How to write KeyListener for JavaFX

From the JavaRanch Forum Post .

Key press and release ramps are added to the stage and update the motion state variables recorded in the application. The animation timer connects to the JavaFX pulse engine (which will be closed by default to trigger the event 60 times per second), so it's kind of a game loop. The timer checks for the move state variables and applies their delta actions to the character position, which effectively moves the character around the screen in response to keystrokes.

import javafx.animation.AnimationTimer;
import javafx.application.Application;
import javafx.event.EventHandler;
import javafx.scene.*;
import javafx.scene.image.*;
import javafx.scene.input.KeyEvent;
import javafx.scene.paint.Color;
import javafx.stage.Stage;

/**
 * Hold down an arrow key to have your hero move around the screen.
 * Hold down the shift key to have the hero run.
 */
public class Runner extends Application {

    private static final double W = 600, H = 400;

    private static final String HERO_IMAGE_LOC =
            "http://icons.iconarchive.com/icons/raindropmemory/legendora/64/Hero-icon.png";

    private Image heroImage;
    private Node  hero;

    boolean running, goNorth, goSouth, goEast, goWest;

    @Override
    public void start(Stage stage) throws Exception {
        heroImage = new Image(HERO_IMAGE_LOC);
        hero = new ImageView(heroImage);

        Group dungeon = new Group(hero);

        moveHeroTo(W / 2, H / 2);

        Scene scene = new Scene(dungeon, W, H, Color.FORESTGREEN);

        scene.setOnKeyPressed(new EventHandler<KeyEvent>() {
            @Override
            public void handle(KeyEvent event) {
                switch (event.getCode()) {
                    case UP:    goNorth = true; break;
                    case DOWN:  goSouth = true; break;
                    case LEFT:  goWest  = true; break;
                    case RIGHT: goEast  = true; break;
                    case SHIFT: running = true; break;
                }
            }
        });

        scene.setOnKeyReleased(new EventHandler<KeyEvent>() {
            @Override
            public void handle(KeyEvent event) {
                switch (event.getCode()) {
                    case UP:    goNorth = false; break;
                    case DOWN:  goSouth = false; break;
                    case LEFT:  goWest  = false; break;
                    case RIGHT: goEast  = false; break;
                    case SHIFT: running = false; break;
                }
            }
        });

        stage.setScene(scene);
        stage.show();

        AnimationTimer timer = new AnimationTimer() {
            @Override
            public void handle(long now) {
                int dx = 0, dy = 0;

                if (goNorth) dy -= 1;
                if (goSouth) dy += 1;
                if (goEast)  dx += 1;
                if (goWest)  dx -= 1;
                if (running) { dx *= 3; dy *= 3; }

                moveHeroBy(dx, dy);
            }
        };
        timer.start();
    }

    private void moveHeroBy(int dx, int dy) {
        if (dx == 0 && dy == 0) return;

        final double cx = hero.getBoundsInLocal().getWidth()  / 2;
        final double cy = hero.getBoundsInLocal().getHeight() / 2;

        double x = cx + hero.getLayoutX() + dx;
        double y = cy + hero.getLayoutY() + dy;

        moveHeroTo(x, y);
    }

    private void moveHeroTo(double x, double y) {
        final double cx = hero.getBoundsInLocal().getWidth()  / 2;
        final double cy = hero.getBoundsInLocal().getHeight() / 2;

        if (x - cx >= 0 &&
            x + cx <= W &&
            y - cy >= 0 &&
            y + cy <= H) {
            hero.relocate(x - cx, y - cy);
        }
    }

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