Custom editor: display array within ReorderableList

I have a CustomEditor that displays my level builder information. It uses the UnityEditorInternal.ReorderableList to draw a list of levels with their properties in the Inspector.

Code (CSharp):

1. private void OnEnable()
2. {
3.     //Get top-level list property
4.     list = new ReorderableList(serializedObject,
5.                                 serializedObject.FindProperty("levels"),
6.                                 true, true, true, true);
7.      
8.     GUIStyle rightAlign = new GUIStyle();
9.     rightAlign.alignment = TextAnchor.UpperRight;
10.  
11.     //Draw and style list elements
12.     list.drawElementCallback =
13.     (Rect rect, int index, bool isActive, bool isFocused) => {
14.         var element = list.serializedProperty.GetArrayElementAtIndex(index);
15.         rect.y += 2;
16.  
17.         var third = rect.width / 3f;
18.  
19.         EditorGUI.LabelField(
20.             new Rect(rect.x, rect.y, 18f, EditorGUIUtility.singleLineHeight),
21.             element.FindPropertyRelative("id").intValue.ToString(), rightAlign);
22.  
23.         EditorGUI.PropertyField(
24.             new Rect(rect.x + 25f, rect.y, third - 30f, EditorGUIUtility.singleLineHeight),
25.             element.FindPropertyRelative("name"), GUIContent.none);
26.     }
27. }

So far everything works fine, but now I would like to add a property for an array within my reorderable list. When I try to use element.FindPropertyRelative like in the example above, the inspector draws an empty drop down arrow.

How can I draw array elements like the default Inspector does within my ReorderableList? If possible, I would like to stick to UnityEditorInternal.ReorderableList because it already has all the neat callbacks and most of what I need my custom Inspector to do.

Thanks for any suggestions!

 

Reviving this thread half a decade later. Did you ever figure this out? I can't get any foldout (like an array) in a ReorderableList to not draw as a blank area when expanded.

 

I probably did not back then, but future-me to the rescue, here is a working example:

Code (CSharp):

1. using System.Collections.Generic;
2. using UnityEditor;
3. using UnityEditorInternal;
4. using UnityEngine;
5.  
6. public class Test : MonoBehaviour
7. {
8.     public List<LevelData> levels;
9.  
10.     [System.Serializable]
11.     public class LevelData
12.     {
13.         public string[] names;
14.     }
15. }
16.  
17. [CustomEditor(typeof(Test))]
18. public class TestEditor : Editor
19. {
20.     private ReorderableList list;
21.  
22.     private void OnEnable()
23.     {
24.         list = new ReorderableList(
25.             serializedObject,
26.             serializedObject.FindProperty("levels"),
27.             true, true, true, true)
28.         {
29.             elementHeightCallback = ElementHeightCallback,
30.             drawElementCallback = DrawListElement
31.         };
32.     }
33.  
34.     private float ElementHeightCallback(int index)
35.     {
36.         // Set the height of each row dynamically depending on the height of the names entries.
37.         SerializedProperty namesProp = GetNamesProp(index);
38.         return EditorGUI.GetPropertyHeight(namesProp) + EditorGUIUtility.standardVerticalSpacing;
39.     }
40.  
41.     private void DrawListElement(Rect rect, int index, bool isActive, bool isFocused)
42.     {
43.         SerializedProperty namesProp = GetNamesProp(index);
44.  
45.         // By default, the array dropdown is offset to the left which intersects with
46.         // the drag handle, so we can either indent the array property or inset the rect.
47.         EditorGUI.indentLevel++;
48.  
49.         // Take note of the last argument, since this is an array,
50.         // we want to draw it with all of its children.
51.         EditorGUI.PropertyField(rect, namesProp, includeChildren: true);
52.         EditorGUI.indentLevel--;
53.     }
54.  
55.     private SerializedProperty GetNamesProp(int index)
56.     {
57.         var element = list.serializedProperty.GetArrayElementAtIndex(index);
58.         return element.FindPropertyRelative("names");
59.     }
60.  
61.     public override void OnInspectorGUI()
62.     {
63.         serializedObject.Update();
64.         list.DoLayoutList();
65.         serializedObject.ApplyModifiedProperties();
66.     }
67. }
68.