see latest posts in the thread you refer to:

https://developer.vuforia.com/forum/vuforia-40-beta/camera-not-opened-and-screen-black-vuforia-40-beta

Hi, 

Subject: Camera is black with Vuforia 4.0 beta with IOS Native UI (https://developer.vuforia.com/forum/vuforia-40-beta/camera-not-opened-and-screen-black-vuforia-40-beta)

If i run the vuforia 4.0 beta SDK with Unity3d 4.6.2, working excellent.

But when i integrate the same project with IOS native UI  (http://www.the-nerd.be/2014/08/06/add-unity3d-in-a-native-ios-application/), Camera is black.But the augmentation is working (have a look on attached image).

How to solve the issue ? Can anyone help on this? 

How to resolve this Black screnn issue ?

Thank you,

Yes @huythach , Your logic DisableARCamera and EnableARCamera logic solved my issue (tested 100 more times) !!!

Thank you. 

we found a trick for this problem by disable and enable AR camera if user opens an AR application after press home button less than 5 seconds.

It sounds like the same problem discussed here:

https://developer.vuforia.com//forum/issues-and-bugs/background-texture-access-ios-8-black-screen

This is a known issue currently under investigation.

Hi,

Am also facing the same Black screen issue.

i have created a post https://developer.vuforia.com/forum/device-support/black-screen-ios-devices-camera-mode#comment-2045304.

meanwhile, Let me check with your logic !!! i hope it would work !!!

After working around, we found a trick for this problem by disable and enable AR camera if user opens an AR application after press home button less than 5 seconds.

This may be not the best solution, but it solves our problem now.

Looking forward to information from Vuforia SDK development team.

using UnityEngine;
using System;
using System.Collections;

public class GoToBackgroundController : MonoBehaviour
{
	
	private const int MAX_WAITING_TIME = 5;
	private int pauseStartTime = 0;
	
	void OnApplicationPause (bool pauseStatus)
	{
		// Pause
        if (pauseStatus == true)
        {
			// Update variable
            pauseStartTime = GetUnixTime(DateTime.Now);
        }
        // Resume
        else
        {
            int resumeTime = GetUnixTime(DateTime.Now);

            // Wake up in less than 5 seconds, we need to restart AR camera
            if (resumeTime < pauseStartTime + MAX_WAITING_TIME)
            {
                StartCoroutine(RestartARCamera());
            }
        }
	}
	
	private IEnumerator RestartARCamera ()
	{
		yield return new WaitForEndOfFrame();
		
		// Disable AR camera
		DisableARCamera();
		
		// Wait for 1 second before enable AR camera
		yield return new WaitForSeconds(1.0f);
		
		// Enable AR camera
		EnableARCamera();
	}
	
	private static DateTime Unix_Epoch = new DateTime(1970, 1, 1, 0, 0, 0, 0);

    private int GetUnixTime (DateTime targetTime)
    {
		targetTime = targetTime.ToUniversalTime();
        TimeSpan elspeedTime = targetTime - Unix_Epoch;

        return (int)elspeedTime.TotalSeconds;
    }
	
	private void DisableARCamera ()
	{
		CameraDevice.Instance.Deinit();
		CameraDevice.Instance.Stop();
	}
	
	private void EnableARCamera ()
	{
		CameraDevice.Instance.Init(CameraDevice.CameraDirection.CAMERA_BACK);
		CameraDevice.Instance.Start();
        CameraDevice.Instance.SetFocusMode(CameraDevice.FocusMode.FOCUS_MODE_CONTINUOUSAUTO);
	}
}