expand bundle details and minor tweaks.

Author: alffanclub

UnityEngine.AssetBundles/Editor/AssetBundleBrowser/AssetBundleTree.cs

@@ -12,6 +12,7 @@ internal class AssetBundleTree : TreeView
     { 
         AssetBundleManageTab m_Controller;
         private bool m_ContextOnItem = false;
+        List<UnityEngine.Object> m_EmptyObjectList = new List<Object>();
 
         public AssetBundleTree(TreeViewState state, AssetBundleManageTab ctrl) : base(state)
         {
@@ -489,7 +490,7 @@ protected override void SetupDragAndDrop(SetupDragAndDropArgs args)
                 selectedBundles.Add(item.bundle);
             }
             DragAndDrop.paths = null;
-            DragAndDrop.objectReferences = new UnityEngine.Object[] { };
+            DragAndDrop.objectReferences = m_EmptyObjectList.ToArray();
             DragAndDrop.SetGenericData("AssetBundleModel.BundleInfo", selectedBundles);
             DragAndDrop.visualMode = DragAndDropVisualMode.Copy;//Move;
             DragAndDrop.StartDrag("AssetBundleTree");

UnityEngine.AssetBundles/Editor/AssetBundleBrowser/AssetListTree.cs

@@ -12,6 +12,7 @@ internal class AssetListTree : TreeView
 	{
         List<AssetBundleModel.BundleInfo> m_SourceBundles = new List<AssetBundleModel.BundleInfo>();
         AssetBundleManageTab m_Controller;
+        List<UnityEngine.Object> m_EmptyObjectList = new List<Object>();
 
         public static MultiColumnHeaderState CreateDefaultMultiColumnHeaderState()
         {
@@ -201,7 +202,11 @@ protected override void SelectionChanged(IList<int> selectedIds)
             }
             m_Controller.SetSelectedItems(selectedAssets);
         }
-        
+        protected override bool CanBeParent(TreeViewItem item)
+        {
+            return false;
+        }
+
         protected override bool CanStartDrag(CanStartDragArgs args)
         {
             args.draggedItemIDs = GetSelection();
@@ -211,10 +216,10 @@ protected override bool CanStartDrag(CanStartDragArgs args)
         protected override void SetupDragAndDrop(SetupDragAndDropArgs args)
         {
             DragAndDrop.PrepareStartDrag();
+            DragAndDrop.objectReferences = m_EmptyObjectList.ToArray();
             List<AssetBundleModel.AssetTreeItem> items = 
                 new List<AssetBundleModel.AssetTreeItem>(args.draggedItemIDs.Select(id => FindItem(id, rootItem) as AssetBundleModel.AssetTreeItem));
             DragAndDrop.paths = items.Select(a => a.asset.fullAssetName).ToArray();
-            DragAndDrop.objectReferences = new UnityEngine.Object[] { };
             DragAndDrop.SetGenericData("AssetListTreeSource", this);
             DragAndDrop.StartDrag("AssetListTree");
         }

UnityEngine.AssetBundles/Editor/AssetBundleBrowser/BundleDetailList.cs

@@ -44,7 +44,10 @@ public void Update()
                 dirty |= bundle.dirty;
             }
             if (dirty)
+            {
                 Reload();
+                ExpandAll();
+            }
         }
         protected override TreeViewItem BuildRoot()
         {
@@ -149,6 +152,7 @@ internal void SetItems(IEnumerable<AssetBundleModel.BundleInfo> items)
             }
             SetSelection(new List<int>());
             Reload();
+            ExpandAll();
         }
         internal void CollectBundles(AssetBundleModel.BundleInfo bundle)
         {