Bug Helping , I spend three hours but useless

NullReferenceException: Object reference not set to an instance of an object
EnemyControl.OnEnable () (at Assets/Scripts/Characters/EnemyControl.cs:72)

Thank very much

Code (CSharp):

1.  
2. [code=CSharp]public class Signleton<T> : MonoBehaviour where T : Signleton<T>
3. {
4.     private static T instance;
5.  
6.     public static T Instance
7.     {
8.         get { return instance; }
9.         set { instance = value; }
10.     }
11.  
12.     //只允许继承类访问的函数变量与方法
13.     //纯虚函数
14.     protected virtual void Awake()
15.     {
16.         if(instance != null) Destroy(gameObject);
17.         else instance = (T)this;
18.     }
19.  
20.     public static bool IsInitialized
21.     {
22.         get { return instance != null; }
23.     }
24.  
25.     protected virtual void OnDestroy()
26.     {
27.         if(instance == this)
28.         {
29.             instance = null;
30.         }
31.     }
32.  
33. }

public class EnemyControl : MonoBehaviour , IEndGameObserver
{
private NavMeshAgent agent;
private EnemyStates enemystates;
private Animator Anim;
private Collider Coll;

[Header("Basic Setting")]
public float sighRadius;
private GameObject attacktarget;
public bool isGuard;
private float speed;
public float LookAtTime;
private float remainLookAtTime;
private CharacterStats characterStats;
private float lastAttackTime;
private Vector3 guardPos;
private Quaternion guardRotation;
//配合动画
bool isWalk;
bool isChase;
bool isFollow;
bool Critical;
bool isDeath;
bool PlayerDead;

[Header("Patrol State")]
public float patroRange;
private Vector3 wayPoint;
private Vector3 targetPoint;

private void Awake()
{
agent = GetComponent<NavMeshAgent>();
Anim = GetComponent<Animator>();
Coll = GetComponent<Collider>();
speed = agent.speed;
targetPoint = transform.position;
remainLookAtTime = LookAtTime;
guardPos = transform.position;
guardRotation = transform.rotation;
characterStats = GetComponent<CharacterStats>();
}

private void Start()
{
if(isGuard)
{
enemystates = EnemyStates.GUARD;
}
else
{
enemystates = EnemyStates.PATROL;
GetNewWayPoint();
}
}

private void OnEnable()
{
GameManager.Instance.AddObserver(this);
}

private void Update()
{
isDeath = characterStats.CurrentHealth == 0;
if(!PlayerDead)
{
SwitchStates();
SwitchAnim();
lastAttackTime -= Time.deltaTime;
}
}

private void SwitchAnim()
{
Anim.SetBool("walk", isWalk);
Anim.SetBool("chase", isChase);
Anim.SetBool("follow", isFollow);
Anim.SetBool("Critical", characterStats.isCritical);
Anim.SetBool("Death", isDeath);
}

private void SwitchStates()
{
//如果死了 ， 切换死亡状态
if(isDeath)
{
enemystates = EnemyStates.DEAD;
}
else if(FoundPlayer())
{
//如果发现Player ，切换CHASE
enemystates = EnemyStates.CHASE;
}

switch (enemystates)
{
case EnemyStates.GUARD:
isChase = false;
if(transform.position != guardPos)
{
isWalk = true;
agent.isStopped = false;
agent.destination = guardPos;
if(Vector3.SqrMagnitude(transform.position - guardPos) <= agent.stoppingDistance)
{
isWalk = false;
transform.rotation = Quaternion.Lerp(transform.rotation, guardRotation, 0.01f);
}
}
break;
case EnemyStates.PATROL:
isChase = false;
agent.speed = speed * 0.5f;
//判断是否走到了某个点
if(Vector3.Distance(wayPoint , transform.position) <= agent.stoppingDistance)
{
isWalk = false;
if(remainLookAtTime > 0) remainLookAtTime -= Time.deltaTime;
else GetNewWayPoint();
}
else
{
isWalk = true;
agent.destination = wayPoint;
}
break;
case EnemyStates.CHASE:
//追击Player
//Player脱离，回归原状态
isWalk = false;
isChase = true;
agent.speed = speed;
//没找到
if(!FoundPlayer())
{
isFollow = false;
if (remainLookAtTime > 0)
{
agent.destination = transform.position;
remainLookAtTime -= Time.deltaTime;
}
else
{
if (isGuard) enemystates = EnemyStates.GUARD;
else enemystates = EnemyStates.PATROL;
}
}
else
{
//找到了
//启动追击
isFollow = true;
agent.isStopped = false;
agent.destination = attacktarget.transform.position;

//在攻击范围内则重拳出击
if(TargetInAttackRange() || TargetInSkillRange())
{
isFollow = false;
agent.isStopped = true;

if(lastAttackTime < 0)
{
lastAttackTime = characterStats.attackData.CoolDown;
//暴击判断
//随机数值是否小于暴击率，如果是 则暴击
characterStats.isCritical = Random.value < characterStats.attackData.CriticalChance;
//执行攻击
Attack();
}
}
}
break;
case EnemyStates.DEAD:
Coll.enabled = false;
agent.enabled = false;
Destroy(gameObject, 2);
break;
}
}

//攻击方法
private void Attack()
{
transform.LookAt(attacktarget.transform);
if(TargetInAttackRange())
{
//普通攻击动画
Anim.SetTrigger("Attack");
}
if(TargetInSkillRange())
{
//技能攻击动画
Anim.SetTrigger("Skill");
}
}

//判断Enemy是否找到了Plyaer
bool FoundPlayer()
{
var colliders = Physics.OverlapSphere(transform.position, sighRadius);
foreach(var target in colliders)
{
if (target.CompareTag("Player"))
{
attacktarget = target.gameObject;
return true;
}
}
attacktarget = null;
return false;
}

private void GetNewWayPoint()
{
remainLookAtTime = LookAtTime;
float randomX = Random.Range(-patroRange, patroRange);
float randomZ = Random.Range(-patroRange, patroRange);
Vector3 randomPoint = new Vector3(randomX + targetPoint.x, transform.position.y , targetPoint.z + randomZ);
NavMeshHit hit;
wayPoint = NavMesh.SamplePosition(randomPoint, out hit , patroRange , 1) ? hit.position : this.transform.position;
}

private bool TargetInAttackRange()
{
if (attacktarget != null)
{
return Vector3.Distance(attacktarget.transform.position, this.transform.position) <= characterStats.attackData.AttackRange;
}
return false;
}

private bool TargetInSkillRange()
{
if (attacktarget != null)
return Vector3.Distance(attacktarget.transform.position, this.transform.position) <= characterStats.attackData.SkillRange;
return false;
}

private void OnDrawGizmosSelected()
{
Gizmos.color = Color.blue;
Gizmos.DrawWireSphere(transform.position, sighRadius);
}

//Animation Event
private void Hit()
{
if(attacktarget != null)
{
var targetStats = attacktarget.GetComponent<CharacterStats>();
targetStats.TakeDamage(characterStats, targetStats);
}
}

//获取 Player 消失的广播
public void EndNotify()
{
//获取动画
//停止所有移动
//停止Agent
Debug.Log("Player已死");
Anim.SetBool("Win", true);
PlayerDead = true;
isChase = false;
isWalk = false;
attacktarget = null;
}
}[/code]

Code (CSharp):

1. public class GameManager : Signleton<GameManager>
2. {
3.     public CharacterStats playerStats;
4.  
5.     List<IEndGameObserver> endGameObservers = new List<IEndGameObserver>();
6.  
7.     protected override void Awake()
8.     {
9.         base.Awake();
10.     }
11.  
12.     public void RigisterPlayer(CharacterStats player)
13.     {
14.         playerStats = player;
15.     }
16.  
17.     public void AddObserver(IEndGameObserver observer)
18.     {
19.         endGameObservers.Add(observer);
20.         Debug.Log(endGameObservers.Count);
21.     }
22.  
23.     public void RemoveObserver(IEndGameObserver observer)
24.     {
25.         endGameObservers.Remove(observer);
26.     }
27.  
28.     public void NotifyObserver()
29.     {
30.         foreach (var observer in endGameObservers)
31.         {
32.             observer.EndNotify();
33.         }
34.     }
35. }