Fix/free dependents (#1142)

* ✨ feat: add deactivate to deactivate flutter element of kraken.

* ✨ feat: add deactivate to WidgetElement.

* 🎨 chore: format.

* ✨ feat: add list of widgetElement.

* ✨ feat: add function to control list of WidgetElement.

* ✨ feat: init widgetElements.

* ✨ feat: treverse widget element to deactivate.

* ✨ feat: add wiget element to list when _attachWidget.

* 🎨 chore: modify type of widgetElements.

* 🎨 chore: modify widgetElements.

* 🎨 chore: del sa.

* 🎨 chore: add comment.

* ✨ feat: add deactivateWidgetElements.

* 🎨 chore: modify removeWidgetElement to _removeWidgetElement.

* 🎨 chore: remove _clearWidgetElements.

* 🎨 chore: remove _removeWidgetElement to _removeTarget.

* 🎨 chore: add comment.

kraken/lib/src/launcher/controller.dart

@@ -257,6 +257,7 @@ class KrakenViewController
     disposePage(_contextId);
 
     _clearTargets();
+
     document.dispose();
     window.dispose();
     _disposed = true;
@@ -279,6 +280,23 @@ class KrakenViewController
     return null;
   }
 
+  // Save all WidgetElement to manager life cycle.
+  final List<WidgetElement> _widgetElements = [];
+
+  void deactivateWidgetElements() {
+    _widgetElements.forEach((element) {
+      element.deactivate();
+    });
+  }
+
+  void addWidgetElement(WidgetElement widgetElement) {
+    _widgetElements.add(widgetElement);
+  }
+
+  void _removeWidgetElement(WidgetElement widgetElement) {
+    _widgetElements.remove(widgetElement);
+  }
+
   T? _getEventTargetById<T>(int targetId) {
     EventTarget? target = _eventTargets[targetId];
     if (target is T)
@@ -293,7 +311,11 @@ class KrakenViewController
 
   void _removeTarget(int targetId) {
     if (_eventTargets.containsKey(targetId)) {
-      _eventTargets.remove(targetId);
+      EventTarget? target = _eventTargets.remove(targetId);
+
+      if (target is WidgetElement) {
+        _removeWidgetElement(target);
+      }
     }
   }
 
@@ -304,6 +326,7 @@ class KrakenViewController
   void _clearTargets() {
     // Set current eventTargets to a new object, clean old targets by gc.
     _eventTargets = <int, EventTarget>{};
+    _widgetElements.clear();
   }
 
   // export Uint8List bytes from rendered result.

kraken/lib/src/widget/kraken.dart

@@ -878,6 +878,14 @@ class _KrakenState extends State<Kraken> with RouteAware {
     }
     return result;
   }
+
+  @override
+  void deactivate() {
+    // Deactivate all WidgetElements in Kraken when Kraken Widget is deactivated.
+    widget.controller!.view.deactivateWidgetElements();
+
+    super.deactivate();
+  }
 }
 
 class _KrakenRenderObjectWidget extends SingleChildRenderObjectWidget {

kraken/lib/src/widget/widget_to_element_adaptor.dart

@@ -247,11 +247,13 @@ abstract class WidgetElement extends dom.Element {
     RenderObjectElement rootFlutterElement = ownerDocument.controller.rootFlutterElement;
 
     KrakenRenderObjectToWidgetAdapter adaptor = KrakenRenderObjectToWidgetAdapter(
-        child: widget,
-        container: renderBoxModel as ContainerRenderObjectMixin<RenderBox,
-            ContainerBoxParentData<RenderBox>>
+      child: widget,
+      container: renderBoxModel as ContainerRenderObjectMixin<RenderBox,
+        ContainerBoxParentData<RenderBox>>
     );
 
+    ownerDocument.controller.view.addWidgetElement(this);
+
     Element? parentFlutterElement;
     if (parentNode is WidgetElement) {
       parentFlutterElement = (parentNode as WidgetElement).renderObjectElement;
@@ -261,6 +263,16 @@ abstract class WidgetElement extends dom.Element {
 
     renderObjectElement = adaptor.attachToRenderTree(rootFlutterElement.owner!, (parentFlutterElement ?? rootFlutterElement) as RenderObjectElement, parentFlutterElement == null);
   }
+
+  void deactivate() {
+    assert(renderObjectElement != null);
+    deactivateRecursively(renderObjectElement!);
+  }
+
+  void deactivateRecursively(Element element) {
+    element.deactivate();
+    element.visitChildren(deactivateRecursively);
+  }
 }
 
 class _KrakenAdapterWidget extends StatefulWidget {