主页 / 问题 / 1020542
Accepted
fantik
Asked:2020-09-05 15:55:52 +0000 UTC2020-09-05 15:55:52 +0000 UTC

在应用关闭时保存列表视图数据

  • 772

我有一个用颤振编写的 TODO 应用程序，我希望在关闭应用程序时保存列表视图中添加的文本。听说可以添加共享偏好，但是最近在编程，不知道怎么实现。main.dart

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


void main() => runApp(new TodoApp());


class TodoApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
        debugShowCheckedModeBanner: false,
        title: 'Todo List',
        home: new TodoList()
    );
  }
}

class TodoList extends StatefulWidget {
  @override
  createState() => new TodoListState();
}

class TodoListState extends State<TodoList> {
  String _haveStarted3Times = '';
  List<String> _todoItems = [];

  void _addTodoItem(String task) {
    if(task.length > 0) {

      setState(() => _todoItems.add(task));
    }
  }

  void _removeTodoItem(int index) {
    setState(() => _todoItems.removeAt(index));
  }

  void _promptRemoveTodoItem(int index) {
    showDialog(
        context: context,
        builder: (BuildContext context) {
          return new AlertDialog(
              title: new Text('Задача "${_todoItems[index]}" выполнена?'),
              actions: <Widget>[
                new FlatButton(
                    child: new Text('отмена'),
                    onPressed: () => Navigator.of(context).pop()
                ),
                new FlatButton(
                    child: new Text('выполнена'),
                    onPressed: () {
                      _removeTodoItem(index);
                      Navigator.of(context).pop();
                    }
                )
              ]
          );
        }
    );
  }


  Widget _buildTodoList() {
    return new ListView.builder(
      itemBuilder: (context, index) {
        if(index < _todoItems.length) {
          return _buildTodoItem(_todoItems[index], index);
        }
      },
    );
  }

  Widget _buildTodoItem(String todoText, int index) {
    return new ListTile(
        title: new Text(todoText),
        onTap: () => _promptRemoveTodoItem(index)
    );
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
          title: new Text('Todo List')
      ),
      body: _buildTodoList(),
      floatingActionButton: new FloatingActionButton(
          onPressed: _pushAddTodoScreen,
          tooltip: 'Add task',
          child: new Icon(Icons.add)
      ),
    );
  }

  void _pushAddTodoScreen() {
    // Push this page onto the stack
    Navigator.of(context).push(
        new MaterialPageRoute(
            builder: (context) {
              return new Scaffold(
                  appBar: new AppBar(
                      title: new Text('добавление задачи')
                  ),
                  body: new TextField(
                    autofocus: true,
                    onSubmitted: (val) {
                      _addTodoItem(val);
                      Navigator.pop(context); // Close the add todo screen
                    },
                    decoration: new InputDecoration(
                        hintText: 'Введите вашу задачу',
                        contentPadding: const EdgeInsets.all(16.0)
                    ),
                  )
              );
            }
        )
    );
  }
}
listview

1 个回答

  1. Best Answer

    这是一个使用Shared Preferences的简单实现示例。这段代码可以优化。我不建议使用 Shared Preferences 来存储重要数据，因为它适用于简单数据（如设置）。对于更重要的数据，您需要使用 DB。

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

void main() => runApp(new TodoApp());

class TodoApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
        debugShowCheckedModeBanner: false,
        title: 'Todo List',
        home: new TodoList());
  }
}

class TodoList extends StatefulWidget {
  @override
  createState() => new TodoListState();
}

class TodoListState extends State<TodoList> {
  String _haveStarted3Times = '';
  List<String> _todoItems = [];

  @override
  Widget build(BuildContext context) {
    _getPrefs();
    return new Scaffold(
      appBar: new AppBar(title: new Text('Todo List')),
      body: _buildTodoList(),
      floatingActionButton: new FloatingActionButton(
          onPressed: _addTodoItem,
          tooltip: 'Add task',
          child: new Icon(Icons.add)),
    );
  }

  Widget _buildTodoList() {
    return new ListView.builder(itemBuilder: (context, index) {
      if (index < _todoItems.length) {
        return _buildTodoItem(_todoItems[index], index);
      }
    });
  }

  Widget _buildTodoItem(String todoText, int index) {
    return new ListTile(
        title: new Text(todoText), onTap: () => _removeTodoItem(index));
  }

  void _addTodoItem() {
    // Push this page onto the stack
    Navigator.of(context).push(new MaterialPageRoute(builder: (context) {
      return new Scaffold(
          appBar: new AppBar(title: new Text('добавление задачи')),
          body: new TextField(
            autofocus: true,
            onSubmitted: (val) {
              _addItem(val);
              Navigator.pop(context); // Close the add todo screen
            },
            decoration: new InputDecoration(
                hintText: 'Введите вашу задачу',
                contentPadding: const EdgeInsets.all(16.0)),
          ));
    }));
  }

  void _addItem(String task) {
    if (task.length > 0) {
      setState(() => _todoItems.add(task));
      _setPrefs();
    }
  }

  void _removeTodoItem(int index) {
    showDialog(
        context: context,
        builder: (BuildContext context) {
          return new AlertDialog(
              title: new Text('Задача "${_todoItems[index]}" выполнена?'),
              actions: <Widget>[
                new FlatButton(
                    child: new Text('отмена'),
                    onPressed: () => Navigator.of(context).pop()),
                new FlatButton(
                    child: new Text('выполнена'),
                    onPressed: () {
                      _removeItem(index);
                      Navigator.of(context).pop();
                    })
              ]);
        });
  }

  void _removeItem(int index) {
    setState(() => _todoItems.removeAt(index));
    _setPrefs();
  }

  void _setPrefs() async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    prefs.setStringList('TodoList', _todoItems);
  }

  void _getPrefs() async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    if (prefs.getStringList('TodoList') != null)
      _todoItems = prefs.getStringList('TodoList');
  }
}
    • 2

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