UIFade not working

Hi Im new to unity, I am trying to make a fade between scenes. It fades to black when I exit a scene, when I put the code "UIFade.instance" in AreaExit.cs. So that works but I get a error when putting the same code "UIFade.instance" into AreaEntrance.cs.
So for some reason it recognises the code in AreaExit.cs but not in AreaEntrance.cs

This is basic error I got:
NullReferenceException: Object reference not set to an instance of an object
AreaEntrance.Start () (at Assets/Scripts/AreaEntrance.cs:18)

Here is my code:

AreaExit:

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4. using UnityEngine.SceneManagement;
5.  
6. public class AreaExit : MonoBehaviour
7. {
8.  
9.     public string areaToLoad;
10.  
11.     public string areaTransitionName;
12.  
13.     public AreaEntrance theEntrance;
14.  
15.     public float waitToLoad = 1f;
16.     private bool shouldLoadAfterFade;
17.  
18.     // Start is called before the first frame update
19.     void Start()
20.     {
21.          theEntrance.transitionName = areaTransitionName;
22.     }
23.  
24.     // Update is called once per frame
25.     void Update()
26.     {
27.         if(shouldLoadAfterFade)
28.         {
29.            waitToLoad -= Time.deltaTime;
30.            if(waitToLoad <- 0)
31.            {
32.                   shouldLoadAfterFade = false;
33.                   SceneManager.LoadScene(areaToLoad);
34.            }
35.         }
36.     }
37.  
38.     private void OnTriggerEnter2D(Collider2D other)
39.     {
40.        if(other.tag == "Player")
41.        {
42.            //SceneManager.LoadScene(areaToLoad);
43.            shouldLoadAfterFade = true;
44.            UIFade.instance.FadeToBlack();
45.  
46.            PlayerController.instance.areaTransitionName = areaTransitionName;
47.        }
48.     }
49. }
50.  

UIFade:

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4. using UnityEngine.UI;
5.  
6. public class UIFade : MonoBehaviour
7. {
8.  
9.     public static UIFade instance;
10.  
11.     public Image fadescreen;
12.     public float fadeSpeed;
13.  
14.     public bool shouldFadeToBlack;
15.     public bool shouldFadeFromBlack;
16.  
17.     // Start is called before the first frame update
18.     void Start()
19.     {
20.        instance = this;
21.  
22.        DontDestroyOnLoad(gameObject);
23.     }
24.  
25.     // Update is called once per frame
26.     void Update()
27.     {
28.         if(shouldFadeToBlack)
29.         {
30.             fadescreen.color = new Color(fadescreen.color.r, fadescreen.color.g, fadescreen.color.b, Mathf.MoveTowards(fadescreen.color.a, 1f, fadeSpeed * Time.deltaTime));
31.  
32.             if(fadescreen.color.a == 1f)
33.             {
34.                   shouldFadeToBlack = false;
35.             }
36.         }
37.  
38.         if(shouldFadeFromBlack)
39.         {
40.             fadescreen.color = new Color(fadescreen.color.r, fadescreen.color.g, fadescreen.color.b, Mathf.MoveTowards(fadescreen.color.a, 0f, fadeSpeed * Time.deltaTime));
41.  
42.              if(fadescreen.color.a == 0f)
43.             {
44.                   shouldFadeFromBlack = false;
45.             }
46.         }
47.     }
48.  
49.     public void FadeToBlack()
50.         {
51.          shouldFadeToBlack = true;
52.          shouldFadeFromBlack = false;
53.         }
54.  
55.     public void FadeFromBlack()
56.     {
57.      shouldFadeToBlack = false;
58.      shouldFadeFromBlack = true;
59.     }
60. }
61.  
62.  

AreaEntrance:

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4.  
5. public class AreaEntrance : MonoBehaviour
6. {
7.     public string transitionName;
8.  
9.  
10.     // Start is called before the first frame update
11.     void Start()
12.     {
13.         if(transitionName == PlayerController.instance.areaTransitionName)
14.         {
15.            PlayerController.instance.transform.position = transform.position;
16.         }
17.  
18.         UIFade.instance.FadeFromBlack();
19.     }
20.  
21.     // Update is called once per frame
22.     void Update()
23.     {
24.  
25.     }
26. }
27.  

Thanks for your help

 

Didn't I just remind you of this like ten hours ago in the other post?

The answer is always the same... ALWAYS. It is the single most common error ever. Don't waste your life on this problem. Instead, learn how to fix it fast... it's EASY!!

Some notes on how to fix a NullReferenceException error in Unity3D
- also known as: Unassigned Reference Exception
- also known as: Missing Reference Exception

http://plbm.com/?p=221

The basic steps outlined above are:
- Identify what is null
- Identify why it is null
- Fix that.

Expect to see this error a LOT. It's easily the most common thing to do when working. Learn how to fix it rapidly. It's easy. See the above link for more tips.

This is the kind of mindset and thinking process you need to bring to this problem:

https://forum.unity.com/threads/why-do-my-music-ignore-the-sliders.993849/#post-6453695

Step by step, break it down, find the problem.

 

possibility A: X (this line executes on different scripts)

possibility B : maybe (when I take away the code line everything works...I think, I will check it tommorow

possibility C: X (I dont think this posibility is valid to my script)

possibility D: ? (Dont know what this means)

possibility E: X

possibility X: maybe (I hope not)

Whay deos D mean?

I REALLY appricate you helping everyone on the forum, I think alot of people are greatfull for that! You should be proud

HAPPY NEW YEAR!!

I hope you have time to give feedback

 

You might also look at the stack trace: click the console message to see the calls that happened before the one it says in the error. Sometimes there's a problem earlier in the sequence.

The main difference I see in the entrance and exit scripts is that you're trying to call UIFade in Start() in the Entrance one. It's probably not "born" yet Call it after a brief delay (0.25 seconds is usually plenty) with an Invoke() and see if it works. This has fixed problems for me many times.

Also, I'd re-work your bools in the UIFade script. If they always are opposite of each other, you only need one: shouldFadeToBlack. True? Fade to black. Else? Fade from black. And be sure to use if/else, you're using two ifs, which is wasteful as only one can be true in each Update(). For the setting functions, just have one and pass it the bool:
public void setFadeStatus(bool arg) {}

 

Im following a tutorial so I cant really customize the code too much. What do you mean with brief delay? Im new to unity

 

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4. public class AreaEntrance : MonoBehaviour
5. {
6.     public string transitionName;
7.     // Start is called before the first frame update
8.     void Start()
9.     {
10.         if(transitionName == PlayerController.instance.areaTransitionName)
11.         {
12.            PlayerController.instance.transform.position = transform.position;
13.         }
14.         Invoke("callUIFade", 0.25f);
15.     }
16.     void callUIFade() {
17.         UIFade.instance.FadeFromBlack();
18.     }
19.     // Update is called once per frame
20.     void Update()
21.     {
22.     }
23. }

 

Thanks I will try this

 

What deos invoke do?

 

Whoo boy, definitely learn how to pump the Unity online docs or you are going to have a really rough time! Google can answer that for you pronto-quicko.

 

Yeah, just felt like asking

 

Funny tho. Most off the time those null exceptions will do nothing in compiled code, other than producing Debug.Log reports. However, I 100% agree with Dekker. Preventing null exceptors is the first thing to learn and maintain. What it does is basically just:

Code (CSharp):

1. if the object exists, please do something with it.

You can't do anything to nothing, right?

 

Or it's like:
You: "Do something with this (gameObject, Component)"
Unity: "Which one? You never pointed me to it"

 

Beg to differ!! All code after the exception is NOT executed. If you were contemplating 17 things to setup your game and the 13th one threw a null reference, numbers 14, 15, and 16 aren't gonna be run.

 

But UIFade.instance works on the other scripts or maybe you meant another line of code?

 

My visual studio is a bit broken so I when I click on the console nothing happens :/ I have tried to uninstall and redownload.

 

No, was wondering if the Invoke() delay resolved the issue.

 

I will test it later today

 

It's a script execution order problem. You're setting you're UIFade Instance in Start, but also referencing it in Start in the two other scripts.

Move the code from UIFade.Start() into UIFade.Awake() and you should be okay.

 

UIFade.Start() UIFade.Awake, where did you get these codes from?

I feel like I have 10 IQ lol

 

IT WORKED! Thanks

I followed a tutorial and he used the same code but how did it work for him but not for me? The course is 3 years old tho

 

Every MonoBehaviour script has an Awake() method/function, which is guaranteed to run before any Start method/function in any other MonoBehaviour script. So it is usual to setup Instance references in Awake and access them in Start or later on in the execution order.

Using Invoke as you have in your start method is just holding back accessing the UIFade instance until (long) after it has been initialized. Although it works, it's not the best approach, and you should really try to get a handle on when to use Awake and Start and also probably how the whole script execution order works.

 

But I dont have a UIFade Start() or a UIFade Awake()

Edit: I made a void Awake in UIFade and puted "instance = this;" in it. Was that what you meant?

I fooled around a bit, AreaEntrance code UIFade.instance.FadeFromBlack deosnt give a error anymore but it deosnt do anything