feat: add more animations examples (#345)

animations/README.md

@@ -23,6 +23,7 @@ Building blocks and patterns
 6. **CustomTweenDemo** Demonstrates how to extend `Tween`.
 7. **TweenSequenceDemo** Demonstrates how to use `TweenSequence` to build a
 button that changes between different colors.
+8. **AnimatedList** Demonstrates how to use `AnimatedList`
 
 ### Misc
 

animations/lib/main.dart

@@ -11,6 +11,7 @@ import 'src/basics/04_tweens.dart';
 import 'src/basics/05_animated_builder.dart';
 import 'src/basics/06_custom_tween.dart';
 import 'src/basics/07_tween_sequence.dart';
+import 'src/basics/08_animated_list.dart';
 import 'src/misc/card_swipe.dart';
 import 'src/misc/carousel.dart';
 import 'src/misc/expand_card.dart';
@@ -57,6 +58,10 @@ final basicDemos = [
       name: 'Tween Sequences',
       route: TweenSequenceDemo.routeName,
       builder: (context) => TweenSequenceDemo()),
+  Demo(
+      name: 'AnimatedList',
+      route: AnimatedListDemo.routeName,
+      builder: (context) => AnimatedListDemo()),
 ];
 
 final miscDemos = [

animations/lib/src/basics/08_animated_list.dart

@@ -0,0 +1,118 @@
+// Copyright 2020 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter/material.dart';
+import 'package:flutter/widgets.dart';
+
+class AnimatedListDemo extends StatefulWidget {
+  static String routeName = '/basics/08_animated_list';
+
+  _AnimatedListDemoState createState() => _AnimatedListDemoState();
+}
+
+class _AnimatedListDemoState extends State<AnimatedListDemo> {
+  final GlobalKey<AnimatedListState> _listKey = GlobalKey();
+  final listData = initialListData;
+
+  void addUser() {
+    setState(() {
+      int index = listData.length;
+      listData.add(
+        UserModel(firstName: "New", lastName: "Person"),
+      );
+      _listKey.currentState
+          .insertItem(index, duration: Duration(milliseconds: 300));
+    });
+  }
+
+  void deleteUser(int index) {
+    setState(() {
+      var user = listData.removeAt(index);
+      _listKey.currentState.removeItem(
+        index,
+        (context, animation) {
+          return FadeTransition(
+            opacity:
+                CurvedAnimation(parent: animation, curve: Interval(0.5, 1.0)),
+            child: SizeTransition(
+              sizeFactor:
+                  CurvedAnimation(parent: animation, curve: Interval(0.0, 1.0)),
+              axisAlignment: 0.0,
+              child: _buildItem(user),
+            ),
+          );
+        },
+        duration: Duration(milliseconds: 600),
+      );
+    });
+  }
+
+  Widget _buildItem(UserModel user, [int index]) {
+    return ListTile(
+      key: ValueKey<UserModel>(user),
+      title: Text(user.firstName),
+      subtitle: Text(user.lastName),
+      leading: CircleAvatar(
+        child: Icon(Icons.person),
+      ),
+      onLongPress: () => deleteUser(index),
+    );
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(
+        actions: <Widget>[
+          IconButton(
+            icon: Icon(Icons.add),
+            onPressed: addUser,
+          ),
+        ],
+      ),
+      body: SafeArea(
+        child: AnimatedList(
+          key: _listKey,
+          initialItemCount: initialListData.length,
+          itemBuilder: (context, index, animation) {
+            return FadeTransition(
+              opacity: animation,
+              child: _buildItem(listData[index], index),
+            );
+          },
+        ),
+      ),
+    );
+  }
+}
+
+class UserModel {
+  const UserModel({this.firstName, this.lastName});
+
+  final String firstName;
+  final String lastName;
+}
+
+List<UserModel> initialListData = [
+  UserModel(
+    firstName: "Govind",
+    lastName: "Dixit",
+  ),
+  UserModel(
+    firstName: "Greta",
+    lastName: "Stoll",
+  ),
+  UserModel(
+    firstName: "Monty",
+    lastName: "Carlo",
+  ),
+  UserModel(
+    firstName: "Petey",
+    lastName: "Cruiser",
+  ),
+  UserModel(
+    firstName: "Barry",
+    lastName: "Cade",
+  ),
+];