I have a nullreferenceexception error in my unity survival game

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I am having a Null error that I cannot figure out how to solve, unlike my other Null errors. The error in the Unity console states

"NullReferenceException: Object reference not set to an instance of an object
Inventory.ClearSelectedItemWindow () (at Assets/Scripts/Player/Inventory.cs:202)
Inventory.Start () (at Assets/Scripts/Player/Inventory.cs:62)"

with another error under it reading

"NullReferenceException while executing 'started' callbacks of 'Main/Inventory[/Keyboard/q]'
UnityEngine.InputSystem.LowLevel.NativeInputRuntime/<>c__DisplayClass7_0:<set_onupdate>b__0 (UnityEngineInternal.Input.NativeInputUpdateType,UnityEngineInternal.Input.NativeInputEventBuffer*)
UnityEngineInternal.Input.NativeInputSystem:NotifyUpdate (UnityEngineInternal.Input.NativeInputUpdateType,intptr)"

The console says the error is on line 202 in my Inventory script.

C++

void ClearSelectedItemWindow ()
    {
        // clear the text elements
        selectedItem = null;
        selectedItemName.text = string.Empty;
        selectedItemDescription.text = string.Empty;
        selectedItemStatNames.text = string.Empty;
        selectedItemStatValues.text = string.Empty;

        // disable buttons
        useButton.SetActive(false);
        equipButton.SetActive(false);
        unEquipButton.SetActive(false);
        dropButton.SetActive(false);
    }



which is connected to the full script here



public void SelectItem (int index)
    {
        if(slots[index].item == null)
            return;


        selectedItem = slots[index];
        selectedItemIndex = index;

        selectedItemName.text = selectedItem.item.displayName;
        selectedItemDescription.text = selectedItem.item.description;

        // set stat values and stat names
        selectedItemStatNames.text = string.Empty;
        selectedItemStatValues.text = string.Empty;

        for(int x = 0; x < selectedItem.item.consumables.Length; x++)
        {
            selectedItemStatNames.text += selectedItem.item.consumables[x].type.ToString() + "\n";
            selectedItemStatValues.text += selectedItem.item.consumables[x].value.ToString() + "\n";

        }

        useButton.SetActive(selectedItem.item.type == ItemType.Consumable);
        equipButton.SetActive(selectedItem.item.type == ItemType.Equipable && !uiSlots[index].equipped);
        unEquipButton.SetActive(selectedItem.item.type == ItemType.Equipable && uiSlots[index].equipped);
        dropButton.SetActive(true);
    }

    void ClearSelectedItemWindow ()
    {
        // clear the text elements
        selectedItem = null;
        selectedItemName.text = string.Empty;
        selectedItemDescription.text = string.Empty;
        selectedItemStatNames.text = string.Empty;
        selectedItemStatValues.text = string.Empty;

        // disable buttons
        useButton.SetActive(false);
        equipButton.SetActive(false);
        unEquipButton.SetActive(false);
        dropButton.SetActive(false);
    }

    public void OnUseButton ()
    {
        if(selectedItem.item.type == ItemType.Consumable)
        {
            for(int x = 0; x < selectedItem.item.consumables.Length; x++)
            {
                switch(selectedItem.item.consumables[x].type)
                {
                    case ConsumableType.Health: needs.Heal(selectedItem.item.consumables[x].value); break;
                    case ConsumableType.Hunger: needs.Eat(selectedItem.item.consumables[x].value); break;
                    case ConsumableType.Thirst: needs.Drink(selectedItem.item.consumables[x].value); break;
                    case ConsumableType.Sleep: needs.Sleep(selectedItem.item.consumables[x].value); break;
                }
            }
        }

If you have any idea why the error is happening or need more of my inventory script please get back to me.

What I have tried:

I have tried every other common method I use to fix the Null errors but none of them are working or helping me out this time.

Posted 24-May-21 15:14pm

Blake Burnell

Updated 24-May-21 20:12pm

CPallini

v2

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[no name] 24-May-21 23:16pm

Which is line "202"? How are we supposed to know? Have you "stepped" through your code (debug) and examined line 202?

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OriginalGriff · Accepted Answer · 2021-05-24T19:52:00

This is one of the most common problems we get asked, and it's also the one we are least equipped to answer, but you are most equipped to answer yourself.

Let me just explain what the error means: You have tried to use a variable, property, or a method return value but it contains null - which means that there is no instance of a class in the variable.
It's a bit like a pocket: you have a pocket in your shirt, which you use to hold a pen. If you reach into the pocket and find there isn't a pen there, you can't sign your name on a piece of paper - and you will get very funny looks if you try! The empty pocket is giving you a null value (no pen here!) so you can't do anything that you would normally do once you retrieved your pen. Why is it empty? That's the question - it may be that you forgot to pick up your pen when you left the house this morning, or possibly you left the pen in the pocket of yesterday's shirt when you took it off last night.

We can't tell, because we weren't there, and even more importantly, we can't even see your shirt, much less what is in the pocket!

Back to computers, and you have done the same thing, somehow - and we can't see your code, much less run it and find out what contains null when it shouldn't.
But you can - and Visual Studio will help you here. Run your program in the debugger and when it fails, VS will show you the line it found the problem on. You can then start looking at the various parts of it to see what value is null and start looking back through your code to find out why. So put a breakpoint at the beginning of the method containing the error line, and run your program from the start again. This time, VS will stop before the error, and let you examine what is going on by stepping through the code looking at your values.

But we can't do that - we don't have your code, we don't know how to use it if we did have it, we don't have your data. So try it - and see how much information you can find out!