diff --git a/ArchitectureColoredPainting/src/Editor/ElementManager.cpp b/ArchitectureColoredPainting/src/Editor/ElementManager.cpp
index 0177c31..95984c8 100644
--- a/ArchitectureColoredPainting/src/Editor/ElementManager.cpp
+++ b/ArchitectureColoredPainting/src/Editor/ElementManager.cpp
@@ -45,4 +45,26 @@ QJsonObject ElementManager::toJson() const
 	QJsonObject result;
 	result.insert("elements", elementsJson);
 	return result;
+}
+
+int ElementManager::getElementIndex(GraphicElement* pelement)
+{
+	for (int i = 0; i < elements.size(); i++)
+		if (elements[i] == pelement)
+			return i;
+	return -1;
+}
+
+int ElementManager::getLayerReferencedBy(const FolderLayerWrapper* layer)
+{
+	for (int i = 0; i < elements.size(); i++)
+        if (typeid(*elements[i]) == typeid(GroupElement)) {
+            qDebug() << ((GroupElement*)elements[i])->sourceLayer;
+            qDebug() << layer;
+            qDebug() << "------------";
+            if (((GroupElement*)elements[i])->sourceLayer == layer)
+				return i;
+        }
+			
+    return -1;
 }
\ No newline at end of file
diff --git a/ArchitectureColoredPainting/src/Editor/ElementManager.h b/ArchitectureColoredPainting/src/Editor/ElementManager.h
index 1c76067..d077d6e 100644
--- a/ArchitectureColoredPainting/src/Editor/ElementManager.h
+++ b/ArchitectureColoredPainting/src/Editor/ElementManager.h
@@ -8,6 +8,7 @@ using std::vector;
 class LayerManager;
 class GraphicElement;
 class Renderer::ElementRenderer;
+class FolderLayerWrapper;
 
 class ElementManager
 {
@@ -24,4 +25,6 @@ class ElementManager
      *  only used in initialization
      */
     GraphicElement *getElementById(int index);
+	int getElementIndex(GraphicElement* pElement);
+    int getLayerReferencedBy(const FolderLayerWrapper* layer);
 };
diff --git a/ArchitectureColoredPainting/src/Editor/LayerWrapper.cpp b/ArchitectureColoredPainting/src/Editor/LayerWrapper.cpp
index 628965b..731353f 100644
--- a/ArchitectureColoredPainting/src/Editor/LayerWrapper.cpp
+++ b/ArchitectureColoredPainting/src/Editor/LayerWrapper.cpp
@@ -30,9 +30,10 @@ PixelPath LayerWrapper::getCache()
 }
 
 // TODO: undone
-LayerWrapper::LayerWrapper(QJsonObject json, FolderLayerWrapper*parent)
+LayerWrapper::LayerWrapper(QJsonObject json, FolderLayerWrapper*parent, ElementManager* elementManager)
 {
     this->parent = parent;
+    this->elementManager = elementManager;
 	this->qTreeWidgetItem = new QTreeWidgetItem();
     auto transformJson = json.value("transform").toObject();
     property.name = json.value("name").toString();
@@ -44,7 +45,7 @@ LayerWrapper::LayerWrapper(QJsonObject json, FolderLayerWrapper*parent)
 }
 
 FolderLayerWrapper::FolderLayerWrapper(QJsonObject json, ElementManager *elementManager, FolderLayerWrapper*parent)
-    : LayerWrapper(json, parent)
+    : LayerWrapper(json, parent, elementManager)
 {
     qDebug() << json.value("name").toString() << "    " << this;
     QJsonArray childrenJson = json.value("children").toArray();
@@ -205,8 +206,8 @@ QJsonObject FolderLayerWrapper::toJson() const
 		childrenJson.push_back(child->toJson());
 	json.insert("children", childrenJson);
     json.insert("is-folder", true);
-    if(this->referencedBy != -1)
-		json.insert("referenced-by", this->referencedBy);
+    if(this->getReferencedBy() != -1)
+		json.insert("referenced-by", this->getReferencedBy());
     else
 		json.insert("referenced-by", QJsonValue());
 	return json;
@@ -218,4 +219,12 @@ QJsonObject LeafLayerWrapper::toJson() const
 	json.insert("element", wrappedElement->index);
 	json.insert("is-folder", false);
 	return json;
+}
+
+int FolderLayerWrapper::getReferencedBy()const
+{
+	if (this->elementManager != nullptr)
+		return this->elementManager->getLayerReferencedBy(this);
+	else
+		return -1;
 }
\ No newline at end of file
diff --git a/ArchitectureColoredPainting/src/Editor/LayerWrapper.h b/ArchitectureColoredPainting/src/Editor/LayerWrapper.h
index 57492a8..84e7cab 100644
--- a/ArchitectureColoredPainting/src/Editor/LayerWrapper.h
+++ b/ArchitectureColoredPainting/src/Editor/LayerWrapper.h
@@ -28,6 +28,7 @@ class LayerWrapper
   protected:
     FolderLayerWrapper* parent;
     QPointF referencePoint;
+    ElementManager* elementManager;
     // vector<LayerStyle> styles;
     // TODO: 将cache移到子类，对Leaf用ComposedPainterPath，对Folder用FolderBitmapPath
     PixelPath cache;
@@ -51,7 +52,7 @@ class LayerWrapper
     // TODO: 将QPainterPath改为BitmapPath/QImage，或者直接将其删除，绘制时直接使用BitmapPath的paint方法
     virtual PixelPath getCache();
     FolderLayerWrapper*getParent() const; // invoke by manager, then invoke parent's applyStyles
-    LayerWrapper(QJsonObject json, FolderLayerWrapper*parent);
+    LayerWrapper(QJsonObject json, FolderLayerWrapper*parent, ElementManager* elementManager=nullptr);
     LayerWrapper() = default;
     // TODO : export Function
     // virtual LayerWrapper *addChild() = 0;  // Leaf Child Only
@@ -84,6 +85,7 @@ class FolderLayerWrapper : public LayerWrapper
     void delSelf() override;
 	QTreeWidgetItem* getQTreeItem() override;
 	QJsonObject toJson() const override;
+    int getReferencedBy()const;
 };
 
 class LeafLayerWrapper : public LayerWrapper