#Shared Preferencesとは
Shared Preferencesでは、データを保存・読み出しをできます。
しかし、どのようなデータでも保存できるわけではなく、保存できる型は決まっています。
保存できる型は、int型, double型, bool型, String型, String型のリストです。
まずはSharedPreferencesをインストールします。
pubspec.yaml
dependencies:
shared_preferences: ^2.0.7
全てのコード
main.dart
import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';
import 'package:untitled/class2.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
home: MyHomePage(),
);
}
}
class MyHomePage extends StatefulWidget {
@override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
int num = 0;
@override
void initState() {
super.initState();
_loadCounter();
}
_loadCounter() async {
SharedPreferences prefs = await SharedPreferences.getInstance();
setState(() {
num = (prefs.getInt('number') ?? 0);
});
}
_incrementCounter() async {
SharedPreferences prefs = await SharedPreferences.getInstance();
setState(() {
num ++;
});
prefs.setInt('number', num);
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text("title"),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text(
'$num',
style: TextStyle(
fontSize: 50,
),
),
new RaisedButton(
child: new Text("next"),
onPressed: () {
Navigator.push(context,
new MaterialPageRoute(builder: (context) => new Next()));
},
),
],
),
),
floatingActionButton: FloatingActionButton(
onPressed: _incrementCounter,
child: Icon(Icons.add),
),
);
}
}
class2.dart
import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';
class Next extends StatefulWidget {
@override
_NextState createState() => _NextState();
}
class _NextState extends State<Next> {
int num = 0;
@override
void initState() {
super.initState();
_loadCounter();
}
_loadCounter() async {
SharedPreferences prefs = await SharedPreferences.getInstance();
setState(() {
num = (prefs.getInt('number') ?? 0);
});
}
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: [
Text(
'$num',
style: TextStyle(
color: Colors.black,
fontSize: 50
),
),
RaisedButton(
onPressed: () =>
Navigator.of(context, rootNavigator: true).pop(context),
child: Text(
'pop',
style: TextStyle(
color: Colors.black
),
),)
],
),
),
);
}
}