SceneManager.LoadScene(string) doesn't work

Unity Engine
1

I’m trying to load some scenes using SceneManager but it can’t find them .

I have several 3 scenes and a static class - SystemSettings - that has a string data member m_Selected

public static void SelectScene(string selected)
    {
        if (SceneManager.GetSceneByName(selected).IsValid())
            m_Selected = selected;
        else throw new System.Exception("Scene Manager could not find scene named " + selected);
       
    }
    public static string GetSelectedSceneName()
    {
        return m_Selected;
    }

I have a main menu with a start button that is suppose to load the scene using the string given by GetSelectedSceneName() .If no scene is chosen in Settings Menu , i initalize m_Selected by default with “Town” .

public void StartSim()
    {
        SceneManager.LoadScene(SystemSettings.GetSelectedSceneName());
    }

And finally i have 3 buttons in a setting menu .Each call SelectScene using different parameters. I call the method from SystemSettings using this

public void SetSceneSelected(string selected)
    {
        SystemSettings.SelectScene(selected);
    }

Buttons OnClick + SceneManager Window - Album on Imgur Buttons OnClick params and Scene Manager window

I tried changing the names in OnClick to Scenes/[name] or “name” instead of name but the IsValid() is still false . Is there anything to be done beside adding the scenes in buildSettings ?
Also tried using int instead of string ( and therefore 0,1,2 instead of Town,City,Metropolis) .

2

Anytime you find yourself saying “This API doesn’t work!” when in fact that API is in use by MILLIONS of people around the world, it’s almost certain that you’re using it incorrectly.

First stop should be back at the documentation to make sure you’re meeting 100% of the specified requirements. Did you spell it correctly? Add it to the scene list? NOT append .unity to it? etc.

Rather than layering system on top of system on top of system (there are THREE different things in play above!), strip it down to ONE LINE OF CODE and make it work with a hard-coded scene name.

While you’re at it, be extremely explicit:

UnityEngine.SceneManagement.SceneManager.LoadScene( "MySceneName");

And you’ll find that either it works, or it gives you an error if you failed to add the MySceneName to your build settings. Make sure you’re seeing errors in the log.

Make sure your log console selector buttons are enabled. See this graphic:

Once you have contented yourself that the API does in fact work, turn your attention to your various blobs of code and start to figure out why they are NOT giving you the correct scene name, or even perhaps calling the right line of code.

What is often happening in these cases is one of the following:

  • the code you think is executing is not actually executing at all
  • the code is executing far EARLIER or LATER than you think
  • the code is executing far LESS OFTEN than you think
  • the code is executing far MORE OFTEN than you think
  • the code is executing on another GameObject than you think it is
  • you’re getting an error or warning and you haven’t noticed it in the console window

To help gain more insight into your problem, I recommend liberally sprinkling Debug.Log() statements through your code to display information in realtime.

Doing this should help you answer these types of questions:

  • is this code even running? which parts are running? how often does it run? what order does it run in?
  • what are the values of the variables involved? Are they initialized? Are the values reasonable?
  • are you meeting ALL the requirements to receive callbacks such as triggers / colliders (review the documentation)

Knowing this information will help you reason about the behavior you are seeing.

If your problem would benefit from in-scene or in-game visualization, Debug.DrawRay() or Debug.DrawLine() can help you visualize things like rays (used in raycasting) or distances.

You can also call Debug.Break() to pause the Editor when certain interesting pieces of code run, and then study the scene manually, looking for all the parts, where they are, what scripts are on them, etc.

You can also call GameObject.CreatePrimitive() to emplace debug-marker-ish objects in the scene at runtime.

You could also just display various important quantities in UI Text elements to watch them change as you play the game.

If you are running a mobile device you can also view the console output. Google for how on your particular mobile target.

Another useful approach is to temporarily strip out everything besides what is necessary to prove your issue. This can simplify and isolate compounding effects of other items in your scene or prefab.

Here’s an example of putting in a laser-focused Debug.Log() and how that can save you a TON of time wallowing around speculating what might be going wrong:

You must find a way to get the information you need in order to reason about what the problem is.

If you just need a scene utility, here’s an easy-cheesy one I use in all my games:

2 Likes
3

Firstly , thank you very much for your time and help . I agree my phrasing was not the best while trying to describe my problem and i should have emphasized more on the fact it’s me who’s not working properly . I did already try what you have told me but couldn’t really find the issue . I thought maybe it’s some less obvious button i have to press for the scene manager to recompile (and recognize the scenes) or maybe some different way to write the string parameters for onClick(). As a novice in Unity i was expecting maybe i was doing something wrong in the editor or somewhere less obvious(that’s why i posted here , maybe i was doing some small detail wrong but couldn’t see it by myself) . Finally i started once again with testing and this time i did not jump anything at all and i can tell this SceneManager.GetSceneByName(selected).IsValid() returns false despite the scene existing and loading properly . So if i do SceneManager.LoadScene(selected); immediately after (so selected has the same value in both method calls) the scene loads. So i gave up testing if the scene isValid() and now everything works as expected . Maybe a wrong call for that GetSceneByName() or IsValid() but i can’t tell why .

4

To add

I have to face the same issue but I found the solution When I create the Image component an event system was not created automatically by unity. To solve this create an event system since in order for the button or other UI object to be interactable you need to have an event system. I hope it may help.