title: Collision not being registered in contact listener? [Libgdx + Box2d]
body: <p>Problem with collision in my game: with some entities, it's not consistent with being registered in the contact listener. Specifically, my bullets and missiles often pass right through other entities/mobs, operative word being often, as sometimes they do, and I can't really ascertain the cause for this inconsistency. I've set both of them to "bullet" for continuous collision, and they don't travel obnoxiously fast, so I'm out of ideas.</p>
  
  <p>Here is a video demonstrating the issue:</p>
  
  <p><a href="http://www.youtube.com/watch?v=FMLkg5r3dpo" rel="nofollow">http://www.youtube.com/watch?v=FMLkg5r3dpo</a></p>
  
  <p>Here is my contact listener:</p>
  
  <pre><code>public class Collisions implements ContactListener {
  
  public Collisions() {       
  }
  
  @Override
  public void beginContact(Contact contact) {
      Body a = contact.getFixtureA().getBody();
      Body b = contact.getFixtureB().getBody();
  
      if (a.getUserData() instanceof Bullet &amp;&amp; b.getUserData() instanceof Enemy) {
          Bullet bullet = (Bullet) a.getUserData();
          Enemy enemy = (Enemy) b.getUserData();
  
          enemy.harm(10);
          bullet.kill();
      } 
  
      if (a.getUserData() instanceof Missile &amp;&amp; b.getUserData() instanceof Enemy) {
          Missile missile = (Missile) a.getUserData();
          Enemy enemy = (Enemy) b.getUserData();
  
          enemy.harm(40);
          missile.kill();
      } 
  
      if (a.getUserData() instanceof Craft &amp;&amp; b.getUserData() instanceof Enemy) {
          Craft craft = (Craft) a.getUserData();
          Enemy enemy = (Enemy) b.getUserData();
  
          craft.harm(5);
          enemy.harm(10);
      } 
  }
  
  @Override
  public void endContact(Contact contact) {       
  }
  
  @Override
  public void preSolve(Contact contact, Manifold oldManifold) {       
  }
  
  @Override
  public void postSolve(Contact contact, ContactImpulse impulse) {
  }
  </code></pre>
  
  <p>}</p>