Refactor entity.PhysicsBody to physics.PhysicsBody

Create CollisionListener interface and Box2dContactListener
Register the Box2dContactListener with the box2d world

core/src/com/me/brickbuster/entity/Ball.java

@@ -10,6 +10,7 @@ import com.badlogic.gdx.physics.box2d.Body;
 import com.badlogic.gdx.physics.box2d.BodyDef;
 import com.badlogic.gdx.physics.box2d.CircleShape;
 import com.badlogic.gdx.physics.box2d.FixtureDef;
+import com.me.brickbuster.physics.PhysicsBody;
 import com.me.brickbuster.state.PlayState;
 
 public class Ball extends Entity implements PhysicsBody {

core/src/com/me/brickbuster/entity/Brick.java

@@ -9,6 +9,7 @@ import com.badlogic.gdx.physics.box2d.BodyDef;
 import com.badlogic.gdx.physics.box2d.FixtureDef;
 import com.badlogic.gdx.physics.box2d.PolygonShape;
 import com.me.brickbuster.entity.powerup.PowerUpType;
+import com.me.brickbuster.physics.PhysicsBody;
 import com.me.brickbuster.state.PlayState;
 
 public class Brick extends Entity implements PhysicsBody {

core/src/com/me/brickbuster/entity/Paddle.java

@@ -10,6 +10,7 @@ import com.badlogic.gdx.physics.box2d.Body;
 import com.badlogic.gdx.physics.box2d.BodyDef;
 import com.badlogic.gdx.physics.box2d.EdgeShape;
 import com.badlogic.gdx.physics.box2d.FixtureDef;
+import com.me.brickbuster.physics.PhysicsBody;
 import com.me.brickbuster.state.PlayState;
 import net.dermetfan.utils.Pair;
 

core/src/com/me/brickbuster/entity/powerup/PowerUp.java

@@ -10,7 +10,7 @@ import com.badlogic.gdx.physics.box2d.CircleShape;
 import com.badlogic.gdx.physics.box2d.FixtureDef;
 import com.me.brickbuster.Utils;
 import com.me.brickbuster.entity.Entity;
-import com.me.brickbuster.entity.PhysicsBody;
+import com.me.brickbuster.physics.PhysicsBody;
 import com.me.brickbuster.state.PlayState;
 import net.dermetfan.utils.Pair;
 

core/src/com/me/brickbuster/physics/Box2dContactListener.java

@@ -0,0 +1,53 @@
+package com.me.brickbuster.physics;
+
+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.Manifold;
+import com.me.brickbuster.entity.Entity;
+
+public class Box2dContactListener implements ContactListener {
+
+	@Override
+	public void beginContact(Contact contact) {
+		Object userDataA = contact.getFixtureA().getBody().getUserData();
+		Object userDataB = contact.getFixtureB().getBody().getUserData();
+
+		if (userDataA == null || userDataB == null ||
+				!(userDataA instanceof Entity) || !(userDataB instanceof Entity)) {
+			return;
+		}
+
+		if (userDataA instanceof CollisionListener) {
+			((CollisionListener) userDataA).beginContact((Entity) userDataB);
+		}
+		if (userDataB instanceof CollisionListener) {
+			((CollisionListener) userDataB).beginContact((Entity) userDataA);
+		}
+	}
+
+	@Override
+	public void endContact(Contact contact) {
+		Object userDataA = contact.getFixtureA().getBody().getUserData();
+		Object userDataB = contact.getFixtureB().getBody().getUserData();
+
+		if (userDataA == null || userDataB == null ||
+				!(userDataA instanceof Entity) || !(userDataB instanceof Entity)) {
+			return;
+		}
+
+		if (userDataA instanceof CollisionListener) {
+			((CollisionListener) userDataA).endContact((Entity) userDataB);
+		}
+		if (userDataB instanceof CollisionListener) {
+			((CollisionListener) userDataB).endContact((Entity) userDataA);
+		}
+	}
+
+	@Override
+	public void preSolve(Contact contact, Manifold oldManifold) {}
+
+	@Override
+	public void postSolve(Contact contact, ContactImpulse impulse) {}
+
+}

core/src/com/me/brickbuster/physics/CollisionListener.java

@@ -0,0 +1,11 @@
+package com.me.brickbuster.physics;
+
+import com.me.brickbuster.entity.Entity;
+
+public interface CollisionListener {
+
+	void beginContact(Entity contacted);
+
+	void endContact(Entity contacted);
+
+}

core/src/com/me/brickbuster/physics/PhysicsBody.java

@@ -1,4 +1,4 @@
-package com.me.brickbuster.entity;
+package com.me.brickbuster.physics;
 
 import com.badlogic.gdx.physics.box2d.Body;
 
@@ -6,6 +6,4 @@ public interface PhysicsBody {
 
 	Body getBody();
 
-	//public void handleCollission(Entity other);
-
 }

core/src/com/me/brickbuster/state/PlayState.java

@@ -11,6 +11,7 @@ import com.me.brickbuster.entity.Ball;
 import com.me.brickbuster.entity.Brick;
 import com.me.brickbuster.entity.Paddle;
 import com.me.brickbuster.entity.powerup.*;
+import com.me.brickbuster.physics.Box2dContactListener;
 
 import java.util.*;
 
@@ -59,6 +60,7 @@ public class PlayState extends State {
 	public void setup() {
 		// Initialize a world with no gravity
 		world = new World(new Vector2(), false);
+		world.setContactListener(new Box2dContactListener());
 
 		// define a playArea body with position set to 0
 		BodyDef playAreaDef = new BodyDef();