great_list_view 0.0.6

A Flutter package that enhance the standard list view with implicit animations on changes and so on. See README.md file.

great_list_view

A Flutter package that includes a powerful, animated and reorderable list view. Just notify the list view of changes in your underlying list and the list view will automatically animate. You can also change the entire list and automatically dispatch the differences detected by the Myers alghoritm. You can also reorder items by simply long-tapping the item you want to move.

Compared to the standard AnimatedList, ReorderableListView material widgets or other thid-party libraries, this library offers more:

• no specific widget is needed, it works via Sliver, so you can include it in a CustomScrollView and eventually combine it with other slivers;
• it works without necessarily specifying a List object, but simply using a index-based builder callback;
• all changes to list view items are gathered and grouped into intervals, so for examaple you can remove a while interval of a thousand items with a single remove change;
• removal, insertion e modification animations look like on Android framework;
• it is not mandatory to provide a key for each item, although it is advisable, because everything works using only indexes;
• it also works well even with a very long list;
• the library extends SliverWithKeepAliveWidget and RenderObjectElement classes, similiar to how the standard would;
• kept alive items still work well.

This package also provides a tree adapter to create a tree view without defining a new widget for it, but simply by converting your tree data into a linear list view, animated or not. Your tree data can be any data type, just describe it using a model based on a bunch of callbacks.

Installing

Add this to your pubspec.yaml file:

dependencies:
  great_list_view: ^0.0.6

and run;

flutter packages get

Example 1

This is an example of how to use AnimatedSliverList with a ListAnimatedListDiffDispatcher, which works on List objects, to swap two lists with automated animations. The list view is even reorderable.

import 'package:flutter/material.dart';

import 'package:great_list_view/great_list_view.dart';
import 'package:worker_manager/worker_manager.dart';

void main() async {
  await Executor().warmUp();
  runApp(MyApp());
}

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
        title: 'Test App',
        theme: ThemeData(
          primarySwatch: Colors.yellow,
          visualDensity: VisualDensity.adaptivePlatformDensity,
        ),
        home: SafeArea(
            child: Scaffold(
          body: MyListView(),
        )));
  }
}

class MyItem {
  final int id;
  final Color color;
  final double fixedHeight;
  const MyItem(this.id, [this.color = Colors.blue, this.fixedHeight]);
}

Widget buildItem(BuildContext context, MyItem item, int index,
    AnimatedListBuildType buildType) {
  return GestureDetector(
      onTap: click,
      child: SizedBox(
          height: item.fixedHeight,
          child: DecoratedBox(
              key: buildType == AnimatedListBuildType.NORMAL
                  ? ValueKey(item)
                  : null,
              decoration: BoxDecoration(
                  border: Border.all(color: Colors.black12, width: 0)),
              child: Container(
                  color: item.color,
                  margin: EdgeInsets.all(5),
                  padding: EdgeInsets.all(15),
                  child: Center(
                      child: Text(
                    'Item ${item.id}',
                    style: TextStyle(fontSize: 16),
                  ))))));
}

List<MyItem> listA = [
  MyItem(1, Colors.orange),
  MyItem(2),
  MyItem(3),
  MyItem(4),
  MyItem(5),
  MyItem(8, Colors.green)
];
List<MyItem> listB = [
  MyItem(2),
  MyItem(6),
  MyItem(5, Colors.pink, 100),
  MyItem(7),
  MyItem(8, Colors.yellowAccent)
];

AnimatedListController controller = AnimatedListController();

final diff = ListAnimatedListDiffDispatcher<MyItem>(
  animatedListController: controller,
  currentList: listA,
  itemBuilder: buildItem,
  comparator: MyComparator.instance,
);

class MyComparator extends ListAnimatedListDiffComparator<MyItem> {
  MyComparator._();

  static MyComparator instance = MyComparator._();

  @override
  bool sameItem(MyItem a, MyItem b) => a.id == b.id;

  @override
  bool sameContent(MyItem a, MyItem b) =>
      a.color == b.color && a.fixedHeight == b.fixedHeight;
}

bool swapList = true;

void click() {
  if (swapList) {
    diff.dispatchNewList(listB);
  } else {
    diff.dispatchNewList(listA);
  }
  swapList = !swapList;
}

class MyListView extends StatefulWidget {
  @override
  _MyListViewState createState() => _MyListViewState();
}

class _MyListViewState extends State<MyListView> {
  @override
  Widget build(BuildContext context) {
    return Scrollbar(
        child: CustomScrollView(
      slivers: <Widget>[
        AnimatedSliverList(
          delegate: AnimatedSliverChildBuilderDelegate(
            (BuildContext context, int index, AnimatedListBuildType buildType, [dynamic slot]) {
              return buildItem(
                  context, diff.currentList[index], index, buildType);
            },
            childCount: () => diff.currentList.length,
            onReorderStart: (i, dx, dy) => true,
            onReorderMove: (i, j) => true,
            onReorderComplete: (i, j, slot) {
              var list = diff.currentList;
              var el = list.removeAt(i);
              list.insert(j, el);
              return true;
            },
          ),
          controller: controller,
          reorderable: true,
        )
      ],
    ));
  }
}

Example 2

This is an example of how to use TreeListAdapter with an AnimatedSliverList to create an editable and reorderable tree view widget.

import 'dart:math';

import 'package:flutter/material.dart';
import 'package:great_list_view/great_list_view.dart';
import 'package:worker_manager/worker_manager.dart';

void main() async {
  await Executor().warmUp();
  buildTree(r, root, 8, 4);
  runApp(MyApp());
}

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
        title: 'Test App',
        theme: ThemeData(
          primarySwatch: Colors.yellow,
          visualDensity: VisualDensity.adaptivePlatformDensity,
        ),
        home: SafeArea(
            child: Scaffold(
          body: TreeExample(),
        )));
  }
}

const List<String> kNames = [
  'Liam',
  'Olivia',
  'Noah',
  'Emma',
  'Oliver',
  'Ava',
  'William',
  'Sophia',
  'Elijah',
  'Isabella',
  'James',
  'Charlotte',
  'Benjamin',
  'Amelia',
  'Lucas',
  'Mia',
  'Mason',
  'Harper',
  'Ethan',
  'Evelyn'
];

Random r = Random();

class MyNode {
  final String text;
  List<MyNode> children = [];
  MyNode parent;

  MyNode(this.text);

  void add(MyNode n, [int index]) {
    (index == null) ? children.add(n) : children.insert(index, n);
    n.parent = this;
  }

  @override
  String toString() => text;
}

MyNode root = MyNode('Me');

void buildTree(Random r, MyNode node, int maxChildren, [int startWith]) {
  var n = startWith ?? (maxChildren > 0 ? r.nextInt(maxChildren) : 0);
  if (n == 0) return;
  for (var i = 0; i < n; i++) {
    var child = MyNode(kNames[r.nextInt(kNames.length)]);
    buildTree(r, child, maxChildren - 1);
    node.add(child);
  }
}

Set<MyNode> collapsedMap = {};

AnimatedListController controller = AnimatedListController();
ScrollController scrollController = ScrollController();

TreeListAdapter<MyNode> adapter = TreeListAdapter<MyNode>(
  childAt: (node, index) => node.children[index],
  childrenCount: (node) => node.children.length,
  parentOf: (node) => node.parent,
  indexOfChild: (parent, node) => parent.children.indexOf(node),
  isNodeExpanded: (node) => !collapsedMap.contains(node),
  includeRoot: true,
  root: root,
);

class MyTreeView extends StatefulWidget {
  @override
  _MyTreeViewState createState() => _MyTreeViewState();
}

class _MyTreeViewState extends State<MyTreeView> {
  @override
  Widget build(BuildContext context) {
    return CustomScrollView(controller: scrollController, slivers: <Widget>[
      AnimatedSliverList(
          controller: controller,
          reorderable: true,
          delegate: AnimatedSliverChildBuilderDelegate(
            (BuildContext context, int index, AnimatedListBuildType buildType,
                [dynamic slot]) {
              return itemBuilder(adapter, context, index, buildType, slot);
            },
            childCount: () => adapter.count,
            onReorderStart: (index, dx, dy) {
              if (adapter.includeRoot && index == 0) return false;
              var node = adapter.indexToNode(index);
              if (!adapter.isLeaf(node) && adapter.isNodeExpanded(node)) {
                // cannot reorder an open node! the long click must first collapse it
                adapter.notifyNodeCollapsing(node, () {
                  collapsedMap.add(node);
                }, index: index, controller: controller, builder: itemBuilder);
                controller.dispatchChanges();
                return false;
              }
              return true;
            },
            onReorderFeedback: (fromIndex, toIndex, offset, dx, dy) {
              var level =
                  adapter.levelOf(adapter.indexToNode(fromIndex)) + dx ~/ 15.0;
              var levels = adapter.getPossibleLevelsOfMove(fromIndex, toIndex);
              return level.clamp(levels.from, levels.to - 1);
            },
            onReorderMove: (fromIndex, toIndex) {
              return !adapter.includeRoot || toIndex != 0;
            },
            onReorderComplete: (fromIndex, toIndex, slot) {
              adapter.moveNode(
                fromIndex,
                toIndex,
                slot as int,
                (pNode, node) => pNode.children.remove(node),
                (pNode, node, pos) => pNode.add(node, pos),
              );
              return true;
            },
          )),
    ]);
  }
}

class TreeNode extends StatefulWidget {
  final int index;
  final int level;
  final TreeListAdapter<MyNode> adapter;
  TreeNode({Key key, this.index, this.level, this.adapter}) : super(key: key);

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

class _TreeNodeState extends State<TreeNode> {
  int level;
  MyNode node;

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

  @override
  void didUpdateWidget(covariant TreeNode oldWidget) {
    super.didUpdateWidget(oldWidget);
    _update();
  }

  void _update() {
    node = widget.adapter.indexToNode(widget.index);
    level = widget.level ?? widget.adapter.levelOf(node);
  }

  @override
  Widget build(BuildContext context) {
    return ListTile(
      dense: true,
      trailing: _buildExpandCollapseArrowButton(),
      leading: _buildAddRemoveButtons(),
      title: AnimatedContainer(
        child: Text(node.toString(), style: TextStyle(fontSize: 14)),
        padding: EdgeInsets.only(left: level * 15.0),
        duration: widget.level != null
            ? const Duration(milliseconds: 250)
            : Duration.zero,
      ),
    );
  }

  Widget _buildAddRemoveButtons() {
    return SizedBox(
        width: 40,
        child: Row(
          children: [
            _buildIconButton(Colors.red, const Icon(Icons.remove), () {
              widget.adapter.notifyNodeRemoving(node, () {
                node.parent.children.remove(node);
              },
                  index: widget.index,
                  controller: controller,
                  builder: itemBuilder);
              controller.dispatchChanges();
            }),
            _buildIconButton(Colors.green, const Icon(Icons.add), () {
              var newTree = MyNode(kNames[r.nextInt(kNames.length)]);
              widget.adapter.notifyNodeInserting(newTree, node, 0, () {
                node.add(newTree, 0);
              }, index: widget.index, controller: controller);
              controller.dispatchChanges();
            }),
          ],
        ));
  }

  Widget _buildExpandCollapseArrowButton() {
    if (widget.adapter.isLeaf(node)) return null;
    return ArrowButton(
      expanded: widget.adapter.isNodeExpanded(node),
      turns: 0.25,
      icon: const Icon(Icons.keyboard_arrow_right),
      duration: const Duration(milliseconds: 500),
      onTap: (expanded) {
        if (expanded) {
          widget.adapter.notifyNodeExpanding(node, () {
            collapsedMap.remove(node);
          }, index: widget.index, controller: controller);
        } else {
          widget.adapter.notifyNodeCollapsing(node, () {
            collapsedMap.add(node);
          }, index: widget.index, controller: controller, builder: itemBuilder);
        }
        controller.dispatchChanges();
      },
    );
  }

  static Widget _buildIconButton(
      Color color, Icon icon, void Function() onPressed) {
    return DecoratedBox(
        decoration: BoxDecoration(border: Border.all(color: color, width: 2)),
        child: SizedBox(
            width: 20,
            height: 25,
            child: IconButton(
                padding: EdgeInsets.all(0.0),
                iconSize: 15,
                icon: icon,
                onPressed: onPressed)));
  }
}

Widget itemBuilder(TreeListAdapter<MyNode> adapter, BuildContext context,
    int index, AnimatedListBuildType buildType,
    [dynamic slot]) {
  return TreeNode(
    key: (buildType == AnimatedListBuildType.NORMAL)
        ? ValueKey(adapter.indexToNode(index))
        : null,
    adapter: adapter,
    index: index,
    level: buildType == AnimatedListBuildType.REORDERING ? slot as int : null,
  );
}