[Part 14] MissingReferenceException with RectTransform

[Kim Il Woo (FGW HCM)]

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MissingReferenceException: The object of type 'UnityEngine.RectTransform' has been destroyed but you are still trying to access it.
Your script should either check if it is null or you should not destroy the object.
UnityEngine.Object+MarshalledUnityObject.TryThrowEditorNullExceptionObject (UnityEngine.Object unityObj, System.String parameterName) (at <c01a2e87500f4b88b40eba7308bfcbe6>:0)
UnityEngine.Bindings.ThrowHelper.ThrowNullReferenceException (System.Object obj) (at <c01a2e87500f4b88b40eba7308bfcbe6>:0)
UnityEngine.Transform.set_position (UnityEngine.Vector3 value) (at <c01a2e87500f4b88b40eba7308bfcbe6>:0)
GameManager+<GenerateFloatingTextCoroutine>d__31.MoveNext () (at Assets/Scripts/GameManager.cs:153)
UnityEngine.SetupCoroutine.InvokeMoveNext (System.Collections.IEnumerator enumerator, System.IntPtr returnValueAddress) (at <c01a2e87500f4b88b40eba7308bfcbe6>:0)
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr, Boolean&)

MissingReferenceException: The object of type 'UnityEngine.Transform' has been destroyed but you are still trying to access it.
Your script should either check if it is null or you should not destroy the object.
UnityEngine.Object+MarshalledUnityObject.TryThrowEditorNullExceptionObject (UnityEngine.Object unityObj, System.String parameterName) (at <c01a2e87500f4b88b40eba7308bfcbe6>:0)
UnityEngine.Bindings.ThrowHelper.ThrowNullReferenceException (System.Object obj) (at <c01a2e87500f4b88b40eba7308bfcbe6>:0)
UnityEngine.Transform.get_position () (at <c01a2e87500f4b88b40eba7308bfcbe6>:0)
GameManager+<GenerateFloatingTextCoroutine>d__31.MoveNext () (at Assets/Scripts/GameManager.cs:153)
UnityEngine.SetupCoroutine.InvokeMoveNext (System.Collections.IEnumerator enumerator, System.IntPtr returnValueAddress) (at <c01a2e87500f4b88b40eba7308bfcbe6>:0)
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr, Boolean&)

How can I fix this error it say something about the line 153 which is this line rect.position = referenceCamera.WorldToScreenPoint(target.position + new Vector3(0, yOffset));

[Terence]

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It is saying that your target variable is null, so target.position fails because it becomes null.position.

Can you share your entire script here?

[Alp Apustaja]

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Add null checks before accessing target and rect:

if (target != null && rect != null) {
    rect.position = referenceCamera.WorldToScreenPoint(target.position + new Vector3(0, yOffset));
}

This will prevent accessing destroyed objects and stop the MissingReferenceException.

• Terence

has upvoted this post.

[Kim Il Woo (FGW HCM)]

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Thanks for answering this error of mine but now im currently having error at part 15 which i have already posted in the forum

[Alp Apustaja]

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I can help you with that! Please provide the details of the error you’re encountering at part 15, along with any relevant code snippets. This way, I can better assist you in resolving the issue.

[Kim Il Woo (FGW HCM)]

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

public class GameManager : MonoBehaviour
{
    public static GameManager instance;
    //define different state of the game
    public enum GameState
    {
        Gameplay,
        Paused,
        GameOver,
        LeveUp
    }

    //store the current state of the game
    public GameState currentState;

    //store previous game state
    public GameState previouseState;

    [Header("Damage Text Setting")]
    public Canvas damageTextCanvas;
    public float textFontSize = 50;
    public TMP_FontAsset textFont;
    public Camera referenceCamera;

    [Header("Screens")]
    public GameObject pauseScreen;
    public GameObject resultsScreen;
    public GameObject levelUpScreen;
    int stackedLevelUps = 0;

    [Header("Current State Display")]
    public TMP_Text currentHealthDisplay;
    public TMP_Text currentRecoveryDisplay;
    public TMP_Text currentMoveSpeedDisplay;
    public TMP_Text currentMightDisplay;
    public TMP_Text currentProjectileSpeedDisplay;
    public TMP_Text currentMagnetDisplay;

    [Header("Results Screen Displays")]
    public Image chosenCharacterImage;
    public TMP_Text chosenCharacterName;
    public TMP_Text levelReachedDisplay;
    public TMP_Text timeSurviveDisplay;
    public List<Image> chosenWeaponsUI = new List<Image>(6);
    public List<Image> chosenPassiveItemsUI = new List<Image>(6);

    [Header("Stopwatch")]
    public float timeLimit;
    float stopwatchTime;
    public TMP_Text stopwatchDisplay;

    //refernce to the player object
    public GameObject playerObject;

    public bool isGameOver { get { return currentState == GameState.GameOver; } }
    public bool choosingUpgrade{get { return currentState == GameState.LeveUp; }}

    public float GetElapsedTime() { return stopwatchTime; }

    void Awake()
    {
        //warning to check if there is also a singleton of this kind in the game
        if (instance == null)
        {
            instance = this;
        }
        else
        {
            Debug.LogWarning("extra" + this + "deleted");
            Destroy(gameObject);
        }

        DisableScreen();
    }

    void Update()
    {

        switch (currentState)
        {
            case GameState.Gameplay:
                //code for gameplay state
                CheckForPauseAndResume();
                UpdateStopWatch();
                break;

            case GameState.Paused:
                //code for pause state
                CheckForPauseAndResume();
                break;

            case GameState.GameOver:
                //code for gameover state
                break;
            case GameState.LeveUp:
                break;

            default:
                Debug.LogWarning("State dont exist");
                break;
        }
    }

    IEnumerator GenerateFloatingTextCoroutine(string text, Transform target, float duration = 1f, float speed = 50f)
    {
        GameObject textObj = new GameObject("Damage Floating Text");
        RectTransform rect = textObj.AddComponent<RectTransform>();
        TextMeshProUGUI tmPro = textObj.AddComponent<TextMeshProUGUI>();
        tmPro.text = text;
        tmPro.horizontalAlignment = HorizontalAlignmentOptions.Center;
        tmPro.verticalAlignment = VerticalAlignmentOptions.Middle;
        tmPro.fontSize = textFontSize;
        if (textFont) tmPro.font = textFont;
        rect.position = referenceCamera.WorldToScreenPoint(target.position);

        Destroy(textObj, duration);

        textObj.transform.SetParent(instance.damageTextCanvas.transform);
        textObj.transform.SetSiblingIndex(0);


        WaitForEndOfFrame w = new WaitForEndOfFrame();
        float t = 0;
        float yOffset = 0;
        while (t < duration)
        {
            tmPro.color = new Color(tmPro.color.r, tmPro.color.g, tmPro.color.b, 1 - t / duration);

            if(target)
            {
                yOffset += speed * Time.deltaTime;
                rect.position = referenceCamera.WorldToScreenPoint(target.position + new Vector3(0,yOffset));
            } else
            {
                // If target is dead, just pan up where the text is at.
                rect.position += new Vector3(0, speed * Time.deltaTime, 0);
            }
            yield return w;
            t += Time.deltaTime;
        }

    }

    public static void GenerateFloatingText(string text, Transform target, float duration = 1f, float speed = 1f)
    {
        if (!instance.damageTextCanvas) return;

        if (!instance.referenceCamera) instance.referenceCamera = Camera.main;

        instance.StartCoroutine(instance.GenerateFloatingTextCoroutine(text, target, duration, speed));
    }

    //define the method to change game state
    public void ChangeState(GameState newState)
    {
        previouseState = currentState;
        currentState = newState;
    }

    public void PauseGame()
    {
        if (currentState != GameState.Paused)
        {
            ChangeState(GameState.Paused);
            Time.timeScale = 0f; //stop the game
            pauseScreen.SetActive(true);
        }
    }

    public void ResumeGame()
    {
        if (currentState == GameState.Paused)
        {
            ChangeState(previouseState);
            Time.timeScale = 1f; //resume game
            pauseScreen.SetActive(false);
        }
    }

    void CheckForPauseAndResume()
    {
        if (Input.GetKeyDown(KeyCode.Escape))
        {
            if (currentState == GameState.Paused)
            {
                ResumeGame();
            }
            else
            {
                PauseGame();
            }
        }
    }

    void DisableScreen()
    {
        pauseScreen.SetActive(false);
        resultsScreen.SetActive(false);
        levelUpScreen.SetActive(false);
    }

    public void GameOver()
    {
        timeSurviveDisplay.text = stopwatchDisplay.text;

        ChangeState(GameState.GameOver);
        Time.timeScale = 0f;
        DisplayResults();
    }

    void DisplayResults()
    {
        resultsScreen.SetActive(true);
    }

    public void AssignChosenCharacterUI(CharacterData chosenCharacterData)
    {
        chosenCharacterImage.sprite = chosenCharacterData.Icon;
        chosenCharacterName.text = chosenCharacterData.name;
    }

    public void AssignLevelReachedUI(int levelReachedData)
    {
        levelReachedDisplay.text = levelReachedData.ToString();
    }

    public void AssignChosenWeaponsAndPassiveItemsUI(List<PlayerInventory.Slot> chosenWeaponsData, List<PlayerInventory.Slot> chosenPassiveItemsData)
    {
        if (chosenWeaponsData.Count != chosenWeaponsUI.Count || chosenPassiveItemsData.Count != chosenPassiveItemsUI.Count)
        {
            Debug.Log("chosen weapon and passive list have different length");
            return;
        }

        //assign chosen weapon data to chosenweaponUI
        for (int i = 0; i < chosenWeaponsUI.Count; i++)
        {
            //check the sprite of the correspoding element in chosenWeaponData is not null
            if (chosenWeaponsData[i].image.sprite)
            {
                //enable the corresponding in chosenWeaponUI and set it sprite to the corresponding sprite in chosenWeaponData
                chosenWeaponsUI[i].enabled = true;
                chosenWeaponsUI[i].sprite = chosenWeaponsData[i].image.sprite;
            }
            else
            {
                //if null disable the correspoding element in chosenWeaponUI
                chosenWeaponsUI[i].enabled = false;
            }
        }

        //assign chosen passive item data to chosenPassiveItemUI
        for (int i = 0; i < chosenPassiveItemsUI.Count; i++)
        {
            //check the sprite of the correspoding element in chosenPassiveItemData is not null
            if (chosenPassiveItemsData[i].image.sprite)
            {
                //enable the corresponding in chosenPassiveItemUI and set it sprite to the corresponding sprite in chosenPassiveItemData
                chosenPassiveItemsUI[i].enabled = true;
                chosenPassiveItemsUI[i].sprite = chosenPassiveItemsData[i].image.sprite;
            }
            else
            {
                //if null disable the correspoding element in chosenPassiveItemUI
                chosenPassiveItemsUI[i].enabled = false;
            }
        }
    }

    void UpdateStopWatch()
    {
        stopwatchTime += Time.deltaTime;

        UpdateStopWatchDisplay();

        if (stopwatchTime >= timeLimit)
        {
            playerObject.SendMessage("Kill");
        }
    }

    void UpdateStopWatchDisplay()
    {
        int minutes = Mathf.FloorToInt(stopwatchTime / 60); //FloortoInt (round up to the nearest int)
        int seconds = Mathf.FloorToInt(stopwatchTime % 60);
        stopwatchDisplay.text = string.Format("{0:00}:{1:00}", minutes, seconds);
    }

    public void StartLevelUp()
    {
        ChangeState(GameState.LeveUp);
        if (levelUpScreen.activeSelf) stackedLevelUps++;
        else
        {
            Time.timeScale = 0f;
            levelUpScreen.SetActive(true);
            playerObject.SendMessage("RemoveAndApplyUpgrades");
        }

    }

    public void EndLevelUp()
    {
        Time.timeScale = 1f;
        levelUpScreen.SetActive(false);
        ChangeState(GameState.Gameplay);

        if (stackedLevelUps > 0)
        {
            stackedLevelUps--;
            StartLevelUp();
        }
    }
}

MissingReferenceException: The object of type ‘UnityEngine.RectTransform’ has been destroyed but you are still trying to access it. Your script should either check if it is null or you should not destroy the object. UnityEngine.Object+MarshalledUnityObject.TryThrowEditorNullExceptionObject (UnityEngine.Object unityObj, System.String parameterName) (at <c01a2e87500f4b88b40eba7308bfcbe6>:0) UnityEngine.Bindings.ThrowHelper.ThrowNullReferenceException (System.Object obj) (at <c01a2e87500f4b88b40eba7308bfcbe6>:0) UnityEngine.Transform.set_position (UnityEngine.Vector3 value) (at <c01a2e87500f4b88b40eba7308bfcbe6>:0) GameManager+<GenerateFloatingTextCoroutine>d__35.MoveNext () (at Assets/Scripts/GameManager.cs:139) UnityEngine.SetupCoroutine.InvokeMoveNext (System.Collections.IEnumerator enumerator, System.IntPtr returnValueAddress) (at <c01a2e87500f4b88b40eba7308bfcbe6>:0) UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr, Boolean&)

[Alp Apustaja]

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In the GenerateFloatingTextCoroutine method, add a null check for rect before attempting to modify its position:

while (t < duration)
{
    tmPro.color = new Color(tmPro.color.r, tmPro.color.g, tmPro.color.b, 1 - t / duration);

    if(target)
    {
        yOffset += speed * Time.deltaTime;
        if (rect != null) // Add this null check
        {
            rect.position = referenceCamera.WorldToScreenPoint(target.position + new Vector3(0,yOffset));
        }
    } 
    else
    {
        // If target is dead, just pan up where the text is at.
        if (rect != null) // Add this null check
        {
            rect.position += new Vector3(0, speed * Time.deltaTime, 0);
        }
    }
    yield return w;
    t += Time.deltaTime;
}

This modification will prevent the MissingReferenceException by checking if rect is not null before attempting to modify its position.

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