AnimatedList doesn't animate items when inserting or removing to an index that is offscreen.

[adendiamond]

Hi there,
I have found that AnimatedList doesn't animate items when inserting or removing to an index that is offscreen, i.e. when the surrounding widgets are destroyed (and the widget itself when removing it).

Here is a dartpad to explain:
https://dartpad.dev/3b8f07c4148c78a9284c7806a0608872?
(Please note that this isn't my code, I am having the same issue in my app, this code is from https://medium.com/flutter-community/updating-data-in-an-animatedlist-in-flutter-9dbfb136e515)

Steps to reproduce:

• Click 'insert single item' 12 times.
• Scroll to bottom
• Click 'insert single item' once
  And observe how the behavior is identical to a normal ListView, no animation.

Any help is appreciated!

[HansMuller]

CC @darrenaustin

[diegoveloper]

I have a similar issue, the selected item is animated but the others are not. Check this video I captured.

Screen.Recording.2021-08-31.at.5.15.48.PM.mov

This is the code sample:

class _MainPageState extends State<MainPage> {
  final key = GlobalKey<AnimatedListState>();
  final items = List.generate(10, (index) => '$index');

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Colors.black38,
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Column(
        children: [
          SizedBox(
            height: 100,
            child: AnimatedList(
              key: key,
              initialItemCount: items.length,
              scrollDirection: Axis.horizontal,
              itemBuilder: (context, index, animation) => buildItem(items[index], index, animation),
            ),
          ),
          MaterialButton(
            child: Text(
              'Insert item',
              style: TextStyle(fontSize: 15),
            ),
            color: Colors.white,
            onPressed: () => insertItem(0, 'X'),
          ),
          MaterialButton(
            child: Text(
              'Remove item',
              style: TextStyle(fontSize: 15),
            ),
            color: Colors.white,
            onPressed: () => removeItem(0),
          ),
        ],
      ),
    );
  }

  Widget buildItem(String item, int index, Animation<double> animation) => ScaleTransition(
        scale: animation,
        key: ValueKey(item),
        child: Container(
          width: 60,
          margin: EdgeInsets.all(8),
          decoration: BoxDecoration(
            borderRadius: BorderRadius.circular(12),
            color: Colors.white,
          ),
          child: FittedBox(
            child: Text(item),
          ),
        ),
      );

  void insertItem(int index, String item) {
    items.insert(index, item);
    key.currentState.insertItem(index);
  }

  void removeItem(int index) {
    final item = items.removeAt(index);

    key.currentState.removeItem(
      index,
      (context, animation) => buildItem(item, index, animation),
    );
  }
}

And this is my flutter version:

[✓] Flutter (Channel stable, 2.2.2, on macOS 11.5.2 20G95 darwin-x64, locale en-US)

[narayananulaganathan-cred]

seems like this is not fixed yet. on 2.10.3

@diegoveloper were you able to workaround this?

[diegoveloper]

seems like this is not fixed yet. on 2.10.3

@diegoveloper were you able to workaround this?

I had to use SizeTransition https://youtu.be/KZGi5kgnjbQ?t=917

[narayananulaganathan-cred]

hey thanks @diegoveloper ! that worked!

[huycozy]

This issue is reproducible on the latest stable and master channels.

Screen.Recording.2023-03-22.at.18.32.19.mov

Sample code (be compatible with the new flutter version)

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        appBar: AppBar(title: Text('Update AnimatedList data')),
        body: BodyWidget(),
      ),
    );
  }
}

class BodyWidget extends StatefulWidget {
  @override
  BodyWidgetState createState() {
    return new BodyWidgetState();
  }
}

class BodyWidgetState extends State<BodyWidget> {
  // the GlobalKey is needed to animate the list
  final GlobalKey<AnimatedListState> _listKey = GlobalKey(); // backing data
  List<String> _data = ['Horse', 'Cow', 'Camel', 'Sheep', 'Goat'];

  @override
  Widget build(BuildContext context) {
    return Column(
      children: <Widget>[
        SizedBox(
          height: 400,
          child: AnimatedList(
            key: _listKey,
            initialItemCount: _data.length,
            itemBuilder: (context, index, animation) {
              return _buildItem(_data[index], animation);
            },
          ),
        ),
        TextButton(
          child: Text(
            'Insert single item',
            style: TextStyle(fontSize: 20),
          ),
          onPressed: () {
            _onButtonPress();
          },
        )
      ],
    );
  }

  Widget _buildItem(String item, Animation<double> animation) {
    return SizeTransition(
      sizeFactor: animation,
      child: Card(
        child: ListTile(
          title: Text(
            item,
            style: TextStyle(fontSize: 20),
          ),
        ),
      ),
    );
  }

  void _onButtonPress() {
    // replace this with method choice below
    _insertSingleItem();
  }

  void _insertSingleItem() {
    String item = "Pig";
    int insertIndex = 2;
    _data.insert(insertIndex, item);
    _listKey.currentState?.insertItem(insertIndex);
  }

  void _insertMultipleItems() {
    final items = ['Pig', 'Chichen', 'Dog'];
    int insertIndex = 2;
    _data.insertAll(insertIndex, items);
    // This is a bit of a hack because currentState doesn't have
    // an insertAll() method.
    for (int offset = 0; offset < items.length; offset++) {
      _listKey.currentState?.insertItem(insertIndex + offset);
    }
  }

  void _removeSingleItems() {
    int removeIndex = 2;
    String removedItem = _data.removeAt(removeIndex);
    // This builder is just so that the animation has something
    // to work with before it disappears from view since the
    // original has already been deleted.
    AnimatedListRemovedItemBuilder builder = (context, animation) {
      // A method to build the Card widget.
      return _buildItem(removedItem, animation);
    };
    _listKey.currentState?.removeItem(removeIndex, builder);
  }

  void _removeMultipleItems() {
    int removeIndex = 2;
    int count = 2;
    for (int i = 0; i < count; i++) {
      String removedItem = _data.removeAt(removeIndex);
      AnimatedListRemovedItemBuilder builder = (context, animation) {
        return _buildItem(removedItem, animation);
      };
      _listKey.currentState?.removeItem(removeIndex, builder);
    }
  }

  void _removeAllItems() {
    final length = _data.length;
    for (int i = length - 1; i >= 0; i--) {
      String removedItem = _data.removeAt(i);
      AnimatedListRemovedItemBuilder builder = (context, animation) {
        return _buildItem(removedItem, animation);
      };
      _listKey.currentState?.removeItem(i, builder);
    }
  }

  void _updateSingleItem() {
    final newValue = 'I like sheep';
    final index = 3;
    setState(() {
      _data[index] = newValue;
    });
  }
}

flutter doctor -v (stable and master)

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