状態の永続化

State Persistence

Persist state across app launches. By default this library store state as a local JSON file called data.json in the applications data directory. You can change this filename by providing another storage mechanism.

If you do not want to store your persisted app state as a JSON file you can extend PersistedStateStorage and provide your own methods for saving and loading data. E.g shared_preferences or sqflite. For those of you that are ambitious you could even store your state on the web or even in Firebase.

To change the persisted state simply modify the values in the data map. These changes will automatically be persisted to disk based on the saveTimeout given to the PersistedAppState widget. By default this value is 500 milliseconds. This timeout is used to stop disk thrashing on multiple map changes in quick succession.

Example

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

void main() => runApp(App());

class App extends StatefulWidget {
  @override
  _AppState createState() => _AppState();
}

class _AppState extends State<App> {
  TextEditingController _textController;

  @override
  Widget build(BuildContext context) {
    return PersistedAppState(
      storage: JsonFileStorage(),
      child: MaterialApp(
        title: 'Persistent TextField Example',
        theme: ThemeData(primarySwatch: Colors.indigo),
        home: Scaffold(
          appBar: AppBar(title: Text('Persistent TextField Example')),
          body: Container(
            padding: const EdgeInsets.all(32.0),
            alignment: Alignment.center,
            child: PersistedStateBuilder(
              builder: (BuildContext context, AsyncSnapshot<PersistedData> snapshot) {
                if (snapshot.hasData) {
                  if (_textController == null) {
                    _textController = TextEditingController(text: snapshot.data['text'] ?? '');
                  }
                  return TextField(
                    controller: _textController,
                    decoration: InputDecoration(
                      hintText: 'Enter some text',
                    ),
                    onChanged: (String value) => snapshot.data['text'] = value,
                  );
                } else {
                  return CircularProgressIndicator();
                }
              },
            ),
          ),
        ),
      ),
    );
  }
}