Add equality operator to compare items

example/lib/home_page.dart

@@ -6,24 +6,7 @@ import 'package:example/utils/item_tile.dart';
 import 'package:flutter/material.dart';
 import 'package:animated_reorderable_list/animated_reorderable_list.dart';
 
-class User {
-  final String name;
-  final int index;
-
-  User({required this.name, required this.index});
-
-  // To prevent unnecessary animations when updating items in a list, it's essential to correctly implement the == operator and hashCode for your list item class.
-  // This allows the list to recognize items with the same data as equal, even if they are different instances.
-
-  @override
-  bool operator ==(Object other) {
-    if (identical(this, other)) return true;
-    return other is User && other.index == index;
-  }
-
-  @override
-  int get hashCode => index.hashCode;
-}
+import 'model/user_model.dart';
 
 class HomePage extends StatefulWidget {
   const HomePage({super.key});
@@ -43,10 +26,8 @@ class _HomePageState extends State<HomePage> {
 
   void insert() {
     addedNumber += 1;
-
     setState(() {
-      list.insert(
-          list.length, User(name: "User $addedNumber", index: addedNumber));
+      list.insert(2, User(name: "User $addedNumber", index: addedNumber));
     });
   }
 
@@ -174,7 +155,7 @@ class _HomePageState extends State<HomePage> {
                         scrollDirection: Axis.vertical,
                         itemBuilder: (BuildContext context, int index) {
                           return ItemCard(
-                              key: ValueKey(list[index]),
+                              key: ValueKey(list[index].index),
                               index: list[index].index);
                         },
                         sliverGridDelegate:
@@ -223,7 +204,7 @@ class _HomePageState extends State<HomePage> {
                         items: list,
                         itemBuilder: (BuildContext context, int index) {
                           return ItemTile(
-                              key: Key(list[index].name),
+                              key: ValueKey(list[index].index),
                               index: list[index].index);
                         },
                         enterTransition: animations,

example/lib/model/user_model.dart

@@ -0,0 +1,6 @@
+class User {
+  final String name;
+  final int index;
+
+  User({required this.name, required this.index});
+}

lib/src/animated_gridview.dart

@@ -140,6 +140,9 @@ class AnimatedGridView<E extends Object> extends StatelessWidget {
   /// transition for the widget that is built.
   final AnimatedWidgetBuilder? removeItemBuilder;
 
+  /// A function that compares two items to determine whether they are the same.
+  final bool Function(E a, E b)? isSameItem;
+
   const AnimatedGridView(
       {Key? key,
       required this.items,
@@ -161,7 +164,9 @@ class AnimatedGridView<E extends Object> extends StatelessWidget {
       this.dragStartBehavior = DragStartBehavior.start,
       this.clipBehavior = Clip.hardEdge,
       this.insertItemBuilder,
-      this.removeItemBuilder})
+      this.removeItemBuilder,
+      this.isSameItem
+      })
       : super(key: key);
 
   @override
@@ -190,7 +195,9 @@ class AnimatedGridView<E extends Object> extends StatelessWidget {
                 exitTransition: exitTransition,
                 scrollDirection: scrollDirection,
                 insertItemBuilder: insertItemBuilder,
-                removeItemBuilder: removeItemBuilder),
+                removeItemBuilder: removeItemBuilder,
+                isSameItem: isSameItem
+            ),
           ),
         ]);
   }

lib/src/animated_listview.dart

@@ -134,28 +134,33 @@ class AnimatedListView<E extends Object> extends StatelessWidget {
   /// transition for the widget that is built.
   final AnimatedWidgetBuilder? removeItemBuilder;
 
-  const AnimatedListView(
-      {Key? key,
-      required this.items,
-      required this.itemBuilder,
-      this.enterTransition,
-      this.exitTransition,
-      this.insertDuration,
-      this.removeDuration,
-      this.scrollDirection = Axis.vertical,
-      this.padding,
-      this.reverse = false,
-      this.controller,
-      this.primary,
-      this.physics,
-      this.scrollBehavior,
-      this.restorationId,
-      this.keyboardDismissBehavior = ScrollViewKeyboardDismissBehavior.manual,
-      this.dragStartBehavior = DragStartBehavior.start,
-      this.clipBehavior = Clip.hardEdge,
-      this.insertItemBuilder,
-      this.removeItemBuilder})
-      : super(key: key);
+
+  /// A function that compares two items to determine whether they are the same.
+  final bool Function(E a, E b)? isSameItem;
+
+  const AnimatedListView({
+    Key? key,
+    required this.items,
+    required this.itemBuilder,
+    this.enterTransition,
+    this.exitTransition,
+    this.insertDuration,
+    this.removeDuration,
+    this.scrollDirection = Axis.vertical,
+    this.padding,
+    this.reverse = false,
+    this.controller,
+    this.primary,
+    this.physics,
+    this.scrollBehavior,
+    this.restorationId,
+    this.keyboardDismissBehavior = ScrollViewKeyboardDismissBehavior.manual,
+    this.dragStartBehavior = DragStartBehavior.start,
+    this.clipBehavior = Clip.hardEdge,
+    this.insertItemBuilder,
+    this.removeItemBuilder,
+    this.isSameItem,
+  }) : super(key: key);
 
   @override
   Widget build(BuildContext context) {
@@ -183,6 +188,7 @@ class AnimatedListView<E extends Object> extends StatelessWidget {
               scrollDirection: scrollDirection,
               insertItemBuilder: insertItemBuilder,
               removeItemBuilder: removeItemBuilder,
+              isSameItem: isSameItem,
             ),
           ),
         ]);

lib/src/animated_reorderable_gridview.dart

@@ -179,6 +179,9 @@ class AnimatedReorderableGridView<E extends Object> extends StatelessWidget {
   /// Whether the items can be dragged by long pressing on them.
   final bool longPressDraggable;
 
+  /// A function that compares two items to determine whether they are the same.
+  final bool Function(E a, E b)? isSameItem;
+
   const AnimatedReorderableGridView({
     Key? key,
     required this.items,
@@ -206,6 +209,7 @@ class AnimatedReorderableGridView<E extends Object> extends StatelessWidget {
     this.longPressDraggable = true,
     this.insertItemBuilder,
     this.removeItemBuilder,
+    this.isSameItem
   }) : super(key: key);
 
   @override
@@ -240,6 +244,7 @@ class AnimatedReorderableGridView<E extends Object> extends StatelessWidget {
               insertItemBuilder: insertItemBuilder,
               removeItemBuilder: removeItemBuilder,
               longPressDraggable: longPressDraggable,
+              isSameItem: isSameItem,
             ),
           ),
         ]);

lib/src/animated_reorderable_listview.dart

@@ -27,7 +27,7 @@ import 'builder/motion_list_impl.dart';
 /// callback serves as a "proxy" (a substitute) for the item in the list. The proxy is
 /// created with the original list item as its child.
 
-class AnimatedReorderableListView<E extends Object> extends StatefulWidget {
+class AnimatedReorderableListView<E extends Object> extends StatelessWidget {
   /// The current list of items that this[AnimatedReorderableListView] should represent.
   final List<E> items;
 
@@ -188,8 +188,12 @@ class AnimatedReorderableListView<E extends Object> extends StatefulWidget {
   /// transition for the widget that is built.
   final AnimatedWidgetBuilder? removeItemBuilder;
 
+  /// Whether the items can be dragged by long pressing on them.
   final bool longPressDraggable;
 
+  /// A function that compares two items to determine whether they are the same.
+  final bool Function(E a, E b)? isSameItem;
+
   const AnimatedReorderableListView({
     Key? key,
     required this.items,
@@ -217,47 +221,42 @@ class AnimatedReorderableListView<E extends Object> extends StatefulWidget {
     this.insertItemBuilder,
     this.removeItemBuilder,
     this.longPressDraggable = true,
+    this.isSameItem,
   }) : super(key: key);
 
-  @override
-  State<AnimatedReorderableListView<E>> createState() =>
-      _AnimatedReorderableListViewState<E>();
-}
-
-class _AnimatedReorderableListViewState<E extends Object>
-    extends State<AnimatedReorderableListView<E>> {
   @override
   Widget build(BuildContext context) {
     return CustomScrollView(
-        scrollDirection: widget.scrollDirection,
-        reverse: widget.reverse,
-        controller: widget.controller,
-        primary: widget.primary,
-        physics: widget.physics,
-        scrollBehavior: widget.scrollBehavior,
-        restorationId: widget.restorationId,
-        keyboardDismissBehavior: widget.keyboardDismissBehavior,
-        dragStartBehavior: widget.dragStartBehavior,
-        clipBehavior: widget.clipBehavior,
+        scrollDirection: scrollDirection,
+        reverse: reverse,
+        controller: controller,
+        primary: primary,
+        physics: physics,
+        scrollBehavior: scrollBehavior,
+        restorationId: restorationId,
+        keyboardDismissBehavior: keyboardDismissBehavior,
+        dragStartBehavior: dragStartBehavior,
+        clipBehavior: clipBehavior,
         slivers: [
           SliverPadding(
-            padding: widget.padding ?? EdgeInsets.zero,
+            padding: padding ?? EdgeInsets.zero,
             sliver: MotionListImpl(
-              items: widget.items,
-              itemBuilder: widget.itemBuilder,
-              enterTransition: widget.enterTransition,
-              exitTransition: widget.exitTransition,
-              insertDuration: widget.insertDuration,
-              removeDuration: widget.removeDuration,
-              onReorder: widget.onReorder,
-              onReorderStart: widget.onReorderStart,
-              onReorderEnd: widget.onReorderEnd,
-              proxyDecorator: widget.proxyDecorator,
-              buildDefaultDragHandles: widget.buildDefaultDragHandles,
-              scrollDirection: widget.scrollDirection,
-              insertItemBuilder: widget.insertItemBuilder,
-              removeItemBuilder: widget.removeItemBuilder,
-              longPressDraggable: widget.longPressDraggable,
+              items: items,
+              itemBuilder: itemBuilder,
+              enterTransition: enterTransition,
+              exitTransition: exitTransition,
+              insertDuration: insertDuration,
+              removeDuration: removeDuration,
+              onReorder: onReorder,
+              onReorderStart: onReorderStart,
+              onReorderEnd: onReorderEnd,
+              proxyDecorator: proxyDecorator,
+              buildDefaultDragHandles: buildDefaultDragHandles,
+              scrollDirection: scrollDirection,
+              insertItemBuilder: insertItemBuilder,
+              removeItemBuilder: removeItemBuilder,
+              longPressDraggable: longPressDraggable,
+              isSameItem: isSameItem,
             ),
           ),
         ]);

lib/src/builder/motion_list_base.dart

@@ -32,6 +32,7 @@ abstract class MotionListBase<W extends Widget, E extends Object>
   final AnimatedWidgetBuilder? removeItemBuilder;
   final bool? buildDefaultDragHandles;
   final bool? longPressDraggable;
+  final bool Function(E a, E b)? isSameItem;
 
   const MotionListBase(
       {Key? key,
@@ -50,7 +51,8 @@ abstract class MotionListBase<W extends Widget, E extends Object>
       this.insertItemBuilder,
       this.removeItemBuilder,
       this.buildDefaultDragHandles,
-      this.longPressDraggable})
+      this.longPressDraggable,
+      this.isSameItem})
       : super(key: key);
 }
 
@@ -129,6 +131,10 @@ abstract class MotionListBaseState<
   @protected
   bool get longPressDraggable => widget.longPressDraggable ?? false;
 
+  @nonVirtual
+  @protected
+ bool  Function(E a, E b) get isSameItem => widget.isSameItem ?? (a, b) => a == b;
+
   @override
   void initState() {
     super.initState();
@@ -192,12 +198,18 @@ abstract class MotionListBaseState<
   void calculateDiff(List oldList, List newList) {
     // Detect removed and updated items
     for (int i = oldList.length - 1; i >= 0; i--) {
+      if(isSameItem(oldList[i], newList[i])) {
+        continue;
+      }
       if (!newList.contains(oldList[i])) {
         listKey.currentState!.removeItem(i, removeItemDuration: removeDuration);
       }
     }
     // Detect added items
     for (int i = 0; i < newList.length; i++) {
+      if(isSameItem(oldList[i], newList[i])) {
+        continue;
+      }
       if (!oldList.contains(newList[i])) {
         listKey.currentState!.insertItem(i, insertDuration: insertDuration);
       }