统一为什么会出现错误 NullReferenceException：对象引用未设置为 CameraScript 上的对象实例？

Question

一旦我从层次结构中删除 AIThirdPersonController，错误就开始了。 现在我有了主摄像头和 ThirdPersonController。

我在 Inspector 中有 Main Camera 我添加了一个 Camera Script.cs

using UnityEngine;
using System.Collections;

public class CameraScript : MonoBehaviour {


    public Transform TargetLookAt;

    public float Distance = 5.0f;
    public float DistanceMin = 3.0f;
    public float DistanceMax = 10.0f;

    private float mouseX = 0.0f;
    private float mouseY = 0.0f;
    private float startingDistance = 0.0f;    
    private float desiredDistance = 0.0f;

    public float X_MouseSensitivity = 5.0f;
    public float Y_MouseSensitivity = 5.0f;
    public float MouseWheelSensitivity = 5.0f;
    public float Y_MinLimit = -40.0f;
    public float Y_MaxLimit = 80.0f;

    public float DistanceSmooth = 0.05f;    
    private float velocityDistance = 0.0f;    
    private Vector3 desiredPosition = Vector3.zero;

    public float X_Smooth = 0.05f;
    public float Y_Smooth = 0.1f;
    private float velX = 0.0f;
    private float velY = 0.0f;
    private float velZ = 0.0f;
    private Vector3 position = Vector3.zero;

    CursorLockMode wantedMode;    


    void  Start (){
        Distance = Mathf.Clamp(Distance, DistanceMin, DistanceMax);
        startingDistance = Distance;
        Reset();
        SetCursorState();
        OnGUI();

    }

    void Update(){
    }

    void  FixedUpdate (){
        if (TargetLookAt == null)
            return;

        HandlePlayerInput();

        CalculateDesiredPosition();

        UpdatePosition();
    }

    void  HandlePlayerInput (){
        float deadZone= 0.01f; // mousewheel deadZone

        //if (Input.GetMouseButton(1))
        //{
        mouseX += Input.GetAxis("Mouse X") * X_MouseSensitivity;
        mouseY -= Input.GetAxis("Mouse Y") * Y_MouseSensitivity;
        //}

        // this is where the mouseY is limited - Helper script
        mouseY = ClampAngle(mouseY, Y_MinLimit, Y_MaxLimit);

        // get Mouse Wheel Input
        if (Input.GetAxis("Mouse ScrollWheel") < -deadZone || Input.GetAxis("Mouse ScrollWheel") > deadZone)
        {
            desiredDistance = Mathf.Clamp(Distance - (Input.GetAxis("Mouse ScrollWheel") * MouseWheelSensitivity), 
                DistanceMin, DistanceMax);
        }
    }

    void  CalculateDesiredPosition (){
        // Evaluate distance
        Distance = Mathf.SmoothDamp(Distance, desiredDistance, ref velocityDistance, DistanceSmooth);

        // Calculate desired position -> Note : mouse inputs reversed to align to WorldSpace Axis
        desiredPosition = CalculatePosition(mouseY, mouseX, Distance);
    }

    Vector3  CalculatePosition ( float rotationX ,   float rotationY ,   float distance  ){
        Vector3 direction = new Vector3(0, 0, -distance);
        Quaternion rotation = Quaternion.Euler(rotationX, rotationY, 0);
        return TargetLookAt.position + (rotation * direction);
    }

    void  UpdatePosition (){
        float posX= Mathf.SmoothDamp(position.x, desiredPosition.x, ref velX, X_Smooth);
        float posY= Mathf.SmoothDamp(position.y, desiredPosition.y, ref velY, Y_Smooth);
        float posZ= Mathf.SmoothDamp(position.z, desiredPosition.z, ref velZ, X_Smooth);
        position = new Vector3(posX, posY, posZ);

        transform.position = position;

        transform.LookAt(TargetLookAt);
    }

    void  Reset (){
        mouseX = 0;
        mouseY = 10;
        Distance = startingDistance;
        desiredDistance = Distance;
    }

    float ClampAngle ( float angle ,   float min ,   float max  ){
        while (angle < -360 || angle > 360)
        {
            if (angle < -360)
                angle += 360;
            if (angle > 360)
                angle -= 360;
        }

        return Mathf.Clamp(angle, min, max);
    }

    // Apply requested cursor state
    void SetCursorState ()
    {
        Cursor.lockState = wantedMode;
        // Hide cursor when locking
        Cursor.visible = (CursorLockMode.Locked != wantedMode);
    }

    void OnGUI ()
    {
        GUILayout.BeginVertical ();
        // Release cursor on escape keypress
        if (Input.GetKeyDown (KeyCode.Escape))
            Cursor.lockState = wantedMode = CursorLockMode.None;

        switch (Cursor.lockState) {
        case CursorLockMode.None:
            GUILayout.Label ("Cursor is normal");
            if (GUILayout.Button ("Lock cursor"))
                wantedMode = CursorLockMode.Locked;
            if (GUILayout.Button ("Confine cursor"))
                wantedMode = CursorLockMode.Confined;
            break;
        case CursorLockMode.Confined:
            GUILayout.Label ("Cursor is confined");
            if (GUILayout.Button ("Lock cursor"))
                wantedMode = CursorLockMode.Locked;
            if (GUILayout.Button ("Release cursor"))
                wantedMode = CursorLockMode.None;
            break;
        case CursorLockMode.Locked:
            GUILayout.Label ("Cursor is locked");
            if (GUILayout.Button ("Unlock cursor"))
                wantedMode = CursorLockMode.None;
            if (GUILayout.Button ("Confine cursor"))
                wantedMode = CursorLockMode.Confined;
            break;
        }

        GUILayout.EndVertical ();

        SetCursorState ();
    }
}

错误就行了：

GUILayout.BeginVertical ();

我得到的错误是：

NullReferenceException: Object reference not set to an instance of an object
UnityEngine.GUILayoutUtility.BeginLayoutGroup (UnityEngine.GUIStyle style, UnityEngine.GUILayoutOption[] options, System.Type layoutType) (at C:/buildslave/unity/build/Runtime/IMGUI/Managed/GUILayoutUtility.cs:252)
UnityEngine.GUILayout.BeginVertical (UnityEngine.GUIContent content, UnityEngine.GUIStyle style, UnityEngine.GUILayoutOption[] options) (at C:/buildslave/unity/build/Runtime/IMGUI/Managed/GUILayout.cs:308)
UnityEngine.GUILayout.BeginVertical (UnityEngine.GUILayoutOption[] options) (at C:/buildslave/unity/build/Runtime/IMGUI/Managed/GUILayout.cs:296)
CameraScript.OnGUI () (at Assets/My Scripts/CameraScript.cs:135)
CameraScript.Start () (at Assets/My Scripts/CameraScript.cs:43)

在 Camera Script 区域的 Main Camera Inspector 中，Target look At 设置为 ThirdPersonController。

Answer 1

您收到此错误是因为您正在从 Start() 函数调用 OnGUI() 函数。不要那样做。

void Start()
{
    Distance = Mathf.Clamp(Distance, DistanceMin, DistanceMax);
    startingDistance = Distance;
    Reset();
    SetCursorState();
    OnGUI();///--------------------->DON'T DO THIS!
}

OnGUI() 函数是 Unity GUI 回调函数，由 Unity 自动调用以创建 GUI。从您的 Start() 函数中删除该行代码，您的问题应该就消失了。如果您有任何要从 Start() 函数启动的内容，请创建一个新函数来执行此操作。

该新函数不应命名为 OnGUI()，并且不得包含任何 GUI 函数，例如 GUILayout.BeginVertical();GUILayout.EndVertical();、GUILayout.Button("Confine cursor")。

通知：

OnGUI() 函数不应在您的游戏中使用。您应该仅在编辑器中仅将其用作测试游戏功能的测试工具。在实际游戏中使用时非常昂贵且速度慢。您可以了解应该使用的新 Unity UI here。

Answer 2

当您的堆栈跟踪显示您拥有源代码时，请在调试器中逐步检查它以找出什么是 null。很可能是您没有正确配置 GUILayout。

Apparently，OnGUI 和 GUILayout 无论如何都是“遗留”代码，因此无论新的替代方案是什么，都值得研究。