如何使 listview builder 成为 flutter 中的可重新排序的 listview（优先任务应用程序（todo 应用程序））

Question

如何将 listview 转换为 reorderedableListview 以制作优先任务应用程序

这是我的应用程序设计输出

我看到了很多解决方案，但在大多数解决方案中我发现了错误

这是初始状态代码

    class _TodoListScreenState extends State<TodoListScreen> {
      late List<Task> taskList = [];
    
      @override
      void initState() {
        super.initState();
        _updateTaskList();
      }
    
      _updateTaskList() async {
        print('--------->update');
        this.taskList = await DatabaseHelper.instance.getTaskList();
        print(taskList);
        setState(() {});
      }

这是创建 listtile 的方法

    
      Widget _buildTask(Task task) {
        return Column(
          children: [
            Padding(
              padding: const EdgeInsets.symmetric(horizontal: 25.0),
              child: ListTile(
                title: Text(
                  task.title!,
                  style: TextStyle(
                    fontSize: 18.0,
                    decoration: task.status == 0
                        ? TextDecoration.none
                        : TextDecoration.lineThrough,
                  ),
                ),
                subtitle: Text(
                  '${DateFormat.yMMMEd().format(task.date!)} • ${task.priority}',
                  style: TextStyle(
                    fontSize: 18.0,
                    decoration: task.status == 0
                        ? TextDecoration.none
                        : TextDecoration.lineThrough,
                  ),
                ),
                trailing: Checkbox(
                  onChanged: (value) {
                    task.status = value! ? 1 : 0;
                    DatabaseHelper.instance.updateTask(task);
                    _updateTaskList();
                  },
                  value: task.status == 1 ? true : false,
                  activeColor: Theme.of(context).primaryColor,
                ),
                onTap: () => Navigator.push(
                  context,
                  MaterialPageRoute(
                    builder: (context) => AddTask(
                      task: task,
                      updateTaskList: () {
                        _updateTaskList();
                      },
                    ),
                  ),
                ),
              ),
            ),
            Divider(),
          ],
        );
      }

这是构建方法

      @override
      Widget build(BuildContext context) {
        return Scaffold(
          floatingActionButton: FloatingActionButton(
            child: Icon(Icons.add),
            backgroundColor: Theme.of(context).primaryColor,
            onPressed: () => Navigator.push(
              context,
              MaterialPageRoute(
                builder: (context) => AddTask(updateTaskList: _updateTaskList),
              ),
            ),
          ),

我想在这个正文标签中创建可重新排序的列表视图

          body: ListView.builder(
            padding: EdgeInsets.symmetric(vertical: 80.0),
            itemCount: taskList.length + 1,
            itemBuilder: (BuildContext context, int index) {
              if (index == 0) {
                return Padding(
                  padding:
                      const EdgeInsets.symmetric(horizontal: 40.0, vertical: 20.0),
                  child: Column(
                    crossAxisAlignment: CrossAxisAlignment.start,
                    children: [
                      Text(
                        "My Tasks",
                        style: TextStyle(
                            fontWeight: FontWeight.bold,
                            fontSize: 40.0,
                            color: Colors.black),
                      ),
                      SizedBox(height: 15.0),
                      Text(
                        '${taskList.length} of ${taskList.where((Task task) => task.status == 1).toList().length} task complete ',
                        style: TextStyle(
                          fontWeight: FontWeight.w600,
                          fontSize: 20.0,
                          color: Colors.grey,
                        ),
                      ),
                    ],
                  ),
                );
              } else {
                return _buildTask(taskList[index - 1]);
              }
            },
          ),
        );
      }
    }

这是我要更改的全部代码

Answer 1

有一个像 ReorderableListView and library like Reorderables 这样的小部件可供您使用。

已更新

示例代码：

import 'dart:math';

import 'package:flutter/material.dart';
import 'package:reorderables/reorderables.dart';

class ReorderablesImagesPage extends StatefulWidget {
  ReorderablesImagesPage({
    Key key,
    this.title,
    @required this.size,
  }) : super(key: key);

  final String title;
  final double size;

  @override
  State<StatefulWidget> createState() => _ReorderablesImagesPageState();
}

class _ReorderablesImagesPageState extends State<ReorderablesImagesPage> {
  List<Widget> _tiles;

  int maxImageCount = 30;

  double iconSize;

  final int itemCount = 3;
  final double spacing = 8.0;
  final double runSpacing = 8.0;
  final double padding = 8.0;

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

    iconSize = ((widget.size - (itemCount - 1) * spacing - 2 * padding) / 3)
        .floor()
        .toDouble();

    _tiles = <Widget>[
      Container(
        child: Image.network('https://picsum.photos/250?random=1'),
        width: iconSize,
        height: iconSize,
      ),
      Container(
        child: Image.network('https://picsum.photos/250?random=2'),
        width: iconSize,
        height: iconSize,
      ),
      Container(
        child: Image.network('https://picsum.photos/250?random=3'),
        width: iconSize,
        height: iconSize,
      ),
      Container(
        child: Image.network('https://picsum.photos/250?random=4'),
        width: iconSize,
        height: iconSize,
      ),
      Container(
        child: Image.network('https://picsum.photos/250?random=5'),
        width: iconSize,
        height: iconSize,
      ),
      Container(
        child: Image.network('https://picsum.photos/250?random=6'),
        width: iconSize,
        height: iconSize,
      ),
      Container(
        child: Image.network('https://picsum.photos/250?random=7'),
        width: iconSize,
        height: iconSize,
      ),
      Container(
        child: Image.network('https://picsum.photos/250?random=8'),
        width: iconSize,
        height: iconSize,
      ),
      Container(
        child: Image.network('https://picsum.photos/250?random=9'),
        width: iconSize,
        height: iconSize,
      ),
    ];
  }

  @override
  Widget build(BuildContext context) {
    void _onReorder(int oldIndex, int newIndex) {
      setState(() {
        Widget row = _tiles.removeAt(oldIndex);
        _tiles.insert(newIndex, row);
      });
    }

    var wrap = ReorderableWrap(
        minMainAxisCount: itemCount,
        maxMainAxisCount: itemCount,
        spacing: spacing,
        runSpacing: runSpacing,
        padding: EdgeInsets.all(padding),
        children: _tiles,
        onReorder: _onReorder,
        onNoReorder: (int index) {
          //this callback is optional
          debugPrint(
              '${DateTime.now().toString().substring(5, 22)} reorder cancelled. index:$index');
        },
        onReorderStarted: (int index) {
          //this callback is optional
          debugPrint(
              '${DateTime.now().toString().substring(5, 22)} reorder started: index:$index');
        });

    var column = Column(
      crossAxisAlignment: CrossAxisAlignment.start,
      children: <Widget>[
        Expanded(
          child: SingleChildScrollView(
            child: wrap,
          ),
        ),
        ButtonBar(
          buttonPadding: EdgeInsets.all(16),
          alignment: MainAxisAlignment.end,
          children: <Widget>[
            if (_tiles.length > 0)
              IconButton(
                iconSize: 50,
                icon: Icon(Icons.remove_circle),
                color: Colors.teal,
                padding: const EdgeInsets.all(0.0),
                onPressed: () {
                  setState(() {
                    _tiles.removeAt(0);
                  });
                },
              ),
            if (_tiles.length < maxImageCount)
              IconButton(
                iconSize: 50,
                icon: Icon(Icons.add_circle),
                color: Colors.deepOrange,
                padding: const EdgeInsets.all(0.0),
                onPressed: () {
                  var rand = Random();
                  var newTile = Container(
                    child: Image.network(
                        'https://picsum.photos/250?random=${rand.nextInt(100)}'),
                    width: iconSize,
                    height: iconSize,
                  );
                  setState(() {
                    _tiles.add(newTile);
                  });
                },
              ),
          ],
        ),
      ],
    );

    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: column,
    );
  }
}

如何使 listview builder 成为 flutter 中的可重新排序的 listview（优先任务应用程序（todo 应用程序））

how can make listview builder to a reorderable listview in flutter (a priority task app (todo app))

flutter

listview

future

builder