title: QR detection using ZXing with Vuforia in Unity
body: <p>We have implemented the QR detection functionality using ZXing.dll in Unity 5.3.4f1 with Vuforia Unity SDK 5.5.9. We have a QR detection script on GameObject which remains active throughout the app and using below mentioned (QRScanner.cs) code ( as mentioned on <a href="https://stackoverflow.com/questions/30546548/unity-zxing-qr-code-scanner-integration">Unity Zxing QR code scanner integration</a> ).</p>
  
  <p>We are also using Vuforia for image detection (50 image targets) in the same scene where QR detection is expected. The Vuforia plugin is getting enabled / disabled multiple times as per our requirement. Both the image and QR detection is working perfectly for us on Android and iOS devices until the app is in focus. Whenever VuforiaBehaviour gets disabled and enabled, QR detection stops working after that. QRScanner script always receives null data after the app is resumed or AR camera is reloaded. We have tried keeping our QR detection script on AR camera prefab and also tried</p>
  
  <blockquote>
    <p>qcarBehaviour.RegisterTrackablesUpdatedCallback(OnTrackablesUpdated);
    qcarBehaviour.RegisterQCARStartedCallback(OnTrackablesUpdated);</p>
  </blockquote>
  
  <p>callbacks every time AR camera starts but with no success. The QR detection stops working completely after pausing Vuforia plugin for any reason.</p>
  
  <p>Does anybody have any idea how to fix this issue?</p>
  
  <pre><code>QRScanner.cs
  
    using UnityEngine;
    using System;
    using System.Collections;
    using Vuforia;
    using System.Threading;
    using ZXing;
    using ZXing.QrCode;
    using ZXing.Common;
  
    /*        /////////////////   QR detection does not work in editor    ////////////////    */
  
    [AddComponentMenu("System/QRScanner")]
    public class QRScanner : MonoBehaviour
    { 
      private bool cameraInitialized;
      private BarcodeReader barCodeReader;
      public AppManager camScript;
  
      void Start()
      { 
          barCodeReader = new BarcodeReader();
          StartCoroutine(InitializeCamera());
      }
  
      private IEnumerator InitializeCamera()
      {
          // Waiting a little seem to avoid the Vuforia's crashes.
          yield return new WaitForSeconds(3f);
  
          var isFrameFormatSet = CameraDevice.Instance.SetFrameFormat(Image.PIXEL_FORMAT.RGB888, true);
          Debug.Log(String.Format("FormatSet : {0}", isFrameFormatSet));
  
          // Force autofocus.
    //        var isAutoFocus = CameraDevice.Instance.SetFocusMode(CameraDevice.FocusMode.FOCUS_MODE_CONTINUOUSAUTO);
    //        if (!isAutoFocus)
    //        {
    //            CameraDevice.Instance.SetFocusMode(CameraDevice.FocusMode.FOCUS_MODE_NORMAL);
    //        }
    //        Debug.Log(String.Format("AutoFocus : {0}", isAutoFocus));
          cameraInitialized = true;
      }
  
      private void Update()
      {
          if (cameraInitialized)
          {
              try
              {
                  var cameraFeed = CameraDevice.Instance.GetCameraImage(Image.PIXEL_FORMAT.RGB888);
                  if (cameraFeed == null)
                  {
                      return;
                  }
                  var data = barCodeReader.Decode(cameraFeed.Pixels, cameraFeed.BufferWidth, cameraFeed.BufferHeight, RGBLuminanceSource.BitmapFormat.RGB24);
                  if (data != null)
                  {
                      // QRCode detected.
                      Debug.Log(data.Text);
                      Application.OpenURL (data.Text); // our function to call and pass url as text
                      data = null;        // clear data
                  }
                  else
                  {
                      Debug.Log("No QR code detected !");
                  }
              }
              catch (Exception e)
              {
                  Debug.LogError(e.Message);
              }
          }
      }
    }
  </code></pre>