您可以复制粘贴运行下面的完整代码
您可以保存List<RandomExpenses>作为 json 字符串randomExpensesToJson(value)
你可以得到List<RandomExpenses> with randomExpensesFromJson(keyString)
代码片段
List<RandomExpenses> randomExpensesFromJson(String str) =>
List<RandomExpenses>.from(
json.decode(str).map((x) => RandomExpenses.fromJson(x)));
String randomExpensesToJson(List<RandomExpenses> data) =>
json.encode(List<dynamic>.from(data.map((x) => x.toJson())));
...
void saveData(String key, List<RandomExpenses> value) async {
final prefs = await SharedPreferences.getInstance();
prefs.setString(key, randomExpensesToJson(value));
}
Future<List<RandomExpenses>> getData(String key) async {
final prefs = await SharedPreferences.getInstance();
String keyString = prefs.getString(key);
return Future.value(randomExpensesFromJson(keyString));
}
...
await saveData("key", randomExpensesList);
List<RandomExpenses> list = await getData("key");
print('${list[0].name} ${list[0].amount}');
print('${list[1].name} ${list[1].amount}');
output
I/flutter (24879): Rent 250
I/flutter (24879): Insurance 105
完整代码
import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';
import 'dart:convert';
List<RandomExpenses> randomExpensesFromJson(String str) =>
List<RandomExpenses>.from(
json.decode(str).map((x) => RandomExpenses.fromJson(x)));
String randomExpensesToJson(List<RandomExpenses> data) =>
json.encode(List<dynamic>.from(data.map((x) => x.toJson())));
class RandomExpenses {
String name;
int amount;
RandomExpenses({
this.name,
this.amount,
});
factory RandomExpenses.fromJson(Map<String, dynamic> json) => RandomExpenses(
name: json["name"],
amount: json["amount"],
);
Map<String, dynamic> toJson() => {
"name": name,
"amount": amount,
};
}
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
visualDensity: VisualDensity.adaptivePlatformDensity,
),
home: MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
@override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
int _counter = 0;
List<RandomExpenses> randomExpensesList = [
RandomExpenses(name: "Rent", amount: 250),
RandomExpenses(name: "Insurance", amount: 105)
];
void saveData(String key, List<RandomExpenses> value) async {
final prefs = await SharedPreferences.getInstance();
prefs.setString(key, randomExpensesToJson(value));
}
Future<List<RandomExpenses>> getData(String key) async {
final prefs = await SharedPreferences.getInstance();
String keyString = prefs.getString(key);
return Future.value(randomExpensesFromJson(keyString));
}
void _incrementCounter() async {
await saveData("key", randomExpensesList);
List<RandomExpenses> list = await getData("key");
print('${list[0].name} ${list[0].amount}');
print('${list[1].name} ${list[1].amount}');
setState(() {
_counter++;
});
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text(
'You have pushed the button this many times:',
),
Text(
'$_counter',
style: Theme.of(context).textTheme.headline4,
),
],
),
),
floatingActionButton: FloatingActionButton(
onPressed: _incrementCounter,
tooltip: 'Increment',
child: Icon(Icons.add),
),
);
}
}
