# Interface ContactListener

public interface ContactListener

Notified when bodies in a `PhysicsWorld` start and stop touching. Register with `PhysicsWorld#addContactListener(ContactListener)`.

Callbacks fire from inside `PhysicsWorld#step(float)` -- i.e. on the game loop thread -- so it is safe to read and update game state directly, but you must not create or destroy bodies during the callback (defer that until after `step` returns).

- ## Method Summary

  Modifier and Type
  Method
  Description
  `void`
  `beginContact(PhysicsContact contact)`
  Called when two fixtures begin touching.
  `void`
  `endContact(PhysicsContact contact)`
  Called when two fixtures stop touching.

- ## Method Details

  - ### beginContact

    void beginContact(PhysicsContact contact)
    Called when two fixtures begin touching.

  - ### endContact

    void endContact(PhysicsContact contact)
    Called when two fixtures stop touching.