New input system Null Reference Exception error

News & General Discussion
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1

Hello All,

I’m using the New Input handler and when my scene changes i’m getting the below error

NullReferenceException: Object reference not set to an instance of an object
PlayerInputHandler.OnDisable () (at Assets/Scripts/PlayerInputHandler.cs:73)
UnityEngine.Object:Destroy(Object)
PlayerInputHandler:Awake() (at Assets/Scripts/PlayerInputHandler.cs:40)

I’ve pinned it down to when i destroy the Handlers clone when a new level is loaded. So i remove the destroy command and the error disspaears. However, i then get a clone as i have the handler as do not destroy.

using System.Collections;
using System.Collections.Generic;
using UnityEditorInternal;
using UnityEngine;
using UnityEngine.InputSystem;

public class PlayerInputHandler : MonoBehaviour
{
    [Header("Input Action Asset")]
    [SerializeField] private InputActionAsset playerControls;

    [Header("Action Map Name Reference")]
    [SerializeField] private string actionMapName = "Player";

    [Header("Action Name Reference")]
    [SerializeField] private string move = "Move";
    [SerializeField] private string attack = "Attack";

    private InputAction moveAction;
    private InputAction attackAction;

    public Vector2 MoveInput { get; private set; }
    public bool AttackTriggered { get; private set; }
    private static PlayerInputHandler instance;
    public static PlayerInputHandler Instance
    {
        get
        {
            if (instance == null) instance = GameObject.FindObjectOfType<PlayerInputHandler>();
            return instance;

        }

    }

    private void Awake()
    {
        if(Player.Instance.level > 1)
        {
            if (GameObject.Find("PlayerInputHandler")) Destroy(gameObject);
        }
        
        moveAction = playerControls.FindActionMap(actionMapName).FindAction(move);
        attackAction = playerControls.FindActionMap(actionMapName).FindAction(attack);

        RegisterInputActions();
    }

    void Start()
    {
        DontDestroyOnLoad(gameObject);
    }

    void RegisterInputActions()
    {
        moveAction.performed += context => MoveInput = context.ReadValue<Vector2>();
        moveAction.canceled += context => MoveInput = Vector2.zero;

        attackAction.performed += context => AttackTriggered = true;
        attackAction.canceled += context => AttackTriggered = false;
    }

    private void OnEnable()
    {
        moveAction.Enable();
        attackAction.Enable();

        InputSystem.onDeviceChange += OnDeviceChange;
    }

    private void OnDisable()
    {
        moveAction.Disable();
        attackAction.Disable();

        InputSystem.onDeviceChange -= OnDeviceChange;
    }

    private void OnDeviceChange(InputDevice device, InputDeviceChange change)
    {
        switch (change) 
        {
            case InputDeviceChange.Disconnected:
                Debug.Log("Device Disconnected: " + device.name);
                break;
            case InputDeviceChange.Reconnected:
                Debug.Log("Device Reconnected: " + device.name);
                break;
        }
    }
}

So my question is do i remove the do not destroy and let each scene generate the handler or is there a better way to write this script?

Thanks in advance.

2

Generate the handler once and use DontDestroyOnLoad() instead of repeatedly destroying and recreating it. You just check if it’s already in the scene and, if so, don’t make a new one.