Use Shared Preferences in a Flutter App to save variable values permanently

SharedPreferences allow us to save or store variable values in memory after app destroyed. Using this way you can keep values of variable even if you turned of your device. As a example flag value or a count value is a little thing, so we don't want to write lenghthy codes to store in databases, using few lines we can save these variables values. However if you want to store complex data/ relational data, you have to use databases or files(JSON, CSV or TXT).

You can visit this website to get details about how to use SharedPreferences in Dart.

This is the complete code for the Simple Poll App. I used this example app to explain SharedPreferences, ButtonBar Widget, BottomAppBar Widget and for other things.

	//In this gist you can learn how to save variable value using Shared_Preferences in Dart and Flutter.
	//this codee for simple vote cast app. I wanted to show, how you can use shared preferences in flutter and dart. This is the
	//easiest and understable way. But you can think of a way to do this differently. You can use database, file system and etc
	//to store data. I will show those in upcoming videos. This code can be optimized and change as like and dislike for yuor app.
	//This is created for the SL Coder youtube channel video tutorial by blasanka
	import 'package:flutter/material.dart';
	import 'package:shared_preferences/shared_preferences.dart';
	void main() => runApp(new MyApp());
	int _upVotes = 0, _downVotes = 0, _count = 0;
	class MyApp extends StatefulWidget {
	_HomePage createState() => new _HomePage();
	}
	class _HomePage extends State<MyApp> {
	SharedPreferences prefs;
	initState() {
	super.initState();
	init();
	}
	void init() async {
	prefs = await SharedPreferences.getInstance();
	_upVotes = prefs.getInt('upVotes');
	_downVotes = prefs.getInt('downVotes');
	_count = _upVotes + _downVotes;
	setPreviousState();
	}
	void setPreviousState() {
	setState(() {
	_upVotes;
	_downVotes;
	_count;
	});
	}
	void _increase() {
	setState(() {
	_upVotes++;
	_count++;
	});
	prefs.setInt('upVotes', _upVotes);
	}
	void _decrease() {
	setState(() {
	_downVotes++;
	_count++;
	});
	prefs.setInt('downVotes', _downVotes);
	}
	@override
	Widget build(BuildContext context) {
	return new MaterialApp(
	title: 'Poll App',
	home: new Scaffold(
	appBar: new AppBar(
	title: new Text("Poll App"),
	backgroundColor: new Color(0xFF8B1122),
	),
	body: new Center(
	child: new Column(
	mainAxisAlignment: MainAxisAlignment.center,
	children: <Widget>[
	makeATextWidget("Up Votes :", _upVotes),
	new ButtonBar(
	mainAxisSize: MainAxisSize.min,
	children: <Widget>[
	makeAButton('+1', _increase),
	makeAButton('-1', _decrease),
	],
	),
	makeATextWidget("Down Votes :", _downVotes),
	],
	),
	),
	bottomNavigationBar: new BottomAppBar(
	color: new Color(0xFF8B1122),
	child: new Text(
	'$_count votes casted',
	style: new TextStyle(
	color: Colors.white,
	),
	),
	),
	),
	);
	}
	}
	Widget makeAButton(String label, f()) {
	return new RaisedButton(
	child: new Text(label,
	style: new TextStyle(
	fontSize: 20.0,
	)),
	color: new Color(0xFF8B1122),
	textColor: Colors.white,
	padding: const EdgeInsets.symmetric(
	vertical: 15.0, horizontal: 20.0),
	elevation: 10.0,
	splashColor: Colors.white70,
	onPressed: f,
	);
	}
	Widget makeATextWidget(String txt, int value) {
	return new Text(
	"$txt : $value",
	style: new TextStyle(
	fontSize: 25.0,
	color: new Color(0xFF8B1122),
	fontWeight: FontWeight.w600,
	),
	);
	}

view raw poll_app.dart hosted with ❤ by GitHub