Shared Preferences in Flutter cannot save and read List - dart

Question

I was using some shared preferences to read and save lists but all I got is an error that goes as follows:
Launching lib/main.dart on iPhone 7 in debug mode...
Xcode build done. 4.1s
Tried calling: getString("t")
#0 Object.noSuchMethod (dart:core/runtime/libobject_patch.dart:50:5)
#1 ShareUtils.get
package:todolist2019/ShareUtils.dart:22
<asynchronous suspension>
#2 HomeScreenState.getTaskTitle
package:todolist2019/home.dart:38
#3 _AsyncAwaitCompleter.start (dart:async/runtime/libasync_patch.dart:49:6)
#4 HomeScreenState.getTaskTitle
package:todolist2019/home.dart:35
#5 HomeScreenState.build.<anonymous closure>
package:todolist2019/home.dart:97
#6 SliverChildBuilderDelegate.build
package:flutter/…/widgets/sliver.dart:398
Here is my code for home.dart, my home screen
import 'package:flutter/material.dart';
import 'package:intl/intl.dart';
import 'dart:async';
import 'package:flutter/services.dart';
import './additem.dart';
import './ShareUtils.dart';
class HomeScreen extends StatefulWidget {
#override
State<StatefulWidget> createState() {
// TODO: implement createState
return HomeScreenState();
}
}
Timer timer;
DateTime now = DateTime.now();
String formattedTime = DateFormat('kk:mm').format(now);
String formattedDate = DateFormat('EEE d MMM').format(now);
class HomeScreenState extends State<HomeScreen> {
void changeTimeAndSetPref() {
setState(() {
DateTime now = DateTime.now();
formattedTime = DateFormat('kk:mm').format(now);
formattedDate = DateFormat('EEE d MMM').format(now);
});
}
Future getTaskTitle(index) async {
shareUtils = new ShareUtils();
shareUtils.Instance();
await shareUtils.get("title"[index]);
}
void initState() {
super.initState();
// Add listeners to this class
timer = Timer.periodic(Duration(seconds: 1), (Timer t) => changeTimeAndSetPref());
}
#override
Widget build(BuildContext context) {
// TODO: implement build
SystemChrome.setEnabledSystemUIOverlays([SystemUiOverlay.bottom]);
return Scaffold(
floatingActionButton: FloatingActionButton.extended(
onPressed: () {
Navigator.push(
context,
MaterialPageRoute(builder: (context) => addItem()),
);
},
icon: Icon(Icons.add),
label: Text("Add Item"),
),
floatingActionButtonLocation: FloatingActionButtonLocation.centerFloat,
body: Column(
children: <Widget>[
Center(
//set the correct sizes
child: Card(
child: Column(
children: <Widget>[
Text(
formattedTime,
style: TextStyle(
fontSize: 50.0,
),
),
Text(
formattedDate,
style: TextStyle(
fontSize: 35.0,
),
),
Text(
"You have impending tasks",
style: TextStyle(
fontSize: 25.0,
),
)
],
),
),
),
Expanded(
child: ListView.builder(
itemBuilder: (context, index) {
var title = getTaskTitle(index).toString();
var detail = taskTitleList[index];
EdgeInsets.all(16.0);
return ListTile(
title: Text(
title,
style: TextStyle(fontSize: 20.0),
),
subtitle: Text(
detail,
style: TextStyle(fontSize: 15.0),
),
onTap: () {
final snackBar = SnackBar(
content: Text('Item Removed'),
duration: Duration(seconds: 1),
);
setState(() {
taskTextList.removeAt(index);
taskTitleList.removeAt(index);
Scaffold.of(context).showSnackBar(snackBar);
});
},
);
},
itemCount: taskTextList.length,
),
)
],
),
);
}
}
And here is my code for additem.dart
import 'package:flutter/material.dart';
import './home.dart';
import './ShareUtils.dart';
class addItem extends StatefulWidget {
#override
State<StatefulWidget> createState() {
// TODO: implement createState
return addItemState();
}
}
ShareUtils shareUtils;
var TaskTextField;
var TaskDetailField;
var taskTextList = [];
var taskTitleList = [];
var TaskIsImportant = false;
class addItemState extends State<addItem> {
#override
Widget build(BuildContext context) {
// TODO: implement build
void saveTask (key, value) async {
await shareUtils.set(key, value);
}
return Scaffold(
floatingActionButton: FloatingActionButton.extended(
onPressed: () {
Navigator.push(
context,
MaterialPageRoute(builder: (context) => HomeScreen()),
);
setState(()async {
if (TaskIsImportant) {
taskTextList.add("❗$TaskTextField");
taskTitleList.add("$TaskDetailField");
saveTask("title", taskTextList);
} else {
taskTextList.add("$TaskTextField");
taskTitleList.add("$TaskDetailField");
saveTask("title", taskTextList);
}
});
},
label: Text("Add Task"),
icon: Icon(Icons.add),
),
floatingActionButtonLocation: FloatingActionButtonLocation.centerFloat,
body: Flex(
direction: Axis.vertical,
children: <Widget>[
Flexible(
child: Container(
child: Column(
children: <Widget>[
Card(
child: Column(
children: <Widget>[
Center(
child: Text(
"Welcome!",
style: TextStyle(fontSize: 50.0),
),
),
Center(
child: Text(
"Enter your task below",
style: TextStyle(fontSize: 25.0),
),
),
],
),
),
Container(
child: TextField(
decoration: InputDecoration(
hintText: "Enter title of task to be added",
hintStyle: TextStyle(fontSize: 20.0)),
onChanged: (taskTextField) {
setState(() {
TaskTextField = taskTextField;
print(TaskTextField);
});
},
),
margin: EdgeInsets.all(16.0),
),
Container(
child: TextField(
decoration: InputDecoration(
hintText: "Enter detail of task to be added",
hintStyle: TextStyle(fontSize: 20.0)),
onChanged: (taskDetailField) {
setState(() {
TaskDetailField = taskDetailField;
print(TaskDetailField);
});
},
),
margin: EdgeInsets.all(16.0),
),
CheckboxListTile(
title: Text(
"Important",
style: TextStyle(fontSize: 25.0),
),
activeColor: Colors.blue,
value: TaskIsImportant,
onChanged: (val) {
setState(() {
TaskIsImportant = !TaskIsImportant;
print(TaskIsImportant);
});
},
),
],
),
),
)
],
));
}
}
I hope someone can help me with this error. I am running on Flutter 1.2.1. Thanks in advance!
PS: I have implemented the Akio's code and I still got errors but lesser. I have also added the first 6 lines of error message.

Answer 1

You can add "shared_preferences: ^0.4.0" at pubspec.yaml.
And Packages get.
And you make DartFile (Ex: Filename is ShareUtils
import 'package:shared_preferences/shared_preferences.dart';
import 'dart:async';
class ShareUtils {
static ShareUtils _instance;
SharedPreferences ShareSave;
factory ShareUtils() => _instance ?? new ShareUtils._();
ShareUtils._();
void Instatce() async{
ShareSave = await SharedPreferences.getInstance();
}
Future<bool> set(key, value) async{
return ShareSave.setString(key, value);
}
Future<String> get(key) async{
return ShareSave.getString(key);
}
}
And main.dart
class MyApp extends StatelessWidget {
static ShareUtils shareUtils;
#override
Widget build(BuildContext context) {
ThemeData mainTheme = new ThemeData(
primaryColor : Color.fromRGBO(20, 42, 59, 1),
buttonColor: Color.fromRGBO(0, 132, 255, 1),
accentColor: Color.fromRGBO(31, 60, 83, 1)
);
shareUtils = new ShareUtils();
shareUtils.Instatce();
MaterialApp mainApp = new MaterialApp(
title: "Your app name",
theme: mainTheme,
home: new SplashPage(),
debugShowCheckedModeBanner: true,
routes: <String, WidgetBuilder>{
"HomePage": (BuildContext context) => new HomePage(),
},
);
return mainApp;
}
}
And you can Use this at anywhere
Before to use this, add import main.dart at header
GET:
Future NextPage() async {
MyApp.shareUtils.get("token").then((token) {
print(token);
if (token == null || token == "") {
Navigator.of(context).popAndPushNamed("RegisterPage");
} else {
Navigator.of(context).popAndPushNamed("HomePage");
}
});
}
SET:
void UserInfo(code, token) async{
await MyApp.shareUtils.set("token", token);
await MyApp.shareUtils.set("code", code);
await Navigator.of(context).pushNamed("HomePage");
}
I hope help you. Thank you
In your case MyApp.shareUtils.set("state", statelist.join("#"))
And get use statelist = token.split("#");