JavaFX: Space Invaders in less than 175 LOC

Toni EppleFebruary 19th, 2013Last Updated: February 19th, 2013

2 269 3 minutes read

With the current version of the API I’m at less than 175 LOC for Space Invaders. I’ve got lot’s of “Functional Interfaces” in my APIs that can be converted to Lambda Expressions with JavaFX 8( e.g. SpriteProvider and CollisionHandler). That will make the code nicer and shorter. I could probably also reduce the linecount by bundling the recources (e.g. TileSets) and creating more factories and Builders (SpriteBuilder). But I’m getting closer to what I want…

package de.eppleton.fx2d.samples.spaceinvaders;

import de.eppleton.fx2d.collision.*;
import de.eppleton.fx2d.*;
import de.eppleton.fx2d.action.*;
import de.eppleton.fx2d.tileengine.*;
import java.util.Collection;
import java.util.logging.*;
import javafx.beans.property.DoubleProperty;
import javafx.beans.property.SimpleDoubleProperty;
import javafx.scene.canvas.*;
import javafx.scene.input.*;
import javafx.scene.media.*;
import javafx.scene.paint.Color;
import javafx.scene.text.Font;
import javax.xml.bind.JAXBException;
import org.openide.util.Lookup;
import org.openide.util.lookup.Lookups;

public class SpaceInvaders extends Game {

    Points TEN = new Points(10);
    Points TWENTY = new Points(30);
    Points THIRTY = new Points(40);
    DoubleProperty invaderXVelocity = new SimpleDoubleProperty(0.3);
    AudioClip shootSound = new AudioClip(SpaceInvaders.class.getResource('/assets/sound/shoot.wav').toString());
    AudioClip invaderKilledSound = new AudioClip(SpaceInvaders.class.getResource('/assets/sound/invaderkilled.wav').toString());
    MediaPlayer mediaPlayer = new MediaPlayer(new Media(SpaceInvaders.class.getResource('/assets/sound/invader_loop1.mp3').toString()));
    int score = 0;
    String message;
    int[][] enemies = new int[][]{
        {30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30},
        {20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20},
        {20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20},
        {10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10},
        {10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10}
    };

    @Override
    protected void initGame() {
        final GameCanvas canvas = getCanvas();
        try {
            TileSet invaders = TileMapReader.readSet('/assets/graphics/invaders1.tsx');
            TileSet playerTiles = TileMapReader.readSet('/assets/graphics/player.tsx');
            final TileSetAnimation animation30 = new TileSetAnimation(invaders, new int[]{0, 1}, 2);
            final TileSetAnimation animation10 = new TileSetAnimation(invaders, new int[]{4, 5}, 2);
            final TileSetAnimation animation20 = new TileSetAnimation(invaders, new int[]{2, 3}, 2);
            final TileSetAnimation playerAnimation = new TileSetAnimation(playerTiles, new int[]{0}, 100_000);
            for (int i = 0; i < enemies.length; i++) {
                int[] is = enemies[i];
                for (int j = 0; j < is.length; j++) {
                    Points points = is[j] == 30 ? THIRTY : is[j] == 20 ? TWENTY : TEN;
                    Sprite sprite = new Sprite(canvas, '' + ((j * 11) + i), 50 + (40 * j), 140 + (40 * i), 30, 20, Lookups.fixed(points));
                    sprite.setAnimation(is[j] == 30 ? animation30 : is[j] == 20 ? animation20 : animation10);
                    sprite.setVelocityXProperty(invaderXVelocity);
                }
            }
            Sprite player = new Sprite(canvas, playerAnimation, 'Player', 350, 620, 40, 30, Lookup.EMPTY);
            player.setAnimation(playerAnimation);
            player.addAction(KeyCode.LEFT, ActionFactory.createMoveAction(playerAnimation, 'left', -4, 0, 0, 0));
            player.addAction(KeyCode.RIGHT, ActionFactory.createMoveAction(playerAnimation, 'right', 4, 0, 0, 0));
            player.addAction(KeyCode.UP, new ShootAction(playerAnimation, 'fire', new BulletProvider(), new HitHandler(), shootSound));
        } catch (JAXBException ex) {
            Logger.getLogger(SpaceInvaders.class.getName()).log(Level.SEVERE, null, ex);
        }
        canvas.addLayer(new Background());
        canvas.addBehaviour(new MoveInvadersBehavior());
        mediaPlayer.setCycleCount(MediaPlayer.INDEFINITE);
        mediaPlayer.play();
        canvas.addLayer(new SpriteLayer());
        canvas.start();
    }

    @Override
    protected double getViewPortWidth() {
        return 700;
    }

    @Override
    protected double getViewPortHeight() {
        return 700;
    }

    public static void main(String[] args) {
        launch(args);
    }

    private class Points {

        int points;

        public Points(int points) {
            this.points = points;
        }

        public int getPoints() {
            return points;
        }
    }

    static class BulletProvider implements SpriteProvider {

        @Override
        public Sprite getSprite(GameCanvas parent, double x, double y) {
            return new Sprite(parent, 'bullet', x, y + 10, 10, 20, Lookup.EMPTY);
        }
    }

    class HitHandler implements CollisionHandler {

        @Override
        public void handleCollision(Collision collision) {
            Points points = collision.getSpriteTwo().getLookup().lookup(Points.class);
            if (points != null) {
                score += points.getPoints();
                invaderKilledSound.play();
                collision.getSpriteOne().remove();
                collision.getSpriteTwo().remove();
            }
        }
    }

    class MoveInvadersBehavior extends Behavior {

        @Override
        public boolean perform(GameCanvas canvas, long nanos) {
            Collection<Sprite> sprites = canvas.getSprites();
            boolean stop = false;
            boolean win = true;
            for (Sprite sprite1 : sprites) {
                if (sprite1.getLookup().lookup(Points.class) != null) {
                    win = false;
                    if (sprite1.getX() > 650 || sprite1.getX() < 50) {
                        invaderXVelocity.set(-invaderXVelocity.doubleValue() * (stop ? 0 : 1.3));
                        if (sprite1.getY() >= 600) {
                            message = 'Game Over!';
                            stop = true;
                            mediaPlayer.stop();
                        }
                        for (Sprite sprite2 : sprites) {
                            if (sprite2.getLookup().lookup(Points.class) != null) {
                                sprite2.setY(sprite2.getY() + (stop ? 0 : 20));
                            }
                        }
                        break;
                    }
                }
            }
            if (win) {
                message = 'You win!';
                canvas.stop();
                mediaPlayer.stop();
            }
            return true;
        }
    }

    class Background extends Layer {        

        @Override
        public void draw(GraphicsContext graphicsContext, double x, double y, double width, double height) {
            graphicsContext.setFill(Color.BLACK);
            graphicsContext.fillRect(0, 0, width, height);
            graphicsContext.setFill(Color.WHITE);
            graphicsContext.setFont(Font.font('OCR A Std', 20));
            graphicsContext.fillText('SCORE<1>    HI-SCORE    SCORE<2>', 30, 30);
            graphicsContext.fillText('' + score + '            9990   ', 30, 60);
            graphicsContext.fillText(message, 300, 400);
            graphicsContext.fillText('' + 3 + '                   CREDIT ' + 1, 30, 680);
            graphicsContext.setFill(Color.GREEN);
            graphicsContext.fillRect(30, 650, 640, 4);
        }
    }
}

Here’s a video of the game: