How to fix NullReferenceException: Object reference not set to an instance of an object error

Questions & Answers
1

I am working on an inventory and every time I opne it I get this error: NullReferenceException: Object reference not set to an instance of an object
Inventory.LoadUnloadInventoryMenu () (at Assets/Scripts/Inventory.cs:116)
Inventory.Update () (at Assets/Scripts/Inventory.cs:59)

This is the inventory.cs script:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;

public class Inventory : MonoBehaviour
{
	//Keys used to open doors
	public bool hasRedKey, hasGreenKey, hasBlueKey;

	//the item the player is using
	public Sprite mainItem;

	public Sprite[] hotbar = new Sprite[3];


	//every item in the game
	public Sprite[] items = new Sprite[30];


	//items in the players inventory
	public Sprite[] inventory = new Sprite[20];

	//armor slots in thye players Inventory
	public Sprite[] armor = new Sprite[4];

	//the inventory menu
	public GameObject menu;

	void Start()
	{
		//Deactivating the menu
		menu.SetActive(false);

		//assinging values
		mainItem = items[0];
		FindObjectOfType<CanvasManager>().UpdateMainItem(mainItem);
		hotbar[0] = items[3];
		hotbar[1] = items[20];
		hotbar[2] = items[4];
		FindObjectOfType<CanvasManager>().UpdateHotbar(hotbar);

		for(int i = 0; i < 20; i++)
		{
			inventory _= items*;*_

* }*

* for (int i = 0; i < 4; i++)*
* {*
armor = items*;*
* }*
* }*

* void Update()*
* {*
* //checking if the player opened/ closed the inventory*
* if (Input.GetKeyDown(KeyCode.E))*
* {*
* LoadUnloadInventoryMenu();*
* }*

* //cycle through hotbar*
* if (Input.mouseScrollDelta.y == 1)*
* {*
* nextItem();*
* }*

* if (Input.mouseScrollDelta.y == -1)*
* {*
* prevItem();*
* }*
* }*

* private void nextItem()*
* {*
* Sprite temp = hotbar[0];*
* hotbar[0] = hotbar[1];*
* hotbar[1] = hotbar[2];*
* hotbar[2] = mainItem;*
* mainItem = temp;*
* FindObjectOfType().UpdateHotbar(hotbar);*
* FindObjectOfType().UpdateMainItem(mainItem);*

* }*

* private void prevItem()*
* {*
* Sprite temp = mainItem;*
* mainItem = hotbar[2];*
* hotbar[2] = hotbar[1];*
* hotbar[1] = hotbar[0];*
* hotbar[0] = temp;*
* FindObjectOfType().UpdateHotbar(hotbar);*
* FindObjectOfType().UpdateMainItem(mainItem);*
* }*

* private void LoadUnloadInventoryMenu()*
* {*
* if (menu.activeSelf)*
* {*
* //diactivatting the inventory when its open*
* menu.SetActive(false);*
* }*
* else*
* {*
* //activatting the inventory*
* menu.SetActive(true);*

* //null check*
* if(inventory != null && armor != null && hotbar != null)*
* {*

* //update the items to the correct value*
* GameObject.Find(“InventoryManager”).GetComponent().UpdateInventory();*
* GameObject.Find(“InventoryManager”).GetComponent().UpdateHotbar();*
* GameObject.Find(“InventoryManager”).GetComponent().UpdateArmor();*

* }*

* }*

* }*
}
The Canvas manager is used to display the UI visible throughout the game that displays things like health to the player. The “menu” object I assigned manually in the Unity Inspector as the InventoryManager object which is the InventoryUI.
This is the InventoryManager.cs file:
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;

public class InventoryManager : MonoBehaviour
{
* //definning inventory slots*
* public Image[] inventory = new Image[20];*
* public Image[] armor = new Image[4];*
* public Image[] hotbar = new Image[3];*

* //setting the hotbar slots to the correct values*
* public void UpdateHotbar()*
* {*
* Sprite[] toLoad = GameObject.Find(“Inventory”).GetComponent().hotbar;*

* for(int i = 0; i < hotbar.Length; i++)*
{
hotbar_.sprite = toLoad*;
}
}*_

* //setting the armor slots to the correct values*
* public void UpdateArmor()*
* {*
* Sprite[] toLoad = GameObject.Find(“Inventory”).GetComponent().armor;*

* for(int i = 0;i < armor.Length; i++)*
{
_ armor*.sprite = toLoad[0];
}
}*_

* //setting the inventory slots to the correct values*
* public void UpdateInventory()*
* {*
* Sprite[] toLoad = GameObject.Find(“Inventory”).GetComponent().inventory;*

* for (int i = 0; i < inventory.Length; i++)*
* {*
_ inventory*.sprite = toLoad[0];
}
}
}*_

If anyone knows why I’m getting this error please let me know.
Thanks in advance.

2

This error might be showing because (A) you haven’t set the GameObject with the InventoryManager name to “InventoryManager” correctly or (B) it has the correct name but the script is not attached to it.

A better way to solve this might be using Singletons. Singletons allow certain classes to be accessible everywhere in the game. You can learn more about Singletons here.

In any case, if you decide to move on with the GameObject.Find or the GetComponent a better way of doing it is by keeping a reference to the object or the component the first time you look for it and then access directly through that reference like:

//update the items to the correct value
InventoryManager inventoryManager = GameObject.Find("InventoryManager").GetComponent<InventoryManager>();
if(inventoryManager != null)
{
        inventoryManager.UpdateInventory();
        inventoryManager.UpdateHotbar();
        inventoryManager.UpdateArmor();
}