Resolved NullReferenceException Warning for GameObjects

Hello Dear Unity Community,

There are too many explainings about NullReferenceObjects, but I could not fix it yet.

I have defined my GameObjects variables as public, and drag&drop Objects to inspector panel like this

Code (CSharp):

1.  
2.  
3. public class scalescript : MonoBehaviour
4. {
5.  
6.     public int Kontrol;
7.     public float AnlikBoyutx, AnlikBoyuty, IstenenBoyutx, IstenenBoyuty;
8.     public Vector3 vector;
9.     public Vector3 Istenenvector;
10.     public GameObject nesne;
11.     public int ZoomSpeed = 8;
12.  
13.     public GameObject Buton_Play;
14.     public GameObject ButtonDown;
15.     public GameObject ButtonUp;
16.     public GameObject Canvas_Buton;
17.  
18.     void Start()
19.     {
20.         Kontrol = 3;
21.         Canvas_Buton = GameObject.Find("CanvasButon");
22.         Buton_Play = GameObject.Find("PlayButonu");
23.         ButtonDown = GameObject.Find("Button_Down");
24.         ButtonUp = GameObject.Find("Button_Up");
25.         nesne =  GameObject.Find("Quad_Video5");
26.         vector = GameObject.Find("Quad_Video5").GetComponent<Transform>().localScale;
27.      }
28.  

This is scalescript code which has NullReferenceException warning:

Code (CSharp):

1. public void TargetLost()
2.     {
3.         ButtonUp.gameObject.SetActive(false);  //its ok
4.         ButtonDown.gameObject.SetActive(false); //has NullReferenceException error
5.  
6.         nesne.transform.localScale = vector; //Its ok
7.         GameObject.Find("Quad_Video5").gameObject.GetComponent<VideoPlayer>().Stop(); //Its ok
8.     }
9.  
10.     public void TargetFind()
11.     {
12.         Buton_Play.gameObject.SetActive(true); //Its ok
13.         ButtonUp.gameObject.SetActive(true); //has NullReferenceException error
14.     }

This my objects on scene


This is Inspector Panel QuadVideo5 and ScaleScript


This is Error:


Why ı see this NullException Warning? Could you help me please...

Thank you...

 

It looks to me like you are manually setting the public gameobjects via the Inspector but you're also setting them in the Start method via GameObject.Find. GameObject.Find only returns active objects though, and from the screenshot of your hierarchy it looks like the objects are disabled.

Removing these lines should fix the error:

ButtonDown = GameObject.Find("Button_Down");

ButtonUp = GameObject.Find("Button_Up");

 

Or you can start the scene with those objects active and disable them within the script after the references have been set.

As a side note, if you are setting all the public gameobjects in the inspector there's no need for any of the lines using GameObject.Find. I've seen many posts recommending that you avoid using that method at all if possible. In particular the line:

vector = GameObject.Find("Quad_Video5").GetComponent<Transform>().localScale;

should be simplified to:

vector = nesne.GetComponent<Transform>().localScale;

 

Thank you for your answer TuckerFlynn!! Yes theese objects have to be unvisible of passive. I understand that, You advise to me. Active all of them at first. But make passive with scripts. I'll try it.

But I dont understand that you said "GameObject.Find only returns active objects though."
Why I can not do any operation with passive object by using Game.Object?

Thanks for reply...

 

By the way. I have catch that;
Before TargetFind() function. My Inspector screen is like that:

But After TargetFind() fucntion is running, My Inspector screen is like that:

At the first Gameobjects are there. But when function run, it has gone..

 

You can do a lot of things with inactive GameObjects, it's just that Find is not one of the things you can do. GameObject.Find is bad to use in general - it's easy to learn and understand, but it's never the best thing to use in any particular situation. This article has a list of other options that are better than GameObject.Find for particular situations.

In this case, you almost certainly want to (as others have advised) simply remove the GameObject.Find lines and drag-to-assign all of the references instead.

 

Thank you Star Manta.

I have deleted these lines:

ButtonDown = GameObject.Find("Button_Down");
ButtonUp = GameObject.Find("Button_Up");

And it works!

But I want to understand why? Because The PlayButonu is work fine too. And There is public GameObject Buton_Play; code in my script. And I dragged drop to inspector this gameobject too. So Why this line not give an error? But other gameobjects give error? What is the point in this case. I want to learn it. Could you please explain me as simply?

Thanks.