comment utiliser le libgdx contactlistener

Voici un court exemple pour libgdx. Il montre comment créer un ContactListener pour afficher les luminaires sont impliqués lorsque des contacts sont pris et brisé. Il montre également l'utilisation de monde.getContactList() qui sera de retour une liste de contacts qui existent encore après l'étape de la physique. Cela peut manquer des contacts qui ont été fait et rompu au cours de l'étape de la physique. Si vous êtes intéressé par ces choses, alors vous aurez envie de mettre en œuvre un ContactListener, à l'aide de beginContact() pour détecter quand les contacts sont pris et endContact() à détecter si elles sont cassées.

package hacks;
import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.backends.lwjgl.LwjglApplication;
import com.badlogic.gdx.backends.lwjgl.LwjglApplicationConfiguration;
import com.badlogic.gdx.graphics.GL10;
import com.badlogic.gdx.graphics.OrthographicCamera;
import com.badlogic.gdx.math.MathUtils;
import com.badlogic.gdx.math.Vector2;
import com.badlogic.gdx.physics.box2d.Body;
import com.badlogic.gdx.physics.box2d.BodyDef;
import com.badlogic.gdx.physics.box2d.BodyDef.BodyType;
import com.badlogic.gdx.physics.box2d.Box2DDebugRenderer;
import com.badlogic.gdx.physics.box2d.Contact;
import com.badlogic.gdx.physics.box2d.ContactImpulse;
import com.badlogic.gdx.physics.box2d.ContactListener;
import com.badlogic.gdx.physics.box2d.Fixture;
import com.badlogic.gdx.physics.box2d.FixtureDef;
import com.badlogic.gdx.physics.box2d.Manifold;
import com.badlogic.gdx.physics.box2d.PolygonShape;
import com.badlogic.gdx.physics.box2d.World;
public class Box2DDemoMain extends com.badlogic.gdx.Game {
private static final float SCALING = 0.1f;
private Box2DDebugRenderer debugRenderer;
private OrthographicCamera camera;
private World world;
@Override
public void create() {
debugRenderer = new Box2DDebugRenderer();
camera = new OrthographicCamera();
createWorld();
createCollisionListener();
createGround();
createBox();
}
private void createWorld() {
Vector2 gravity = new Vector2(0, -10);
world = new World(gravity, true);
}
private void createCollisionListener() {
world.setContactListener(new ContactListener() {
@Override
public void beginContact(Contact contact) {
Fixture fixtureA = contact.getFixtureA();
Fixture fixtureB = contact.getFixtureB();
Gdx.app.log("beginContact", "between " + fixtureA.toString() + " and " + fixtureB.toString());
}
@Override
public void endContact(Contact contact) {
Fixture fixtureA = contact.getFixtureA();
Fixture fixtureB = contact.getFixtureB();
Gdx.app.log("endContact", "between " + fixtureA.toString() + " and " + fixtureB.toString());
}
@Override
public void preSolve(Contact contact, Manifold oldManifold) {
}
@Override
public void postSolve(Contact contact, ContactImpulse impulse) {
}
});
}
private void createGround() {
PolygonShape groundShape = new PolygonShape();
groundShape.setAsBox(50, 1);
BodyDef groundBodyDef = new BodyDef();
groundBodyDef.type = BodyType.StaticBody;
groundBodyDef.position.set(0, -20);
Body groundBody = world.createBody(groundBodyDef);
FixtureDef fixtureDef = new FixtureDef();
fixtureDef.shape = groundShape;
groundBody.createFixture(fixtureDef);
groundShape.dispose();
}
private void createBox() {
PolygonShape boxShape = new PolygonShape();
boxShape.setAsBox(1, 1);
BodyDef boxBodyDef = new BodyDef();
boxBodyDef.position.set(0, 20);
boxBodyDef.angle = MathUtils.PI / 32;
boxBodyDef.type = BodyType.DynamicBody;
boxBodyDef.fixedRotation = false;
Body boxBody = world.createBody(boxBodyDef);
FixtureDef boxFixtureDef = new FixtureDef();
boxFixtureDef.shape = boxShape;
boxFixtureDef.restitution = 0.75f;
boxFixtureDef.density = 2.0f;
boxBody.createFixture(boxFixtureDef);
boxShape.dispose();
}
@Override
public void resize(int width, int height) {
super.resize(width, height);
float cameraWidth = Gdx.graphics.getWidth() * SCALING;
float cameraHeight = Gdx.graphics.getHeight() * SCALING;
camera.setToOrtho(false, cameraWidth, cameraHeight);
camera.position.set(0, 0, 0);
}
@Override
public void render() {
super.render();
world.step(Gdx.graphics.getDeltaTime(), 8, 3);
int numContacts = world.getContactCount();
if (numContacts > 0) {
Gdx.app.log("contact", "start of contact list");
for (Contact contact : world.getContactList()) {
Fixture fixtureA = contact.getFixtureA();
Fixture fixtureB = contact.getFixtureB();
Gdx.app.log("contact", "between " + fixtureA.toString() + " and " + fixtureB.toString());
}
Gdx.app.log("contact", "end of contact list");
}
Gdx.gl.glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT);
camera.update();
debugRenderer.render(world, camera.combined);
}
public static void main(String[] args) {
LwjglApplicationConfiguration config = new LwjglApplicationConfiguration();
config.title = Box2DDemoMain.class.getName();
config.width = 800;
config.height = 480;
config.fullscreen = false;
config.useGL20 = true;
config.useCPUSynch = true;
config.forceExit = true;
config.vSyncEnabled = true;
new LwjglApplication(new Box2DDemoMain(), config);
}
}

OriginalL'auteur Rod Hyde