How to hide the prefab when the augmented image is not shown in ARcore?

Hi,I was testing Augmented Image example scene .The problem I faced was I cannot hide the Prefab once it comes.When I show mu camera to Augmented Image which I set ,the prefab instantiates. Once it comes, It wont go even after I remove the image.How to stop that.I only want the prefab to come when the corresponding image is present.

Code (CSharp):

1. namespace GoogleARCore.Examples.AugmentedImage
2. {
3.     using System.Collections.Generic;
4.     using System.Runtime.InteropServices;
5.     using GoogleARCore;
6.     using UnityEngine;
7.     using UnityEngine.UI;
8.  
9.     /// <summary>
10.     /// Controller for AugmentedImage example.
11.     /// </summary>
12.     public class AugmentedImageExampleController : MonoBehaviour
13.     {
14.         /// <summary>
15.         /// A prefab for visualizing an AugmentedImage.
16.         /// </summary>
17.         //  public AugmentedImageVisualizer  AugmentedImageVisualizerPrefab;
18.         public List<AugmentVisualize> prefabs = new List<AugmentVisualize>();
19.  
20.         /// <summary>
21.         /// The overlay containing the fit to scan user guide.
22.         /// </summary>
23.         public GameObject FitToScanOverlay;
24.  
25.         private Dictionary<int, AugmentVisualize> m_Visualizers
26.             = new Dictionary<int, AugmentVisualize>();
27.  
28.         private List<AugmentedImage> m_TempAugmentedImages = new List<AugmentedImage>();
29.  
30.         /// <summary>
31.         /// The Unity Update method.
32.         /// </summary>
33.         public void Update()
34.         {
35.             // Exit the app when the 'back' button is pressed.
36.             if (Input.GetKey(KeyCode.Escape))
37.             {
38.                 Application.Quit();
39.             }
40.  
41.             // Check that motion tracking is tracking.
42.             if (Session.Status != SessionStatus.Tracking)
43.             {
44.                 return;
45.             }
46.  
47.             // Get updated augmented images for this frame.
48.             Session.GetTrackables<AugmentedImage>(m_TempAugmentedImages, TrackableQueryFilter.Updated);
49.  
50.             // Create visualizers and anchors for updated augmented images that are tracking and do not previously
51.             // have a visualizer. Remove visualizers for stopped images.
52.             foreach (var image in m_TempAugmentedImages)
53.             {
54.                 AugmentVisualize visualizer = null;
55.                 m_Visualizers.TryGetValue(image.DatabaseIndex, out visualizer);
56.                 if (image.TrackingState == TrackingState.Tracking && visualizer == null)
57.                 {
58.                     // Create an anchor to ensure that ARCore keeps tracking this augmented image.
59.                     Anchor anchor = image.CreateAnchor(image.CenterPose);
60.                     visualizer = (AugmentVisualize)Instantiate(prefabs[image.DatabaseIndex], anchor.transform);
61.                     visualizer.Image = image;
62.                     m_Visualizers.Add(image.DatabaseIndex, visualizer);
63.                 }
64.                 else if (image.TrackingState == TrackingState.Stopped && visualizer != null)
65.                 {
66.                     m_Visualizers.Remove(image.DatabaseIndex);
67.                     GameObject.Destroy(visualizer.gameObject);
68.                 }
69.             }
70.  
71.             // Show the fit-to-scan overlay if there are no images that are Tracking.
72.             foreach (var visualizer in m_Visualizers.Values)
73.             {
74.                 if (visualizer.Image.TrackingState == TrackingState.Tracking)
75.                 {
76.                     FitToScanOverlay.SetActive(false);
77.                     return;
78.                 }
79.             }
80.  
81.             FitToScanOverlay.SetActive(true);
82.         }
83.     }
84. }

Code (CSharp):

1. public class AugmentVisualize : MonoBehaviour {
2.  
3.  
4.     public AugmentedImage Image;
5.  
6.     public GameObject [] Listprefabs;
7.  
8.     public Text Showtext;
9.  
10.     // Use this for initialization
11.     void Start ()
12.     {
13.      
14.     }
15.  
16.     // Update is called once per frame
17.     void Update ()
18.     {
19.  
20.         if (Image == null || Image.TrackingState == TrackingState.Paused)
21.         {
22.             //Listprefabs[Image.DatabaseIndex].SetActive(false);
23.             Listprefabs[0].SetActive(false);
24.             Listprefabs[1].SetActive(false);
25.             Showtext.text = "Paused";
26.  
27.             return;
28.         }
29.  
30.         else if(Image == null || Image.TrackingState == TrackingState.Stopped)
31.             {
32.             //Listprefabs[Image.DatabaseIndex].SetActive(false);
33.             Listprefabs[0].SetActive(false);
34.             Listprefabs[1].SetActive(false);
35.             Showtext.text = "Stopped";
36.             return;
37.         }
38.  
39.  
40.         else if (Image == null || Image.TrackingState != TrackingState.Tracking)
41.         {
42.             //Listprefabs[Image.DatabaseIndex].SetActive(false);
43.             Listprefabs[0].SetActive(false);
44.             Listprefabs[1].SetActive(false);
45.             Showtext.text = "not tracking";
46.             return;
47.         }
48.  
49.         else if(Image == null || Image.TrackingState == TrackingState.Tracking)
50.         {
51.             Listprefabs[Image.DatabaseIndex].SetActive(true);
52.             Showtext.text = "Prefab showing";
53.         }
54.  
55.     }
56. }

 

Hello.
I have the same problem. Image tracking state never gets a value of TrackingState.Stopped.
Even running example in "AugmentedImage.scene" from "Examples" in package, image (ex. 0000/earth photo) gets the frame corners placed correctly in space and I can move the phone to look around. But when I remove image from camera view frame corners still stays on the screen.
I'm using: Unity 2018.3 and arcore-unity-sdk-v1.6.0 and running an app in Galaxy S8 with Android 8.0 and latest ARCore from Play Store.

I found this info and suggested "workaround" here.