Roll a Ball NullReferenceException

Questions & Answers
1

So i found another question relating to this on the boards but found no answer so I’m asking in regards to my specific error. The game actually still works perfectly fine but I’m getting an error at the bottom of the screen that reads NullReferenceException: Object reference not set to an instance of an object. Both errors point to my PlayerController script. The first says “PlayerController.SetCountText () (at Assets/Scripts/PlayerController.cs:44)”. The second reads “PlayerController.OnTriggerEnter (UnityEngine>Collider other) (at Assets/scripts/PlayerController.cs:38)” I’m assuming those lines are telling me where in my code I’m having problems but wtf I can’t figure it out. As far as I can tell my code is exactly the same as in the Roll A Ball tutorials. Here’s my Player Controller code:

1 using UnityEngine;
2 using UnityEngine.UI;
3 using System.Collections;
4
5  public class PlayerController : MonoBehaviour {
6
7   public float speed;
8   public Text countText;
9    public Text winText;
10
11	private Rigidbody rb;
12    private int count;
13
14	void Start ()
15	{
16		rb = GetComponent<Rigidbody> ();
17       count = 0;
18       SetCountText ();
19        winText.text = "";
20	}
21
22	void FixedUpdate () 
23	{
24		float moveHorizontal = Input.GetAxis ("Horizontal");
25		float moveVertical = Input.GetAxis ("Vertical");
26
27		Vector3 movement = new Vector3 (moveHorizontal, 0.0f, moveVertical);
28
29		rb.AddForce (movement * speed);
30	}
31
32    void OnTriggerEnter(Collider other)
33    {
34        if (other.gameObject.CompareTag("Pick Up"))
35       {
36            other.gameObject.SetActive(false);
37            count = count + 1;
38            SetCountText();
39        }
40    }
41
42    void SetCountText ()
43    {
44        countText.text = "Count: " + count.ToString ();
45        if (count >= 9)
46        {
47            winText.text = "You Win!";
48        }
49    }
50 }
51

Thanks in advance for any help!

2

if you didn’t set countText in the inspector, it would be trying to access a null object (which doesn’t have a variable text). You can fix this by changing line 44 to this:

if (countText != null)
    countText.text = "Count: " + count.ToString();
else
    Debug.LogWarning("Count Text is null!");

You may want to do the same with winText on lines 19 and 47, and even rb in case the GameObject happens to not have an attached Rigidbody.

Edit

As talked about in the tutorial, you must provide references to all the components and objects you want to access in your scripts. If any of these references are null, it will throw an error when you try to change their variables.

In the Roll-a-Ball tutorial, the UI Texts and Player GameObjects should look something like the image below. The Player GameObject should have a Rigidbody component, and the PlayerController script’s Count Text and Win Text variables should reference the Text GameObjects in the scene hierarchy, by dragging the Text GameObjects from the hierarchy onto the script’s variable fields.

83858-capture2.png