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Libgdx Box2D - Collision detection

 3 years ago
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Libgdx Box2D - Collision detection

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I am trying detect player collisions with a sensor body. Imagine a collectible in a platformer... I want to run an event when the player collides with the collectible.

As you will see from my code, I am attaching a dynamic body to the collectible object as well as a sensor body which I am hoping to attach a player collision 'event' to when the player collides with the sensor. It seems there is a "ContactListener" interface, but implementing the methods don't seem to do anything. How would I go about doing this?

If there is a better way of doing any of the below, any advice would be appreciated :)

import com.badlogic.gdx.math.Vector2;
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.FixtureDef;
import com.badlogic.gdx.physics.box2d.Manifold;
import com.badlogic.gdx.physics.box2d.PolygonShape;
import com.badlogic.gdx.physics.box2d.BodyDef.BodyType;

public class CoinCollectible extends GameObject{

    public CoinCollectible(Vector2 position, float angle){
        bodyDef.type = BodyType.DynamicBody;
        bodyDef.position.x = position.x;
        bodyDef.position.y = position.y;
        bodyDef.angle = angle;

        PolygonShape poly = new PolygonShape();
        poly.setAsBox(1, 1);
        FixtureDef itemFixture = new FixtureDef();
        itemFixture.shape = poly;
        itemFixture.density = 1;
        itemFixture.filter.categoryBits = PhysicsLayers.LAYER_ITEM;
        itemFixture.filter.maskBits = PhysicsLayers.MASK_PLAYER;
        fixtureArray.add(itemFixture);

        massData.mass = 1f;

        // Attach a collision sensor
        FixtureDef sensorFixture = new FixtureDef();
        sensorFixture.shape = poly;
        sensorFixture.isSensor = true;
        sensorFixture.filter.maskBits = PhysicsLayers.LAYER_PLAYER;

        fixtureArray.add(sensorFixture);

        // Clean up
        poly.dispose();

    }
}

import java.util.ArrayList;
import java.util.List;

import com.badlogic.gdx.physics.box2d.Body;
import com.badlogic.gdx.physics.box2d.BodyDef;
import com.badlogic.gdx.physics.box2d.FixtureDef;
import com.badlogic.gdx.physics.box2d.MassData;
import com.badlogic.gdx.physics.box2d.World;

public class GameObject{

    public Body body = null;
    public BodyDef bodyDef = new BodyDef();
    public MassData massData = new MassData();

    protected List<FixtureDef> fixtureArray = new ArrayList<FixtureDef>();

    public GameObject(){}

    public Body addToWorld(World world){
        if(bodyDef == null)
            return null;

        body = world.createBody(bodyDef);

        while(fixtureArray.size() > 0){
            body.createFixture(fixtureArray.remove(0));
        }

        body.setMassData(massData);

        return body;
    }

}

Try add this line in your code (at coin constructor):

bodyDef.userData = this;

And your contact listener, get userdata and casting into GameObject, then, for example, call event collision.

Greetings


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