(Gdx.graphics.getDeltaTime()); } @Override public void resize(int width, int height) { screen.resize(width, height); } @Override public void resume() { screen.resume(); } } public class MainScreen implements Screen { private final Stage stage; private final SpriteBatch spriteBatch; //Parameter for drawing the buttons private final BitmapFont font; private final TextureAtlas buttons; private final Button SFXButton; private final Button APIButton; private final Button GameButton; private final Skin images; //Parameter for Sound private final com.badlogic.gdx.audio.Sound SFXClick; //Parameter for the api call private final String WeatherUrl; private final HttpRequest request; private final City SanFrancisco; //The screen to load after the game button is hit private Screen gamescreen; public MainScreen() { //Set up our assets spriteBatch = new SpriteBatch(); stage = new Stage(Gdx.graphics.getWidth(), Gdx.graphics.getHeight(), false, spriteBatch); font = new BitmapFont(Gdx.files.internal("assets/font.fnt"), Gdx.files.internal("assets/font.png"), false); buttons = new TextureAtlas("assets/GameButtons.pack"); images = new Skin(buttons); images.addRegions(buttons); SFXButton = new Button(images.getDrawable("sfxButton")); SFXButton.setPosition(295, 310); APIButton = new Button(images.getDrawable("apiButton")); APIButton.setPosition(405, 310); GameButton = new Button(images.getDrawable("gameButton")); GameButton.setPosition(515, 310); SFXClick = Gdx.audio.newSound(Gdx.files.internal("assets/button_click.wav")); //Add our actors to the stage stage.addActor(SFXButton); stage.addActor(APIButton); stage.addActor(GameButton); //Set up our Url request to be used when clicking the button WeatherUrl = "http://api.openweathermap.org/data/2.5/weather?q=San%20Francisco,US"; request = new HttpRequest(HttpMethods.GET); request.setUrl(WeatherUrl); SanFrancisco = new City("Unavailable","Unavailable","0","0"); //init san fran to be displayed before they have clicked the button //initialize the game screen that we will switch to when the button is pressed gamescreen = new GameScreen(); } @Override public void dispose() { spriteBatch.dispose(); stage.dispose(); } @Override public void render(float delta) { stage.act(delta); stage.draw(); //Begin sprite batch spriteBatch.begin(); //Set our on click listeners for our buttons if (SFXButton.isPressed()) SFXClick.play(); if(APIButton.isPressed()) { CallApi(); } if(GameButton.isPressed()) LoadGame(); //Set font color and render the screen font.setColor(Color.RED); font.draw(spriteBatch, "PennyPop", 455 - font.getBounds("PennpyPop").width/2, 460 + font.getBounds("PennyPop").height/2); font.setColor(Color.BLACK); font.draw(spriteBatch, "Current Weather", 900 - font.getBounds("PennpyPop").width/2, 460 + font.getBounds("PennyPop").height/2); font.setColor(Color.LIGHT_GRAY); font.draw(spriteBatch, SanFrancisco.Name, 940 - font.getBounds("PennpyPop").width/2, 420 + font.getBounds("PennyPop").height/2); font.setColor(Color.RED); font.draw(spriteBatch, SanFrancisco.CurrentCondition, 950 - font.getBounds("PennpyPop").width/2, 300 + font.getBounds("PennyPop").height/2); font.draw(spriteBatch, SanFrancisco.Temperature + " Degrees,", 920 - font.getBounds("PennpyPop").width/2, 270 + font.getBounds("PennyPop").height/2); font.draw(spriteBatch, SanFrancisco.WindSpeed, 1200 - font.getBounds("PennpyPop").width/2, 270 + font.getBounds("PennyPop").height/2); //End or sprite batch spriteBatch.end(); } //Handles calling our API public void CallApi(){ //Sends our stored HTTPRequest object Gdx.net.sendHttpRequest(request, new HttpResponseListener() { @Override public void handleHttpResponse(HttpResponse httpResponse) { //Uses our private response reader object to give us a the JSON from the api call JSONObject json = HttpResponseReader(httpResponse); //Gets the name of the city SanFrancisco.Name = (String) json.get("name"); //Parsed through our returned JSON for the weather key JSONArray WeatherArray = (JSONArray) json.get("weather"); //Gets the actual weather dictionary JSONObject Weather = (JSONObject) WeatherArray.get(0); //Finally get the value with the key of description and assign it //To the San Fran current conditions field SanFrancisco.CurrentCondition = (String) Weather.get("description"); //Gets the actual main dictionary JSONObject main = (JSONObject) json.get("main"); //Finally get the values based on the keys SanFrancisco.Temperature = (String) Double.toString((double) main.get("temp")); //Finally get the wind speed JSONObject wind = (JSONObject) json.get("wind"); SanFrancisco.WindSpeed = (String) Double.toString((double) wind.get("speed")); } @Override public void failed(Throwable t) { Gdx.app.log("Failed ", t.getMessage()); } }); } //When the button game button is clicked should load the connect four game public void LoadGame(){ hide(); gamescreen.show(); } //Converts our HttpResponse into a JSON OBject private static JSONObject HttpResponseReader(HttpResponse httpResponse){ BufferedReader read = new BufferedReader(new InputStreamReader(httpResponse.getResultAsStream())); StringBuffer result = new StringBuffer(); String line = ""; try { while ((line = read.readLine()) != null) { result.append(line); } JSONObject json; try { json = (JSONObject)new JSONParser().parse(result.toString()); return json; } catch (ParseException e) { e.printStackTrace(); } } catch (IOException e) { e.printStackTrace(); } return null; } @Override public void resize(int width, int height) { stage.setViewport(width, height, false); } @Override public void hide() { Gdx.input.setInputProcessor(null); } @Override public void show() { Gdx.input.setInputProcessor(stage); render(0); } @Override public void pause() { // Irrelevant on desktop, ignore this } @Override public void resume() { // Irrelevant on desktop, ignore this } } 

Answer 1

This is how I always implement screen shielding:

First, the main class should extend Game (From com.badlogic.gdx.Game ), and you will need to have a new field of type Game :

 public class ConnectFourApplication extends Game{ private Game game; 

Now initialize the Game in the constructor:

 public ConnectFourApplication(){ game = this; // Since this class extends Game 

To set the screen on MainScreen , now all you have to do is use the setScreen(new MainScreen(game)); method setScreen(new MainScreen(game)); (passing Game so that we can set screens from the MainScreen class) Now you need a new constructor for the MainScreen class and a new field:

 private Game game; public MainScreen(Game game){ this.game = game; 

Now you can use game.setScreen(new Screen(game)); to set the screen to another class that implements Screen .

But now, in the main class, in the render() method, you should use super.render(); to use anything you want from other screen renderings!

 public void render() { clearWhite(); super.render(); } 

PS: Make sure that the class you make as a screen is, in fact, implements Screen .

Answer 2

You have an example for this and many other concepts at LibGDX.info