Null reference Error in UNET

Question

Using this script i can shoot the projectiles from Server to Client. But when i try to shoot the projectiles in the client it shows null reference error. Can someone help me?

This is the error :

NullReferenceException: Object reference not set to an instance of an object NetworkPlayerManager.CmdFire () (at Assets/Networked Scripts/NetworkPlayerManager.cs:83) NetworkPlayerManager.InvokeCmdCmdFire

The script is given below:

 public class NetworkPlayerManager : NetworkBehaviour {
 
 #region Variables
 
 public GameObject Ball;
 public float Power = 10f;
 public PlayerController activePlayer;
 public PlayerController player1,player2,player3;
 public Renderer player1color,player2color,player3color;
 public Transform PlayerFormation;
 public Button b1,b2,b3;
 public Canvas myCanvas;
 public Camera myCamera;
 
 private int playerNumber;
 private Transform obj;
 private string targetTag="Target";
     
 #endregion
 
 #region Built-in Functions
 
     void Start ()
     {    
         if (!isLocalPlayer)
         {
             AssignTags();    
             transform.name="Opponent Player- Not Local Player";                    
             return;
         }    
 
     }
 
     void Update () 
     {
         if (!isLocalPlayer)        
             return;    
 
         if (Input.GetMouseButtonDown(0))
         {
             Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
             RaycastHit hit = new RaycastHit();                  
             if (Physics.Raycast(ray, out hit))
             {
                 if (hit.transform.tag==targetTag&&!hit.transform.GetComponent<PlayerController>().is_hit)
                 {
                     obj=hit.transform;
                     CmdFire();                    
                     PlayerSelector();    
                 }                
             }        
         }
     }
     
 #endregion
 
 #region Override
 
     public override void OnStartLocalPlayer()
     {
         ActivateEssentials();        
         ChangeColor();    
         AssignButtons();
         TurnDecider();    
 
         if (isServer)
             SetName("Host Player - Local Player");                    
         else        
             SetName("Client Player - Local Player");        
     }
 
 #endregion
 
 #region Commands
     
     [Command]
     public void CmdFire()
     {
         GameObject ball = Instantiate(Ball,activePlayer.shooter.position,Quaternion.identity) as GameObject;
         ball.GetComponent<Rigidbody>().velocity = (obj.position - activePlayer.shooter.position).normalized * Power;
         NetworkServer.Spawn(ball);    
     }
 
 #endregion
 
 #region Client Rpc    
 
     [ClientRpc]
     public void RpcFire()
     {        
         if (!isServer)
         {
             print("Called RPC Fire()");                
         }            
     }
 
 #endregion    
 
 #region Other Functions    
 
     public void SetName(string name)
     {
         transform.name=name;
     }
 
     public void AssignTags()
     {
         transform.tag=targetTag;
         player1.tag=targetTag;
         player2.tag=targetTag;
         player3.tag=targetTag;
     }
 
     public void AssignButtons()
     {
         b1.onClick.AddListener(player1.Jump);
         b2.onClick.AddListener(player2.Jump);
         b3.onClick.AddListener(player3.Jump);
     }
 
     public void ActivateEssentials()
     {
         playerNumber = 1;        
         myCamera.gameObject.SetActive(true);
         myCanvas.gameObject.SetActive(true);
     }
 
     public void ChangeColor()
     {
         player1color.material.color = Color.green;
         player2color.material.color = Color.green;
         player3color.material.color = Color.green;        
     }
 
     public void PlayerSelector()
     {
         if (playerNumber == 3)        
             playerNumber = 1;       
         else       
             playerNumber++;
         
         TurnDecider();
     }
 
     public void TurnDecider()
     {
         switch (playerNumber)
         {
             case 1:
                     player1.isReady=false;                      
                     player2.isReady = true;
                     player3.isReady = false;
                     activePlayer=player2;                
                     break;
 
             case 2:
                        player1.isReady=false;                      
                     player2.isReady = false;
                     player3.isReady = true;
                     activePlayer=player3;                      
                        break;
 
             case 3:
                        player1.isReady=true;                      
                     player2.isReady = false;
                     player3.isReady = false;
                     activePlayer=player1;                   
                       break;
         }
     }         
 #endregion        
 }

Answer 1

If you understand the error message, it should be easy to track down where and what is going wrong.

"NullReferenceException: Object reference not set to an instance of an object" This means you are using a variable that is currently set to null. For example, maybe you forgot to "new" something, or forgot to assign a variable via the properties window.

"NetworkPlayerManager.CmdFire () (at Assets/Networked Scripts/NetworkPlayerManager.cs:83) " This is saying the problem happened on line 83 of NetworkPlayerManager.cs, (and its telling you the function you are in is called NetworkPlayerManager.CmdFire ()).

It is a bit hard to tell exactly which is line 83 from the way you have pasted your code, but here is the relevant function:

   public void CmdFire()
  {
      GameObject ball = Instantiate(Ball,activePlayer.shooter.position,Quaternion.identity) as GameObject;
      ball.GetComponent<Rigidbody>().velocity = (obj.position - activePlayer.shooter.position).normalized * Power;
      NetworkServer.Spawn(ball);    
  }

Ball is a variable that should be set via the properties on this game object in Unity. Did you set it?

Or maybe activePlayer is null?

You can either set a break point in this function and use the debugger to figure out which one is wrong, or write a series of Debug.Log statements to print out if the variables are null or not.

Null reference Error in UNET

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