NullReferenceException in Ruby's Adventure: 2D Beginner

I try to finish the "Ruby's Adventure: 2D Beginner", and when I want to finish "Sprite Animation", there are some errors. I just copy the code from the tutorial and I tried many times but totally don't know how to fix it.
The error is:
NullReferenceException: Object reference not set to an instance of an object
Rubycontroller.Update () (at Assets/Script/Rubycontroller.cs:48)

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4.  
5. public class Rubycontroller : MonoBehaviour
6. {
7.     public float speed = 3.0f;
8.  
9.     public int maxHealth = 5;
10.     public float timeInvincible = 2.0f;
11.  
12.     public int health { get { return currentHealth; } }
13.     int currentHealth;
14.  
15.     bool isInvincible;
16.     float invincibleTimer;
17.  
18.     Rigidbody2D rigidbody2d;
19.     Animator animator;
20.     Vector2 lookDirection = new Vector2(0, -1);
21.  
22.     // Start is called before the first frame update
23.     void Start()
24.     {
25.         rigidbody2d = GetComponent<Rigidbody2D>();
26.  
27.         currentHealth = 4;
28.     }
29.  
30.     // Update is called once per frame
31.     void Update()
32.     {
33.         float horizontal = Input.GetAxis("Horizontal");
34.         float vertical = Input.GetAxis("Vertical");
35.  
36.         //Vector2 position = rigidbody2d.position;
37.         //position.x = position.x + speed * horizontal * Time.deltaTime;
38.         //position.y = position.y + speed * vertical * Time.deltaTime;
39.  
40.         Vector2 move = new Vector2(horizontal, vertical);
41.  
42.         if (!Mathf.Approximately(move.x, 0.0f) || !Mathf.Approximately(move.y, 0.0f))
43.         {
44.             lookDirection.Set(horizontal, vertical);
45.             lookDirection.Normalize();
46.         }
47.  
48.         animator.SetFloat("Speed", move.magnitude);
49.         animator.SetFloat("Look X", lookDirection.x);
50.         animator.SetFloat("Look Y", lookDirection.y);
51.        
52.  
53.         Vector2 position = rigidbody2d.position;
54.  
55.         position = position + move * speed * Time.deltaTime;
56.  
57.         rigidbody2d.MovePosition(position);
58.  
59.         if (isInvincible)
60.         {
61.             invincibleTimer -= Time.deltaTime;
62.             if (invincibleTimer < 0)
63.                 isInvincible = false;
64.         }
65.  
66.     }
67.  
68.     public void ChangeHealth(int amount)
69.     {
70.         if (amount < 0)
71.         {
72.             animator.SetTrigger("Hit");
73.  
74.             if (isInvincible)
75.                 return;
76.  
77.             isInvincible = true;
78.             invincibleTimer = timeInvincible;
79.         }
80.  
81.         currentHealth = Mathf.Clamp(currentHealth + amount, 0, maxHealth);
82.         Debug.Log(currentHealth + "/" + maxHealth);
83.     }
84. }
85.  

Appreciate any help!!

 

I can't see anywhere where do you get a reference to the animator.
You have this line at the top :

Code (csharp):

1.  
2. Animator animator;
3.  

But you never make a reference to it.
You can do it in two ways. Depending if the script is attached to a GameObject that have Animator or not.

You can change the animator declaration to :

Code (csharp):

1.  
2. public Animator animator;
3.  

And then in the editor in the inspector to assign the Animator component.
Or leave it as it is and add in the Start the line :

Code (csharp):

1.  
2. animator = GetComponent<Animator>();
3.  

 

Got it, and it works, thank you very very much!

 

Thank you!