One time alert dialogue in Flutter - dart

Question

How do I only show an alert dialogue once? I want to have an alert dialogue appear when the user first loads a screen to show an instruction. Once the dialogue is dismissed, I do not want it to appear again.

Answer 1

You can use Shared Preferences
When launching the app, get the value from shared pref (Ex: isFirstLoaded). If isFirstLoaded == true then show the dialog.
When the dialog is dismissed, set isFirstLoaded = false and save to shared preferences.
Below is an example (please note that the example doesn't handle the dismiss event when tapping on Back key).
Add shared_preferences to your pubspec.yaml
shared_preferences: ^0.5.1+1
import 'dart:async';
import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';
void main() {
runApp(MyStatelessApp());
}
class MyStatelessApp extends StatelessWidget {
// This widget is the root of your application.
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Stateless Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: StatelessWidgetDemo(),
);
}
}
class StatelessWidgetDemo extends StatelessWidget {
final keyIsFirstLoaded = 'is_first_loaded';
#override
Widget build(BuildContext context) {
Future.delayed(Duration.zero, () => showDialogIfFirstLoaded(context));
return SafeArea(
child: Scaffold(
appBar: AppBar(
title: Text('Flutter Stateless Demo'),
),
body: Center(
child: Text('Hello'),
)));
}
showDialogIfFirstLoaded(BuildContext context) async {
SharedPreferences prefs = await SharedPreferences.getInstance();
bool isFirstLoaded = prefs.getBool(keyIsFirstLoaded);
if (isFirstLoaded == null) {
showDialog(
context: context,
builder: (BuildContext context) {
// return object of type Dialog
return AlertDialog(
title: new Text("Title"),
content: new Text("This is one time dialog"),
actions: <Widget>[
// usually buttons at the bottom of the dialog
new FlatButton(
child: new Text("Dismiss"),
onPressed: () {
// Close the dialog
Navigator.of(context).pop();
prefs.setBool(keyIsFirstLoaded, false);
},
),
],
);
},
);
}
}
}