Flutter/外部ライブラリ/shared preferences

shared_preferencesとは

値を端末に保存できるライブラリ

shared_preferencesをインストール

pubspec.yaml

dependencies:
  flutter:
    sdk: flutter
  shared_preferences: ^0.5.2

flutter packages get

prefで値設定、値取得

準備

import 'package:shared_preferences/shared_preferences.dart';

数値取得

void _incrementCounter() async {
  SharedPreferences prefs = await SharedPreferences.getInstance();
  int counter = prefs.getInt('counter');
}

数値設定

void _incrementCounter() async {
  SharedPreferences prefs = await SharedPreferences.getInstance();
  await prefs.setInt('counter', 10);
}

asyncで囲む必要がある

文字列設定・取得

   String name = prefs.getString("name");
   name = "${name} ${counter}";
   await prefs.setString('name', name);

文字列リスト設定・取得

   SharedPreferences prefs = await SharedPreferences.getInstance();
   List<String> names = prefs.getStringList("textnames");
   if (names == null) {
     names = new List<String>();
   }
   names.add("new text");
   names.forEach((item) {
     print(item);
   });
   await prefs.setStringList('textnames', names);

別クラスを使う場合

lib/model/Pref.dart

import 'package:shared_preferences/shared_preferences.dart';
class Pref {
  static void saveNames(List<String> names) async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    await prefs.setStringList('textnames', names);
  }
  static Future<List<String>> getNames() async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    List<String> names = prefs.getStringList("textnames");
    if (names == null) {
      names = new List<String>();
    }
    return names;
  }
}

lib/main.dart Prefでgetしてきたものは必ずsetState((){})で囲って値を更新させて表示に反映させる

import 'model/pref.dart';
  List<String> names = new List<String>();
    Pref.getNames().then((value) {
      setState(() {
        names = value;
      });
      names.add("hogehoge");
      names.forEach((item) {
        print(item);
      });
      Pref.saveNames(names);
    });

サンプル

import 'package:shared_preferences/shared_preferences.dart';

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;
  _incrementCounter() async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    int counter = (prefs.getInt('counter') ?? 0) + 1;
    print('Pressed $counter times.');
    await prefs.setInt('counter', counter);
    setState(() {
      _counter = counter;
    });
  }
  @override
  void initState(){
    _incrementCounter();
  }
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'HelloWorld:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.display1,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}

Unhandled Exception: MissingPluginException(No implementation found for method getAll on channel plugins.flutter.io/shared_preferencesエラーが起こるとき

flutter run

参考

公式shared_preferences：https://pub.dartlang.org/packages/shared_preferences

公式shared_preferences-class：https://pub.dartlang.org/documentation/shared_preferences/latest/shared_preferences/SharedPreferences-class.html

Flutterで[key : value] 形式でローカルにデータを保存する https://qiita.com/superman9387/items/4786ba4208a546842176