【簡単】並び替えのできるリストReorderableListViewとそのプロパティ

import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'ReorderableListView Example',
      home: HomePage(),
    );
  }
}

class HomePage extends StatefulWidget {
  const HomePage({Key? key}) : super(key: key);

  @override
  State<HomePage> createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  final List<String> _items = List.generate(20, (index) => "Item $index");

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('ReorderableListView Example'),
      ),
      body: ReorderableListView.builder(
        itemCount: _items.length,
        itemBuilder: (context, index) {
          return ListTile(
            key: ValueKey(_items[index]),
            title: Text(_items[index]),
            trailing: const Icon(Icons.drag_handle),
          );
        },
        onReorder: (oldIndex, newIndex) {
          setState(() {
            if (newIndex > oldIndex) {
              newIndex -= 1;
            }
            final item = _items.removeAt(oldIndex);
            _items.insert(newIndex, item);
          });
        },
      ),
    );
  }
}

itemCount: _items.length,
itemBuilder: (context, index) {
  return ListTile(
    key: ValueKey(_items[index]),
    title: Text(_items[index]),
    trailing: const Icon(Icons.drag_handle),
  );
},

itemCount: _items.length,

onReorder: (oldIndex, newIndex) {
  setState(() {
    // リストからoldIndexのItemを削除＆取得します
    final item = _items.removeAt(oldIndex);
    // すると、oldIndex以降のIndexが1つズレるため、
    // oldIndexよりnewIndexが大きい場合はnewIndexに-1する必要があります
    if (newIndex > oldIndex) {
      newIndex -= 1;
    }
    // 先ほど削除した際に取得したItemをnewIndexに挿入します
    _items.insert(newIndex, item);
  });
},

itemExtent: 30.0,

prototypeItem: ListTile(
  title: Text('Sample Item'),
),

proxyDecorator: (child, index, animation) {
  return Material(
    elevation: 6.0,
    color: Colors.transparent,
    shadowColor: Colors.black,
    child: child,
  );
},

buildDefaultDragHandles: false,
itemBuilder: (context, index) {
  return ListTile(
    key: ValueKey(_items[index]),
    title: Text(_items[index]),
    trailing: ReorderableDragStartListener(
      index: index,
      child: Icon(Icons.drag_handle),
    ),
  );
},

padding: const EdgeInsets.only(left: 15, right: 15, top: 5, bottom: 5),

header: Padding(
  padding: const EdgeInsets.all(16.0),
  child: Text(
    'リストのヘッダー',
    style: TextStyle(fontSize: 24, fontWeight: FontWeight.bold),
  ),
),

footer: Padding(
  padding: const EdgeInsets.all(16.0),
  child: Text(
    'リストのフッター',
    style: TextStyle(fontSize: 24, fontWeight: FontWeight.bold),
  ),
),

scrollDirection: Axis.horizontal,

reverse:true,

scrollController: _scrollController,

class _MainState extends State<HomePage> {
  final List<String> _items = List.generate(20, (index) => "Item $index");
  final ScrollController _scrollController = ScrollController();

  @override
  void initState() {
    super.initState();
    _scrollController.addListener(() {
      print("Scroll position: ${_scrollController.position.pixels}");
    });
  }

  void _scrollToTop() {
    _scrollController.animateTo(
      0.0,
      duration: Duration(seconds: 1),
      curve: Curves.easeInOut,
    );
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('先頭へ'),
        actions: [
          IconButton(
            icon: Icon(Icons.arrow_upward),
            onPressed: _scrollToTop,
          ),
        ],
      ),
      body: ReorderableListView.builder(
        itemCount: _items.length,
        itemBuilder: (context, index) {
          return ListTile(
            key: ValueKey(_items[index]),
            title: Text(_items[index]),
            trailing: ReorderableDragStartListener(
              index: index,
              child: Icon(Icons.drag_handle),
            ),
          );
        },
        scrollController: _scrollController,
        onReorder: (oldIndex, newIndex) {
          setState(() {
            if (newIndex > oldIndex) {
              newIndex -= 1;
            }
            final item = _items.removeAt(oldIndex);
            _items.insert(newIndex, item);
          });
        },
      ),
    );
  }
}

primary: false,

physics: BouncingScrollPhysics(),

shrinkWrap: true,

anchor: 0.1,

dragStartBehavior: DragStartBehavior.down,

keyboardDismissBehavior: ScrollViewKeyboardDismissBehavior.onDrag,

restorationId: 'reorderable_list', // このIDを使ってリストアなどの処理を実装する

clipBehavior: Clip.antiAlias,