How to save app data after restart of an app

I was wondering how to make my app save data after restart? (The user can delete task and add new task to list, as well as check the box that the task is done. I want the app to save this data so when the user exists the app it will display all the tasks that he left the app with)

I was reading on google for few hours now, I got to [1]: https://flutter.dev/docs/cookbook/persistence/reading-writing-files This link as someone recommended on a similar post. But after reading it through I am a bit confused about where to start with my app.

Including some of my code and if you could help me I would really appreciate it as after hours of reading and watching tutorials I am still quite unsure where to start or which way of doing this is best.

My main.dart is this

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return ChangeNotifierProvider(
      create: (context) =>
          TaskData(), //changing builder: to create: fixed the errors i been having
      child: MaterialApp(
        home: TasksScreen(),
      ),
    );
  }
}

    class TaskData extends ChangeNotifier {
      List<Task> _tasks = [
        Task(name: "Sample task 1"),
        Task(name: "Sample task 2"),
        Task(name: "Sample task 3"),
      ];
    
      UnmodifiableListView<Task> get tasks {
        return UnmodifiableListView(_tasks);
      }
    
      int get taskCount {
        return _tasks.length;
      }
void addTask(String newTaskTitle) {
    final task = Task(name: newTaskTitle);
    _tasks.add(task);
    notifyListeners();
  }

  void updateTask(Task task) {
    task.toggleDone();
    notifyListeners();
  }

  void deleteTask(Task task) {
    _tasks.remove(task);
    notifyListeners();
  }

Thank you so much!

CodePudding user response：

The basic method is using the device local storage.

1 - Add the shared_preferences in your pubspec.yaml 2 - Create a class to write and read data :

import 'dart:convert';
import 'package:shared_preferences/shared_preferences.dart';

class StoreData {

  StoreData._privateConstructor();
 
  static final StoreData instance = StoreData._privateConstructor();

  Future<void> saveString(String key, String value) async {
    
    try{
      SharedPreferences pref = await SharedPreferences.getInstance();
      final encodedValue = base64.encode(utf8.encode(value));

      pref.setString(key, encodedValue);
    } catch (e){
      print('saveString ${e.toString()}');
    }
    
  }

  
  Future<String> getString(String key) async {
    
    SharedPreferences pref = await SharedPreferences.getInstance();
    final value = pref.getString(key) == null ? '' : pref.getString(key);

    if (value.length > 0) {
      final decodedValue = utf8.decode(base64.decode(value));  
      return decodedValue.toString();
    }
    
    return '';
  }
  
  Future<bool> remove(String key) async {
    SharedPreferences pref = await SharedPreferences.getInstance();
    return pref.remove(key);
  }

}

3 Use :

Save Data:

StoreData.instance.saveString('name', 'sergio');

Retrieve Data:

final String storedName = await StoreData.instance.getString('name');
print('The name is $storedName');

We have many other methods, like use a SQlite, NoSql or a Database in back-end, but the local storage is the most basic case

CodePudding user response：

What you need is a database or a document based data storage. You can store data in a local sqlite db, using sqflite plugin. Or you can store in a JSON asset file.

You can also use a server or cloud service. Firebase is pretty well integrated with flutter, but AWS and Azure are also great.

You can write the data in a text file in the asset, but that would very complicated.