c# - Camera.main 空引用异常

Question

我是 C# 和 Unity 的新手，我已经阅读了整个论坛，但我仍然被困住了。这是我收到的错误:

NullReferenceException: Object reference not set to an instance of an object ClickToMove.Update () (at Assets/Scripts/ClickToMove.cs:27)

这就是我所拥有的...

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

 public class ClickToMove : MonoBehaviour {
     [Header("Stats")]
     public float attackDistance;
     public float attackRate;
     private float nextAttack;

     private NavMeshAgent navMeshAgent;
     private Animator anim;

     private Transform targetedEnemy;
     private bool enemyClicked;
     private bool walking;    
     void Awake ()
     {
         anim = GetComponent<Animator>();
         navMeshAgent = GetComponent<NavMeshAgent>();
     }

     // Update is called once per frame
     void Update ()
     {
         Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
         RaycastHit hit;

         if (Input.GetButtonDown("Fire2"))
         {
             if (Physics.Raycast(ray, out hit, 1000))
             {
                 if (hit.collider.tag == "Enemy")
                 {
                     targetedEnemy = hit.transform;
                     enemyClicked = true;
                     //print("Enemy Hit");
                 }
                 else
                 {
                     walking = true;
                     enemyClicked = false;
                     navMeshAgent.isStopped = false;
                     navMeshAgent.destination = hit.point;
                 }
             }
         }
         if (enemyClicked)
         {
             MoveAndAttack();
         }

         if (navMeshAgent.remainingDistance <= navMeshAgent.stoppingDistance)
         {
             walking = false;
         }
         else
         {
             walking = true;
         }

         //anim.SetBool("isWalking", walking);
     }

     void MoveAndAttack()
     {
         if(targetedEnemy == null)
         {
             return;
         }

         navMeshAgent.destination = targetedEnemy.position;

         if(navMeshAgent.remainingDistance > attackDistance)
         {
             navMeshAgent.isStopped = false;
             walking = true;
         }
         else
         {
             transform.LookAt(targetedEnemy);
             Vector3 dirToAttack = targetedEnemy.transform.position - transform.position;

             if(Time.time > nextAttack)
             {
                 nextAttack = Time.time + attackRate;
             }
             navMeshAgent.isStopped = true;
             walking = false;
         }
     }
 }

第 27 行以“Ray ray = Camera.main.ScreenPointToRay...”开头

Answer 1

为了调用 Camera.main.ScreenPointToRay()，您需要在场景中使用带有 MainCamera 标签的相机。没有这个，Camera.main 不存在，导致空引用异常。