Issue with Door Opening Script - Teleportation and Null Object Error

Unity Engine
,
1

Hello Unity community,

I’m currently facing some difficulties with my door opening script. The script worked perfectly until I tried using it in a new room setup. Initially, the door used to teleport slightly, but after reimporting the door asset, the script stopped functioning altogether. When I try to run the game, the console displays an error message stating “object at index 0 is null.”

Problem:

  • Teleportation: Previously, the door would teleport a bit when opening, which was not the intended behavior. I would like the door to open smoothly without any teleportation.

  • Null Object Error: After reimporting the door asset into a new room, the door opening script no longer works. The console shows an error message mentioning “object at index 0 is null,” but I’m unsure why this error occurs.

Code:

using UnityEngine;

public class DoorScript : MonoBehaviour
{
    public Transform PlayerCamera;
    [Header("MaxDistance you can open or close the door.")]
    public float MaxDistance = 5;

    private bool opened = false;
    private Animator anim;



    void Update()
    {
        if (Input.GetKeyDown(KeyCode.E))
        {
            Pressed();

        }
    }

    void Pressed()
    {
        Debug.Log("1");
        RaycastHit doorhit;

        if (Physics.Raycast(PlayerCamera.transform.position, PlayerCamera.transform.forward, out doorhit, MaxDistance))
        {
            Debug.Log("2");

            if (doorhit.transform.tag == "Door")
            {
                Debug.Log("3");
               
                anim = doorhit.transform.GetComponent<Animator>();

               
                opened = !opened;

               
                anim.SetBool("Opened", !opened);
            }
        }
    }
}

I kindly request your assistance in identifying the reasons behind the teleportation issue and the null object error in my door opening script. Any insights or suggestions you can provide to help resolve these problems would be greatly appreciated.

Thank you in advance for your support and expertise!

Best regards

2

The answer is always the same… ALWAYS!

How to fix a NullReferenceException error

https://forum.unity.com/threads/how-to-fix-a-nullreferenceexception-error.1230297/

Three steps to success:

  • Identify what is null ← any other action taken before this step is WASTED TIME
  • Identify why it is null
  • Fix that

Time to start debugging! Here is how you can begin your exciting new debugging adventures:

You must find a way to get the information you need in order to reason about what the problem is.

Once you understand what the problem is, you may begin to reason about a solution to the problem.

What is often happening in these cases is one of the following:

  • the code you think is executing is not actually executing at all
  • the code is executing far EARLIER or LATER than you think
  • the code is executing far LESS OFTEN than you think
  • the code is executing far MORE OFTEN than you think
  • the code is executing on another GameObject than you think it is
  • you’re getting an error or warning and you haven’t noticed it in the console window

To help gain more insight into your problem, I recommend liberally sprinkling Debug.Log() statements through your code to display information in realtime.

Doing this should help you answer these types of questions:

  • is this code even running? which parts are running? how often does it run? what order does it run in?
  • what are the names of the GameObjects or Components involved?
  • what are the values of the variables involved? Are they initialized? Are the values reasonable?
  • are you meeting ALL the requirements to receive callbacks such as triggers / colliders (review the documentation)

Knowing this information will help you reason about the behavior you are seeing.

You can also supply a second argument to Debug.Log() and when you click the message, it will highlight the object in scene, such as Debug.Log("Problem!",this);

If your problem would benefit from in-scene or in-game visualization, Debug.DrawRay() or Debug.DrawLine() can help you visualize things like rays (used in raycasting) or distances.

You can also call Debug.Break() to pause the Editor when certain interesting pieces of code run, and then study the scene manually, looking for all the parts, where they are, what scripts are on them, etc.

You can also call GameObject.CreatePrimitive() to emplace debug-marker-ish objects in the scene at runtime.

You could also just display various important quantities in UI Text elements to watch them change as you play the game.

Visit Google for how to see console output from builds. If you are running a mobile device you can also view the console output. Google for how on your particular mobile target, such as this answer for iOS: How To - Capturing Device Logs on iOS or this answer for Android: How To - Capturing Device Logs on Android

If you are working in VR, it might be useful to make your on onscreen log output, or integrate one from the asset store, so you can see what is happening as you operate your software.

Another useful approach is to temporarily strip out everything besides what is necessary to prove your issue. This can simplify and isolate compounding effects of other items in your scene or prefab.

If your problem is with OnCollision-type functions, print the name of what is passed in!

Here’s an example of putting in a laser-focused Debug.Log() and how that can save you a TON of time wallowing around speculating what might be going wrong:

“When in doubt, print it out!™” - Kurt Dekker (and many others)

Note: the print() function is an alias for Debug.Log() provided by the MonoBehaviour class.

3

After the error message you should see two numbers in parentheses. The first number tells you the line number where the error occurred. The second number tells you which column. Given that, it should be easy to find the object that is null.