title: Unity android application doesn't quit
body: <p>I create an android application by generate <code>.apk</code> using unity3d-vuforia. When I click <code>back</code> button, the app doesn't quit. I handle press back button. </p>
  
  <p>I edit <code>customEventHandler.cs</code> file that is created by unity.
  My code is here : </p>
  
  <pre><code>using UnityEngine;
  using System.Collections;
  
  public class customEventHandler : MonoBehaviour {
  
  // Use this for initialization
  void Start () {
  }
  
  // Update is called once per frame
  void Update () {
      if(Input.GetKeyDown(KeyCode.Escape))
      {
          Application.Quit();
          // or ask to quit
      }
  }
  }
  </code></pre>
  
  <p>I don't sure whethet I can add it. I have a 2d marker and a virtual car. The car is 3d object. I check event handler, my screenshot is below :</p>
  
  <p><img src="https://i.stack.imgur.com/OoxTZ.png" alt="enter image description here"></p>
  
  <p><strong>EDIT</strong></p>
  
  <p>I solve the problem using below code. I don't delete this post because matbe the solution hepls someone. I edited <code>ImageTargetBehaviour.cs</code> file.</p>
  
  <pre><code>using System.Collections.Generic;
  using UnityEngine;
  
   /// &lt;summary&gt;
   /// This class serves both as an augmentation definition for an ImageTarget  in the editor
  /// as well as a tracked image target result at runtime
  /// &lt;/summary&gt;
   public class ImageTargetBehaviour : ImageTargetAbstractBehaviour
   {
   void OnGUI () {
  
      // call this block
      if(Input.GetKeyDown(KeyCode.Escape))
      {
          Application.Quit();
          // or ask to quit
      }
     }
     }
  </code></pre>