Damm even I am having a similar kind of issue, I have searched all over the internet and even have posted on number of threads on different forum, no solution seems to work. I am really frustrated, can anyone of you here help me resolve this issue, I am very much tired now. mx player

Hi, 

I used Vuforia 6.9.3 and Unity 2019.4.7

I found this error occurs because my ModelTarget script used before the apps asks for camera permission at the first instalation. I resolve this by added new scene to request permission before enter AR scene.

Hi,

Could you please confirm the Vuforia Engine and Unity version?

Thank you.

Vuforia Engine Support

Hi,

Apparently the error only occurs when it is first installed in iOS device. I don't know why.

Hi,

Ok, could you add your Model Target database to the Core sample app and let me know if you can cycle through the guideviews?

Thank you.

Vuforia Engine Support

Thank you for the reply.

I tried the core sample but it has same error when i click CycleGuideView button.

The error in this line,

int activeView = modelTarget.GetActiveGuideViewIndex();

ModelTarget is NullReferenceException

Hi,

Its quite strange that it fails on iOS and works in PlayMode and Android.

In our Core Sample apps we demo how Model Targets and also cycle throught the guideview with following code:

/// <summary>

    /// Cycles through guide views for Standard Model Targets with multiple views.

    /// </summary>

    public void CycleGuideView()

    {

        VLog.Log("cyan", "CycleGuideView() called.");

        if (this.modelStandard != null)

        {

            ModelTarget modelTarget = this.modelStandard.ModelTarget;

            int activeView = modelTarget.GetActiveGuideViewIndex();

            int totalViews = modelTarget.GetNumGuideViews();

            if (totalViews > 1 && activeView > -1)

            {

                int guideViewIndexToActivate = (activeView + 1) % totalViews;

                VLog.Log("yellow",

                    modelTarget.Name + ": Activating Guide View Index " +

                    guideViewIndexToActivate.ToString() + " of " +

                    totalViews.ToString() + " total Guide Views.");

                modelTarget.SetActiveGuideViewIndex(guideViewIndexToActivate);

            }

            else

            {

                VLog.Log("yellow",

                    "GuideView was not cycled." +

                    "\nActive Guide View Index = " + activeView +

                    "\nNumber of Guide Views = " + totalViews);

            }

        }

    }

The code is available under ModelTargetManager.cs and the core sample are available through Unity Asset Store.

My advice would be to use our implementation as it works on iOS and Android.

Thank you.

Vuforia Engine Support