Scene hierarchy tree view example

Assets/Editor/E07_Data.cs

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+using UnityEditor;
+using UnityEngine;
+using UnityEngine.SceneManagement;
+using UnityEngine.Experimental.UIElements;
+using UnityEditor.SceneManagement;
+using UnityEditor.Experimental.UIElements;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace UIElementsExamples
+{
+    public class E07_Data : EditorWindow
+    {
+        [MenuItem("UIElementsExamples/07_Data")]
+        public static void ShowExample()
+        {
+            E07_Data window = GetWindow<E07_Data>();
+            window.minSize = new Vector2(450, 200);
+            window.titleContent = new GUIContent("Example 7");
+        }
+
+        static VisualTreeAsset s_Asset;
+        static VisualTreeAsset asset
+        {
+            get
+            {
+                if (s_Asset == null)
+                {
+					s_Asset = Resources.Load<VisualTreeAsset>("TreeView");
+                    Debug.Assert(s_Asset != null);
+                }
+                return s_Asset;
+            }
+        }
+
+        List<int> m_ExpandedGOs;
+
+        public void OnEnable()
+        {
+            if (m_ExpandedGOs == null)
+                m_ExpandedGOs = new List<int>();
+
+            Scene scene = SceneManager.GetSceneAt(0);
+
+            var scrollView = new ScrollView();
+            scrollView.StretchToParentSize();
+
+            if (scene.IsValid())
+            {
+                GameObject[] gameObjects = scene.GetRootGameObjects();
+                RecursiveSetUp(gameObjects, scrollView.contentView);
+            }
+
+            this.GetRootVisualContainer().AddChild(scrollView);
+            this.GetRootVisualContainer().AddStyleSheetPath("TreeView");
+        }
+
+        static void UpdateName(VisualElement treeViewItem, Object data)
+        {
+            if (data == null)
+                return;
+
+            treeViewItem.Q<Label>().text = data.name;
+        }
+
+        public void UpdateChildren(VisualElement treeViewItem, Object data)
+        {            
+            Transform transform = data as Transform;           
+
+            // Might be deleted
+            if (transform == null)
+                return;
+
+            List<GameObject> gos = new List<GameObject>();
+            for (int i = 0; i < transform.childCount; i++)
+            {
+                gos.Add(transform.GetChild(i).gameObject);
+            }
+            Toggle toggle = treeViewItem.Q<Toggle>();
+			toggle.enabled = gos.Count > 0;
+			toggle.on = toggle.enabled && m_ExpandedGOs.Contains(transform.gameObject.GetInstanceID());
+
+            if (m_ExpandedGOs.Contains(transform.gameObject.GetInstanceID()))
+            {
+                RecursiveSetUp(gos, treeViewItem.Q<VisualContainer>("ChildrenContainer"));    
+            }
+        }
+
+        public void RecursiveSetUp(IEnumerable<GameObject> gameObjects, VisualContainer container)
+        {
+            var currentGOs = new List<GameObject>();
+            container.ToList().ForEach((e) => {
+                GameObject go = e.data as GameObject;
+
+                // remove gone objects
+                if (go == null || !gameObjects.Contains(go))
+                {
+                    container.RemoveChild(e);
+                }
+                // or-remember those that already have an item
+                else
+                {
+                    currentGOs.Add(go);
+                }
+            });
+
+
+            foreach(GameObject go in gameObjects.Except(currentGOs))
+            {
+                VisualContainer added = asset.CloneTree();
+                added.data = go;
+
+                UpdateName(added, go);
+                added.RegisterWatch(go, UpdateName);
+				UpdateChildren(added, go.transform);
+				added.RegisterWatch(go.transform, UpdateChildren);
+
+				added.Q<Toggle>().OnToggle(() =>
+				{
+                    OnToggle(added);
+				});
+
+                container.AddChild(added);
+			}
+
+            container.Sort((a, b) => {
+                Transform aTrans = (a.data as GameObject).transform;
+                Transform bTrans = (b.data as GameObject).transform;
+                Debug.Assert(aTrans.parent == bTrans.parent);
+				int order = aTrans.GetSiblingIndex() - bTrans.GetSiblingIndex(); 
+                return order;
+            });
+        }
+
+        void OnToggle(VisualContainer treeViewItem)
+        {
+			GameObject go = treeViewItem.data as GameObject;
+            Debug.Assert(go != null, "No GO attached to item!");
+			if (!m_ExpandedGOs.Contains(go.GetInstanceID()))
+            {
+				m_ExpandedGOs.Add(go.GetInstanceID());
+				UpdateChildren(treeViewItem, go.transform);
+            }
+            else
+            {
+                treeViewItem.Q<VisualContainer>("ChildrenContainer").ClearChildren();
+                m_ExpandedGOs.Remove(go.GetInstanceID());
+            }
+        }
+    }
+}

Assets/Editor/Resources/TreeView.uss

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+#TitleContainer {
+	flex-direction: row;
+}
+
+#ChildrenContainer {
+	padding-left: 20px;
+}
+
+#TitleContainer > Toggle {
+	background-image: resource("Builtin Skins/DarkSkin/Images/IN foldout.png");
+}
+
+#TitleContainer > Toggle:focus, #TitleContainer Toggle:focus:active {
+	background-image: resource("Builtin Skins/DarkSkin/Images/IN foldout focus.png");
+}
+
+#TitleContainer > Toggle:active {
+	background-image: resource("Builtin Skins/DarkSkin/Images/IN foldout act.png");
+}
+
+#TitleContainer > Toggle:checked {
+	background-image: resource("Builtin Skins/DarkSkin/Images/IN foldout on.png");
+}
+
+#TitleContainer > Toggle:checked:focus {
+	background-image: resource("Builtin Skins/DarkSkin/Images/IN foldout focus on.png");
+}
+
+#TitleContainer > Toggle:checked:active:focus, #TitleContainer > Toggle:checked:active {
+	background-image: resource("Builtin Skins/DarkSkin/Images/IN foldout act on.png");
+}
+

Assets/Editor/Resources/TreeView.uxml

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+<Template id="TreeView" xmlns="UnityEngine.Experimental.UIElements">
+	<VisualContainer class="TreeView">
+		<VisualContainer name="TitleContainer">
+			<Toggle />
+			<Label text="Hello" />
+		</VisualContainer>
+		<VisualContainer name="ChildrenContainer" />
+	</VisualContainer>
+</Template>

Assets/Editor/Resources/uielementssettings.asset

@@ -0,0 +1,17 @@
+%YAML 1.1
+%TAG !u! tag:unity3d.com,2011:
+--- !u!114 &11400000
+MonoBehaviour:
+  m_ObjectHideFlags: 0
+  m_PrefabParentObject: {fileID: 0}
+  m_PrefabInternal: {fileID: 0}
+  m_GameObject: {fileID: 0}
+  m_Enabled: 1
+  m_EditorHideFlags: 1
+  m_Script: {fileID: 11995, guid: 0000000000000000e000000000000000, type: 0}
+  m_Name: uielementssettings
+  m_EditorClassIdentifier: 
+  viewTable:
+  - id: TreeView
+    viewNamespace: 
+    template: {fileID: 11400000, guid: f05a1e0d273c94b1db91b227901e714f, type: 3}

ProjectSettings/ProjectVersion.txt

@@ -1 +1 @@
-m_EditorVersion: 2017.2.0a1
+m_EditorVersion: 2017.2.0a4