GraphView: Dispose the Graph correctly

lib/core/graph.dart

@@ -174,8 +174,7 @@ class Graph extends ChangeNotifier {
       bool shouldStop = _updateGraphPositions(this);
       // print("shouldStop $shouldStop");
       if (shouldStop) {
-        layoutTimer.cancel();
+        stopLayout();
-        layoutTimer = null;
       }
     });
 
@@ -187,6 +186,11 @@ class Graph extends ChangeNotifier {
       }
     });*/
   }
+
+  void stopLayout() {
+    layoutTimer.cancel();
+    layoutTimer = null;
+  }
 }
 
 class GraphNodeLayout {

lib/screens/graph_view.dart

@@ -20,15 +20,29 @@ class _GraphViewScreenState extends State<GraphViewScreen> {
       var rootFolder = Provider.of<NotesFolderFS>(context);
       setState(() {
         graph = Graph.fromFolder(rootFolder);
-        graph.addListener(() {
+        graph.addListener(_setState);
-          setState(() {});
-        });
       });
       return Container(width: 2500, height: 2500);
     }
 
     return SafeArea(child: GraphView(graph));
   }
+
+  @override
+  void dispose() {
+    if (graph != null) {
+      graph.stopLayout();
+      graph.removeListener(_setState);
+    }
+
+    super.dispose();
+  }
+
+  void _setState() {
+    if (!mounted) return;
+
+    setState(() {});
+  }
 }
 
 class GraphView extends StatefulWidget {