I have a same problem in unity. but if you try to make a GUI button in sample app and if you don't make your own scene then you will not get any NullReference error.

Glad to hear that the article was helpful to solve your problem.

And, thanks, we will keep the suggestion about Video Playback vanilla example / tutorial in consideration.

Cheers.

Sorry, hadn't seen that yet. 

Will do and report back, thanks! 

Edit: works! 

At first I had two errors (around IEnumerable<Trackable>), but I had to change the standard using System.Collections; to using System.Collections.Generic; and add a closing } at the end of the script. 

And just to be sure, it's not unsafe/unstable or anything if I set the BuildNewTarget function to public? 

Thanks again!

P.s. if we could have a similar vanilla example of the video texture, that'd be awesome!

Check this article, which explains step by step what you need to setup UDT correctly:

https://developer.vuforia.com/forum/faq/unity-how-do-i-create-simple-udt-app

try to compare your setup with the one abpve, to see if you have missed anything.

Hi, 

I have a similar set-up and the same issue (don't want to clog up the forums with duplicate questions). 

I'm using (or: trying to use) an NGUI button to trigger a new UDT. These are the steps I followed: 

1. Applied the UserDefinedTargetEventHandler script from the sample to the UserDefinedTargetBuilder object. 
2. Commented out some of the UI stuff that I don't need (e.g. Draw() and mNewUserDefinedTargetButton).
3. Added an image target and referenced it from the UserDefinedTargetBuilder.
4. Made the UserDefinedTargetEventHandler => BuildNewTarget() function public.
5. Put a script on my NGUI element to call this function using public UserDefinedTargetEventHandler builder => builder.BuildNewTarget();

The nullReference error occurs on the line mTargetBuildingBehaviour.BuildNewTarget(targetName, ImageTargetTemplate.GetSize().x);

Which looks like it can't find the image target? 

I've attached two screenshots of the links between the button, builder and target. 

Any help would be appreciated. 

Thanks

I've already seen it, but I have not been of help. is an error that appears to me as I push the button to set the new targets

Have you checked the Getting started guide?

This explains how to setup Vuforia and the samples:

https://developer.vuforia.com/resources/dev-guide/getting-started-unity-extension

Note: you need Unity 4.1 or higher (just in case).