NullReference Error

Unity Courses Ask
#1

The error points to this line within the PlayerConversant.cs:
else
{ return currentConversant.GetName();
}

image
image1920×1080 391 KB

AIConversant.cs

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

namespace RPG.Dialogue
{
public class AIConversant : MonoBehaviour
{    
[SerializeField] Dialogue dialogue = null;
[SerializeField] Transform playerController;
[SerializeField] string conversantName;

public string GetName()
{

      return conversantName;
    }
private void Update() 
{
   float distance = Vector3.Distance(transform.position, playerController.position);
    if (distance <= 7f)
      {           
        if(Input.GetKeyDown(KeyCode.E))
        {        
           playerController.GetComponent<PlayerConversant>().StartDialogue(dialogue);
        }
      }
  
    }
    
  }
}

DialogueUI.cs

�using System.Collections;

using System.Collections.Generic;

using UnityEngine;

using RPG.Dialogue;

using TMPro;

using UnityEngine.UI;

namespace RPG.UI

{

    public class DialogueUI : MonoBehaviour

    {

        PlayerConversant playerConversant;

        [SerializeField] TextMeshProUGUI AIText;

        [SerializeField] Button nextButton;

        [SerializeField] GameObject AIResponse;

        [SerializeField] Transform choiceRoot;

        [SerializeField] GameObject choicePrefab;

        [SerializeField] Button quitButton;

        [SerializeField] TextMeshProUGUI conversantName;

        // Start is called before the first frame update

        void Start()

        {

            playerConversant = GameObject.FindGameObjectWithTag("Player").GetComponent<PlayerConversant>();

            playerConversant.onConversationUpdated += UpdateUI;

            nextButton.onClick.AddListener(() => playerConversant.Next());

            quitButton.onClick.AddListener(() => playerConversant.Quit());

            UpdateUI();

        }

       

        void UpdateUI()

        {

            gameObject.SetActive(playerConversant.IsActive());

            if (!playerConversant.IsActive())

            {

                return;

            }

            conversantName.text = playerConversant.GetCurrentConversantName();

            AIResponse.SetActive(true);

            choiceRoot.gameObject.SetActive(playerConversant.IsChoosing());

            if (playerConversant.IsChoosing())

            {

                BuildChoiceList();

                nextButton.gameObject.SetActive(!playerConversant.HasNext());

            }

            else

            {

                AIText.text = playerConversant.GetText();

                nextButton.gameObject.SetActive(playerConversant.HasNext());

            }

        }

        private void BuildChoiceList()

        {

            choiceRoot.DetachChildren();

            foreach (DialogueNode choice in playerConversant.GetChoices())

            {

                GameObject choiceInstance = Instantiate(choicePrefab, choiceRoot);

                var textComp = choiceInstance.GetComponentInChildren<TextMeshProUGUI>();

                textComp.text = choice.GetText();

                Button button = choiceInstance.GetComponentInChildren<Button>();

                button.onClick.AddListener(() =>

                {

                    playerConversant.SelectChoice(choice);

                });

            }

        }

    }

}

PlayerConversant.cs

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using UnityEngine;

namespace RPG.Dialogue
{
    public class PlayerConversant : MonoBehaviour
    {
        [SerializeField] string playerName;
        AIConversant currentConversant;
        Dialogue currentDialogue;
        DialogueNode currentNode = null;
        bool isChoosing = false;

        public event Action onConversationUpdated;

        
        public void StartDialogue(Dialogue newDialogue)
        {
            currentDialogue = newDialogue;
            currentNode = currentDialogue.GetRootNode();
            onConversationUpdated();
        }
        public void Quit()
        {
            currentDialogue = null;
            currentNode = null;
            isChoosing = false;
            onConversationUpdated();

        }

        public bool IsActive()
        {
            return currentDialogue != null;
        }

        public bool IsChoosing()
        {
            return isChoosing;
        }

        public string GetText()
        {
            if (currentNode == null)
            {
                return "";
            }

            return currentNode.GetText();
        }

        public IEnumerable<DialogueNode> GetChoices()
        {
            return currentDialogue.GetPlayerChilren(currentNode);
        }

        public void SelectChoice(DialogueNode chosenNode)
        {
            currentNode = chosenNode;
            isChoosing = false;
            Next();
        }

         public string GetCurrentConversantName()
        {
            if (isChoosing)
            {
                return playerName;
            }
            else
            {
                return currentConversant.GetName();
            }
        }

        public void Next()
        {
            int numPlayerResponses = currentDialogue.GetPlayerChilren(currentNode).Count();
            if (numPlayerResponses > 0)
            {
                isChoosing = true;
                onConversationUpdated();
                return;
            }

            DialogueNode[] children = currentDialogue.GetAIChildren(currentNode).ToArray();
            int randomIndex = UnityEngine.Random.Range(0, children.Count());
            currentNode = children[randomIndex];
            onConversationUpdated();
        }

        public bool HasNext()
        {
            return currentDialogue.GetAllChildren(currentNode).Count() > 0;
        }

        
    }
}

Ive assigned the names to the NPC and the Player and assigned the currentspeaker to the dialogue field.

#2

You’re not assigning the currentConversant.

StartDialogue needs to have a reference to the conversant in the header and then set it in the method

        public void StartDialogue(AIConversant newConversant, Dialogue newDialogue)
        {
            currentConversant = newConversant;
            //rest of the method

This also means that in AIConversant in the HandleRaycast method, you’ll need to pass the conversant to the StartDialogue method

callingController.GetComponent<PlayerConversant>().StartDialogue(this, dialogue);
#3

thank you that solves that issue, I encountered a different issue (not related to this lecture) when I finish a dialogue (clicking the last dialogue node within a dialogue while playing the game).

array error maybe
array error maybe1920×1080 322 KB 

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using UnityEngine;

namespace RPG.Dialogue
{
    public class PlayerConversant : MonoBehaviour
    {
        [SerializeField] string playerName;

        Dialogue currentDialogue;
        DialogueNode currentNode = null;
        AIConversant currentConversant = null;
        bool isChoosing = false;

        public event Action onConversationUpdated;

        public void StartDialogue(AIConversant newConversant, Dialogue newDialogue)
        {
            currentConversant = newConversant;
            currentDialogue = newDialogue;
            currentNode = currentDialogue.GetRootNode();
            
            onConversationUpdated();
        }

        public void Quit()
        {
            currentDialogue = null;
            
            currentNode = null;
            isChoosing = false;
            currentConversant = null;
            onConversationUpdated();
        }

        public bool IsActive()
        {
            return currentDialogue != null;
        }

        public bool IsChoosing()
        {
            return isChoosing;
        }

        public string GetText()
        {
            if (currentNode == null)
            {
                return "";
            }

            return currentNode.GetText();
        }

        public string GetCurrentConversantName()
        {
            if (isChoosing)
            {
                return playerName;
            }
            else
            {
                return currentConversant.GetName();
            }
        }

        public IEnumerable<DialogueNode> GetChoices()
        {
            return currentDialogue.GetPlayerChilren(currentNode);
        }

        public void SelectChoice(DialogueNode chosenNode)
        {
            currentNode = chosenNode;
            
            isChoosing = false;
            Next();
        }
    
        public void Next()
        {
            int numPlayerResponses = currentDialogue.GetPlayerChilren(currentNode).Count();
            if (numPlayerResponses > 0)
            {
                isChoosing = true;
                
                onConversationUpdated();
                return;
            }

            DialogueNode[] children = currentDialogue.GetAIChildren(currentNode).ToArray();
            int randomIndex = UnityEngine.Random.Range(0, children.Count());
            
            currentNode = children[randomIndex];
            
            onConversationUpdated();
        }

        public bool HasNext()
        {
            return currentDialogue.GetAllChildren(currentNode).Count() > 0;
        }

        
    }
}

Is there an error with the array or something?

#4

The error is here. If there are no children, the array will have 0 elements and the Random.Range() will return 0. This is the first element, but there is no first element.

You need to check if anything returned from GetAIChildren

#5

thanks!

#6

If there are children on the current node, but they are all filtered away, then HasNext() will be true, but the children array will be empty, tricking the system.
A simple check manages this

if(children.Length>0)
{   
     currentNode = children[randomIndex];
}
1 Like
#7

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