AnimatedListexample fade transition items.

main.dart

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Animation Practice',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key}) : super(key: key);

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> with TickerProviderStateMixin {
  List<String> listData = List.generate(3, (index) {
    return "New item";
  });

  GlobalKey<AnimatedListState> keyAnimatedList = GlobalKey();


  @override
  void initState() {
    super.initState();
  }

  @override
  void dispose() {
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Animation"),
      ),
      body: Container(
        color: Colors.grey[300],
        child: AnimatedList(
          key: keyAnimatedList,
          initialItemCount: listData.length,
          padding: EdgeInsets.all(16),
          itemBuilder: (BuildContext context, int index, Animation<double> animation) {
            Widget widget = FadeTransition(opacity: animation.drive(Tween<double>(begin: 0, end: 1)), child: buildRowData(listData[index]));
            return widget;
          },
        ),
      ),
      floatingActionButtonLocation: FloatingActionButtonLocation.centerFloat,
      floatingActionButton: Row(
        mainAxisSize: MainAxisSize.min,
        children: <Widget>[
          FloatingActionButton(
            backgroundColor: Colors.green[300],
            child: Icon(
              Icons.add,
            ),
            onPressed: () {
              addData();
            },
          ),
          SizedBox(
            width: 8,
          ),
          FloatingActionButton(
            backgroundColor: Colors.red[300],
            child: Icon(Icons.remove),
            onPressed: () {
              removeData();
            },
          ),
        ],
      ),
    );
  }

  void addData() {
    listData.add("New item");
    keyAnimatedList.currentState.insertItem(listData.length - 1, duration: Duration(seconds: 1));
  }

  void removeData() {
    keyAnimatedList.currentState.removeItem(listData.length - 1, (context, animation) {
      return FadeTransition(
        opacity: animation.drive(Tween(begin: 0, end: 1)),
        child: buildRowData(listData.last),
      );
    }, duration: Duration(seconds: 1));
    listData.removeLast();
  }

  Widget buildRowData(String title) {
    return Container(
      margin: EdgeInsets.symmetric(vertical: 4),
      decoration: BoxDecoration(color: Colors.white, borderRadius: BorderRadius.circular(8)),
      width: double.infinity,
      padding: EdgeInsets.all(16),
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: <Widget>[
          Text(
            title,
            style: TextStyle(fontSize: 18),
          ),
          Text(
            "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut",
            style: TextStyle(fontSize: 14, color: Colors.grey),
          ),
        ],
      ),
    );
  }
}