How to collapse Hierarchy scene nodes via script?

A level consists of multiple scenes in our game. Whenever we open a level in the editor (during edit-mode), we load all scenes that belong to this level like shown in the code below:

Code (CSharp):

1. [MenuItem("Open Level/Park")]
2. static void OpenParkPrototypeMenuItem()
3. {
4.     UnityEditor.SceneManagement.EditorSceneManager.OpenScene("game_park");
5.  
6.     foreach (var addtiveScenePath in new[] { "game_park_props", "game_park_vegetation", "game_park_grass", "game_park_audio", "game_park_skyline", "and so on..." })
7.     {
8.         UnityEditor.SceneManagement.EditorSceneManager.OpenScene(addtiveScenePath, UnityEditor.SceneManagement.OpenSceneMode.Additive);
9.     }
10. }

All this works great.

The annoying thing is that Unity always expands each scene in the Hierarchy after opening it with EditorSceneManager.OpenScene().

When we open a level, we load like 10 additional scenes and then we need to collapse each of these scenes before we can actually get to the thing we want.

Is there a scripting way to collapse scenes in the Hierarchy?

 

After posting the question, I thought why not looking at Unity's source code and found the private "UnityEditor.SceneHierarchyWindow.ExpandTreeViewItem" method, which is basically doing what I need.

With a bit of reflection magic, I'm now able to collapse scene nodes in the Hierarchy window through code.

Here is the code I came up with, works with 2017_4 only, because they removed the method SearchableEditorWindow.ExpandTreeViewItem in 2018.3.

Code (CSharp):

1. static void ExpandSceneHierarchy(UnityEngine.SceneManagement.Scene scene, bool expand)
2. {
3. #if UNITY_2017_4
4.    foreach (var wnd in Resources.FindObjectsOfTypeAll<SearchableEditorWindow>())
5.    {
6.        if (wnd.GetType().Name != "SceneHierarchyWindow")
7.            continue;
8.  
9.        var method = wnd.GetType().GetMethod("ExpandTreeViewItem", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance, null, new[] { typeof(int), typeof(bool) }, null);
10.        if (method == null)
11.        {
12.            Dbg.Error(wnd, "Could not find method 'UnityEditor.SceneHierarchyWindow.ExpandTreeViewItem(int, bool)'.");
13.            return;
14.        }
15.  
16.        var field = scene.GetType().GetField("m_Handle", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance);
17.        if (field == null)
18.        {
19.            Dbg.Error(wnd, "Could not find field 'int UnityEngine.SceneManagement.Scene.m_Handle'.");
20.            return;
21.        }
22.  
23.        var sceneHandle = field.GetValue(scene);
24.        method.Invoke(wnd, new System.Object[] { sceneHandle, expand });
25.    }
26. #endif
27. }
28.  

 

Thanks for posting this as we need it as well! It would be really nice if we could get a bool expand parameter added to OpenScene() since this gets pretty annoying.

 

Sorry for the necro, but this is somethign I need so bad right now.
What can we do to get this work in Unity 2019.X or 2020.X ?

 

For 2020.1.11f a working version is:

Code (CSharp):

1. private static void SetExpanded(Scene scene, bool expand)
2. {
3.     foreach (var window in Resources.FindObjectsOfTypeAll<SearchableEditorWindow>())
4.     {
5.         if (window.GetType().Name != "SceneHierarchyWindow")
6.             continue;
7.  
8.         var method = window.GetType().GetMethod("SetExpandedRecursive",
9.             System.Reflection.BindingFlags.Public |
10.             System.Reflection.BindingFlags.NonPublic |
11.             System.Reflection.BindingFlags.Instance, null,
12.             new[] { typeof(int), typeof(bool) }, null);
13.  
14.         if (method == null)
15.         {
16.             Debug.LogError(
17.                 "Could not find method 'UnityEditor.SceneHierarchyWindow.SetExpandedRecursive(int, bool)'.");
18.             return;
19.         }
20.  
21.         var field = scene.GetType().GetField("m_Handle",
22.             System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance);
23.  
24.         if (field == null)
25.         {
26.             Debug.LogError("Could not find field 'int UnityEngine.SceneManagement.Scene.m_Handle'.");
27.             return;
28.         }
29.  
30.         var sceneHandle = field.GetValue(scene);
31.         method.Invoke(window, new[] { sceneHandle, expand });
32.     }
33. }

 

This also seems to work in 2019.4.11f1, so presumedly it's good for 2019 LTS.

 

is there any way to know if the scene is callapsed or not ?

 

This is great, thanks for sharing the code here, all that contributed!

// Wildstyle