Why am I getting a null reference exception error?

Taran

When I play my scene I receive this error (at this point I haven't connected/attempted a connection to Photon) -

NullReferenceException : Object not set to an instance of an object. Photon.Pun.PhotonNetwork.AddCallbackTarget (System.Object target) (at Assets/Photon/PhotonUnityNetworking/Code/PhotonNetworkPart.cs:85)

This error is stopping me from connecting to photon. Anyone know how I can fix this?

JohnTube

Hi @Taran,

Thank you for choosing Photon!

What PUN version do you use?
What is the full stack trace of the error?
What are the minimal repro steps? could you post a short snippet of where or how you use AddCallbackTarget?

Taran

Hi @JohnTube,

I am using PUN2. Regarding the error, I have noticed that it occurs every other time I play the scene. So I can play the scene and the error doesn't appear and I can connect to photon and everything seem to be working fine. Then the next time I play the scene the error appears and I cannot connect. This process seem to repeat itself infinitely. The code/error for the AddCallbackTarget isn't in any of my created scripts but is coming from PhotonNetworkPart (script which has come with Photon). Here is the code snippet from that script:

public static void AddCallbackTarget(object target)
{
if (target is PhotonView)
{
return;
}

IPunOwnershipCallbacks punOwnershipCallback = target as IPunOwnershipCallbacks;
if (punOwnershipCallback != null)
{
OnOwnershipRequestEv += punOwnershipCallback.OnOwnershipRequest;
OnOwnershipTransferedEv += punOwnershipCallback.OnOwnershipTransfered;
}

NetworkingClient.AddCallbackTarget(target);
}

Believe this is the full stack trace of the error:

NullReferenceException: Object reference not set to an instance of an object
Photon.Pun.PhotonNetwork.AddCallbackTarget (System.Object target) (at Assets/Photon/PhotonUnityNetworking/Code/PhotonNetworkPart.cs:85)
Photon.Pun.MonoBehaviourPunCallbacks.OnEnable () (at Assets/Photon/PhotonUnityNetworking/Code/PunClasses.cs:225)

What do you mean by the minimal repro steps?

JohnTube

hi @Taran,

You have a class that is extending MonoBehaviourPunCallbacks.
Somehow that component is being destroyed in Awake before OnEnable?

Taran

Okay. The class I have which extends MonoBehaviorPunCallbacks doesn't call the awake method (and neither does any other class within my scene) so that's a bit strange. I am going to move my script into a new clean project will only PUN2 downloaded and see whether or not the issue still persists.

JohnTube

I see the issue now.
First time we get such report.

PhotonNework.NetworkingClient is still null when PhotonNetwork.AddCallbackTarget is called which is not expected as the NetworkingClient is set in the constructor when the singleton instance is first created.
We will investigate.

Thanks for your report and patience!

albo

Hi! I've started to have same issue after I've switched to Compute Engine VM (not sure is that related)

NullReferenceException: Object reference not set to an instance of an object
Photon.Pun.PhotonNetwork.AddCallbackTarget (System.Object target) (at Assets/Photon/PhotonUnityNetworking/Code/PhotonNetworkPart.cs:85)
Photon.Pun.MonoBehaviourPunCallbacks.OnEnable () (at Assets/Photon/PhotonUnityNetworking/Code/PunClasses.cs:225)
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)

I've also updated Pun2 asset to the latest version. My class extending MonoBehaviourPunCallbacks and here the Start method

void Start()
        {
            if (!PhotonNetwork.IsConnected)
            {
                PhotonNetwork.AutomaticallySyncScene = true;
                PhotonNetwork.GameVersion = gameVersion;
                PhotonNetwork.ConnectUsingSettings();
            }

            Debug.Log(PhotonNetwork.LocalPlayer.UserId + " pid in start");
            progressLabel.SetActive(false);
            //controlPanel.SetActive(true);
        }

albo

In additional to that I have this error as well

NullReferenceException: Object reference not set to an instance of an object
Photon.Pun.PhotonNetwork.set_GameVersion (System.String value) (at Assets/Photon/PhotonUnityNetworking/Code/PhotonNetwork.cs:87)
Launcher.Start () (at Assets/Scripts/Launcher.cs:98)

where Launcher.cs:98 is

PhotonNetwork.GameVersion = gameVersion;

from start method

Tobias

@albo , @Taran , which version of Unity is that?
Any other exceptions in the logs? Please send a full log and the full class, which causes the error. So we can maybe repro.
You can mail us: developer@exitgames.com

doug_h

Taran wrote: »

Hi @JohnTube,

I am using PUN2. Regarding the error, I have noticed that it occurs every other time I play the scene. So I can play the scene and the error doesn't appear and I can connect to photon and everything seem to be working fine. Then the next time I play the scene the error appears and I cannot connect. This process seem to repeat itself infinitely. The code/error for the AddCallbackTarget isn't in any of my created scripts but is coming from PhotonNetworkPart (script which has come with Photon). Here is the code snippet from that script:

public static void AddCallbackTarget(object target)
{
if (target is PhotonView)
{
return;
}

IPunOwnershipCallbacks punOwnershipCallback = target as IPunOwnershipCallbacks;
if (punOwnershipCallback != null)
{
OnOwnershipRequestEv += punOwnershipCallback.OnOwnershipRequest;
OnOwnershipTransferedEv += punOwnershipCallback.OnOwnershipTransfered;
}

NetworkingClient.AddCallbackTarget(target);
}

Believe this is the full stack trace of the error:

NullReferenceException: Object reference not set to an instance of an object
Photon.Pun.PhotonNetwork.AddCallbackTarget (System.Object target) (at Assets/Photon/PhotonUnityNetworking/Code/PhotonNetworkPart.cs:85)
Photon.Pun.MonoBehaviourPunCallbacks.OnEnable () (at Assets/Photon/PhotonUnityNetworking/Code/PunClasses.cs:225)

What do you mean by the minimal repro steps?

This has just happened to me as well - updated to the latest version of PUN2 and every other time I hit play I get the same null reference exception. Occurred on both 2019.3.3f1 and 2019.3.12.f1.

I rolled back to the old package and the issue immediately went away. I have a very basic setup integrating PlayFab authentication (pretty much just followed the tutorials).

I will stay on the old version for now but thought you may be interested to know it is still occurring.

Cheers.

Tobias

@doug_h, I thought a colleague would reply. Yes, we are interested in this.
We could use a repro (via download link to developer@photonengine.com), so if you could share a project or such, we'd have a look. So far, we could not narrow it down.

Tobias

Did you disable "Domain Reloading" maybe?
https://docs.unity3d.com/Manual/DomainReloading.html

Tobias

@doug_h , @albo, I did not find a way to repro this yet, so we release PUN 2.19 without any fixes for this.

If you run into this again, it would help a lot if you could get us the full error logs and a repro case. Mail to: developer@photonengine.com to send a link to a project that reproduces it.

inventonater

Tobias wrote: »

Did you disable "Domain Reloading" maybe?
https://docs.unity3d.com/Manual/DomainReloading.html

Thank god for this post - Domain Reloading was exactly the problem for me. Was so confused why everytime I created a new project the issue wouldn't exist.. but in my real project it would break.. it was because I disabled Domain Reloading!