# Interface ARTrackingListener

public interface ARTrackingListener
Observes changes to a session's overall tracking quality. Register through `ARSession#addTrackingListener(ARTrackingListener)`; events are delivered on the EDT.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `void`
  `trackingStateChanged(ARSession session, ARTrackingState state, ARTrackingFailureReason reason)`
  Invoked on the EDT when the session's tracking state changes.

- ## Method Details

  - ### trackingStateChanged

    void trackingStateChanged(ARSession session, ARTrackingState state, ARTrackingFailureReason reason)

    Invoked on the EDT when the session's tracking state changes.

    ###### Parameters

    - `session`: the session whose state changed

    - `state`: the new tracking state

    - `reason`: why tracking is degraded, or `ARTrackingFailureReason#NONE` when it is not