NullReferenceException, ARCamera

Unity Engine
1

Got a code from below, and exactly followed a youtube video. However, I wanted to test the code through the laptop cam. When I ran it, it displayed the following error:

NullReferenceException: Object reference not set to an instance of an object
ARPlacement.UpdatePlacementPose () (at Assets/Script/ARPlacement.cs:50)
ARPlacement.Update () (at Assets/Script/ARPlacement.cs:30)

Code is below:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.XR.ARFoundation;
using UnityEngine.XR.ARSubsystems;
public class ARPlacement : MonoBehaviour
{
public GameObject arObjectToSpawn;
public GameObject placementIndicator;
private GameObject spawnedObject;
private Pose PlacementPose;
private ARRaycastManager aRRaycastManager;
private bool placementPoseIsValid = false;
void Start()
{
aRRaycastManager = FindObjectOfType();
}
void Update()
{
if (spawnedObject == null && placementPoseIsValid && Input.touchCount > 0 && Input.GetTouch(0).phase == TouchPhase.Began)
{
ARPlaceObject();
}
UpdatePlacementPose();
UpdatePlacementIndicator();
}
void UpdatePlacementIndicator()
{
if (spawnedObject == null && placementPoseIsValid)
{
placementIndicator.SetActive(true);
placementIndicator.transform.SetPositionAndRotation(PlacementPose.position, PlacementPose.rotation);
}
else
{
placementIndicator.SetActive(false);
}
}
void UpdatePlacementPose()
{
var screenCenter = Camera.current.ViewportToScreenPoint(new Vector3(0.5f, 0.5f));
var hits = new List();
aRRaycastManager.Raycast(screenCenter, hits, TrackableType.Planes);
placementPoseIsValid = hits.Count > 0;
if (placementPoseIsValid)
{
PlacementPose = hits[0].pose;
}
}
void ARPlaceObject()
{
spawnedObject = Instantiate(arObjectToSpawn, PlacementPose.position, PlacementPose.rotation);
}
}

2

Code is never needed for a null reference and neither is a forum post. Why?

The answer is always the same… ALWAYS. It is the single most common error ever.

Don’t waste your life spinning around and round on this error. Instead, learn how to fix it fast… it’s EASY!!

Some notes on how to fix a NullReferenceException error in Unity3D

  • also known as: Unassigned Reference Exception
  • also known as: Missing Reference Exception
  • also known as: Object reference not set to an instance of an object

http://plbm.com/?p=221

The basic steps outlined above are:

  • Identify what is null
  • Identify why it is null
  • Fix that.

Expect to see this error a LOT. It’s easily the most common thing to do when working. Learn how to fix it rapidly. It’s easy. See the above link for more tips.

You need to figure out HOW that variable is supposed to get its initial value. There are many ways in Unity. In order of likelihood, it might be ONE of the following:

  • drag it in using the inspector
  • code inside this script initializes it
  • some OTHER external code initializes it
  • ? something else?

This is the kind of mindset and thinking process you need to bring to this problem:

https://discussions.unity.com/t/814091/4

Step by step, break it down, find the problem.

Here is a clean analogy of the actual underlying problem of a null reference exception:

https://discussions.unity.com/t/840647/7