C#中缺少什么引用异常? [英] What is missing reference exception in c#?

问题描述

我正在用统一3d制作游戏，但缺少参考异常.错误 不会出现在我的脚本编辑器中，所以我不知道此错误与什么有关. 这是Gamemanager脚本:

I am making a game in unity 3d and I have missing reference exception.The error don't appear in my script editor so I don't know what is this error related to. Here is the Gamemanager script:

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

public class Gamemanager : MonoBehaviour
{
public List<Character> Characters = new List<Character>();
public List <Item> AllItems = new List<Item> ();
bool ShowCharWheel;
public int SelectedCharacter;
int LastCharacter;
public static Gamemanager Instance;
public bool CanShowSwitch = true;
public Character CurrentCharacter; 

void Awake()
{
    foreach (Character c in Characters)
    {
        c.Instance = Instantiate(c.PlayerPrefab, c.HomeSpawn.position, c.HomeSpawn.rotation) as GameObject;
        c.Instance.GetComponent<PlayerController> ().LocalCharacter = c;
    }
    ChangeCharacterStart(Characters[PlayerPrefs.GetInt("SelectedChar")]);
}
// Use this for initialization
void Start()
{

}
void ChangeCharacterStart(Character c)
{

    LastCharacter = SelectedCharacter;
    SelectedCharacter = Characters.IndexOf(c);
    CurrentCharacter = c;
    Characters [LastCharacter].Instance.GetComponent<PlayerController> ().CanPlay = false;
    Characters[SelectedCharacter].Instance.GetComponent<PlayerController>().CanPlay = true;
    Camera.main.GetComponent<SmoothFollow>().target = Characters[SelectedCharacter].Instance.transform;
    PlayerPrefs.SetInt("SelectedChar", SelectedCharacter);
}
// Update is called once per frame
void Update()
{
    if (CanShowSwitch) {
        if (Input.GetKey (KeyCode.C)) {
            ShowCharWheel = true;

        } else if (Input.GetKey (KeyCode.V)) {
            ShowCharWheel = false;

        }

    }
}

void ChangeCharacter(Character c)
{
    c.Instance.GetComponent<AI> ().DoneHome = false;
    if (Vector3.Distance (Characters [SelectedCharacter].Instance.transform.position, c.Instance.transform.position) > 10) {
        sequencemanager.Instance.StartCoroutine ("DoCharSwitch", c);
        CanShowSwitch = false;
        LastCharacter = SelectedCharacter;
        SelectedCharacter = Characters.IndexOf (c);
        CurrentCharacter = c;
        Characters [LastCharacter].Instance.GetComponent<PlayerController> ().CanPlay = false;
        Characters [SelectedCharacter].Instance.GetComponent<PlayerController> ().CanPlay = true;
        PlayerPrefs.SetInt ("SelectedChar", SelectedCharacter);

    } else {
        LastCharacter = SelectedCharacter;
        SelectedCharacter = Characters.IndexOf(c);
        CurrentCharacter = c;
        Characters [LastCharacter].Instance.GetComponent<PlayerController> ().CanPlay = false;
        Characters [SelectedCharacter].Instance.GetComponent<PlayerController> ().CanPlay = true;
        PlayerPrefs.SetInt ("SelectedChar", SelectedCharacter);
        Camera.main.GetComponent<SmoothFollow> ().target = Characters [SelectedCharacter].Instance.transform;

    }


}


void OnGUI()
{
    if (ShowCharWheel)
    {
        GUILayout.BeginArea(new Rect(Screen.width - 64, Screen.height - 256, 64, 208), GUIContent.none, "box");
        foreach (Character c in Characters)
        {
            if (GUILayout.Button(c.Icon, GUILayout.Width(64), GUILayout.Height(64)))
            {
                ChangeCharacterStart(c);
            }
        }
    GUILayout.EndArea();
    }
}
    }

  [System.Serializable]
  public class Character
  {
public string Name;
public Texture2D Icon;
public GameObject PlayerPrefab;
public GameObject Instance;
public Transform HomeSpawn;
   }

[System.Serializable]
 public class Item
{
public string Name;
public Texture2D Icon;
public ItemInstance InstancePrefab;
 }

错误在线

c.Instance = Instantiate(c.PlayerPrefab, c.HomeSpawn.position, c.HomeSpawn.rotation) as GameObject;

这是我的编辑器图像，带有错误.主要问题是，当我启动游戏时，它破坏了游戏管理器脚本. 还有一件重要的事情:我迁移了这个项目.我不得不重新安装Windows.

This is my editor image with error.The main problem is when I start the game it destroy the gamemanager script. And another important thing.I migrated this project.I had to reinstall windows.Before that the error didn't appeared.And now it do.And I am sure I took the whole pro

推荐答案

我只是一个初级开发人员，没有太多经验，但是您的代码看起来很凌乱.可能存在更多的null refs错误，因此很可能您没有分配/保存预制件或要使用的对象被破坏.检查[如何使用monobehaviour进行调试]( https://unity3d.com/learn/tutorials/topics/scripting/monodevelops-debugger ).因此，请设置一些断点，然后逐一进行.激活断点后，您可以将鼠标悬停在变量上，并检查其是否具有某些值.我强烈建议您像这样在单独的行中进行任何分配:

I just a junior developer without much of experience but your code looks messy. May be there is more null refs errors so most probably you did not assign/ save to prefab something or an object that you want to use is destroyed. Check [how to debug with monobehaviour] (https://unity3d.com/learn/tutorials/topics/scripting/monodevelops-debugger). So put some break point, and go through them one by one. When break point activated you can hover over variable and check if it has some value. I strongly suggest you make any assignment on separate line like this:

c.Instance = Instantiate(c.PlayerPrefab, c.HomeSpawn.position, c.HomeSpawn.rotation) as GameObject;

应该是这样的:

GameObject newGameObject = Instantiate(c.PlayerPrefab, c.HomeSpawn.position, c.HomeSpawn.rotation) as GameObject;
c.Instance = newGameObject;

在这种情况下，您可以检查是否确实有newGameObject等.

In that case you can check if you really have newGameObject and so on.

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