cleanup physic bodies

core/src/main/java/io/github/com/quillraven/screen/GameScreen.java

@@ -9,6 +9,7 @@ import com.badlogic.gdx.physics.box2d.World;
 import com.badlogic.gdx.utils.Disposable;
 import io.github.com.quillraven.GdxGame;
 import io.github.com.quillraven.asset.MapAsset;
+import io.github.com.quillraven.system.CleanupSystem;
 import io.github.com.quillraven.system.PhysicDebugRenderSystem;
 import io.github.com.quillraven.system.RenderSystem;
 import io.github.com.quillraven.system.TiledServiceTestSystem;
@@ -32,6 +33,7 @@ public class GameScreen extends ScreenAdapter {
 
         // add ECS systems
         this.engine.addSystem(new RenderSystem(game.getBatch(), game.getViewport(), game.getCamera()));
+        this.engine.addSystem(new CleanupSystem());
         this.engine.addSystem(new TiledServiceTestSystem(this.tiledService));
         this.engine.addSystem(new PhysicDebugRenderSystem(this.physicWorld, game.getCamera()));
     }

core/src/main/java/io/github/com/quillraven/system/CleanupSystem.java

@@ -0,0 +1,41 @@
+package io.github.com.quillraven.system;
+
+import com.badlogic.ashley.core.Engine;
+import com.badlogic.ashley.core.Entity;
+import com.badlogic.ashley.core.EntityListener;
+import com.badlogic.ashley.core.EntitySystem;
+import com.badlogic.ashley.core.Family;
+import com.badlogic.gdx.physics.box2d.Body;
+import io.github.com.quillraven.component.Physic;
+
+public class CleanupSystem extends EntitySystem implements EntityListener {
+
+    @Override
+    public void addedToEngine(Engine engine) {
+        super.addedToEngine(engine);
+        engine.addEntityListener(Family.all(Physic.class).get(), this);
+    }
+
+    @Override
+    public void removedFromEngine(Engine engine) {
+        super.removedFromEngine(engine);
+        engine.removeEntityListener(this);
+    }
+
+    @Override
+    public void entityAdded(Entity entity) {
+    }
+
+    @Override
+    public void entityRemoved(Entity entity) {
+        // !!! Important !!!
+        // This does not work if the Physic component gets removed from an entity
+        // because the component is no longer accessible here.
+        // This ONLY works when an entity with a Physic component gets removed entirely from the engine.
+        Physic physic = Physic.MAPPER.get(entity);
+        if (physic != null) {
+            Body body = physic.body();
+            body.getWorld().destroyBody(body);
+        }
+    }
+}