How could use SnackBars within the Scaffold in stateless widget? - flutter

Question

I have a class extends StatelessWidget. When try call SnackBars in Scaffold like:
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
const MyApp({super.key});
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
actions: <Widget>[
IconButton(
splashRadius: 18,
icon: const Icon(Icons.thumb_up),
tooltip: 'Like the app',
onPressed: () {
final SnackBar snackBar = SnackBar(
duration: const Duration(seconds: 1),
content: const Text('Registered as you like the application.'),
action: SnackBarAction(
label: 'Undo',
onPressed: () {},
),
);
ScaffoldMessenger.of(context).showSnackBar(snackBar);
},
),
],
title: const Text('My Application'),),
body: const Center(
child: Text("Hello World!"),)
);
}
}
when run the application show error like:
Exception has occurred.
FlutterError (No ScaffoldMessenger widget found.
MyApp widgets require a ScaffoldMessenger widget ancestor.
The specific widget that could not find a ScaffoldMessenger ancestor was:
MyApp
The ancestors of this widget were:
[root]
Typically, the ScaffoldMessenger widget is introduced by the MaterialApp at the top of your application widget tree.)

Answer 1

Wrap your app in an MaterialApp, like
void main() => runApp(MaterialApp(home: MyApp()));

Answer 2

use this code
class MyApp extends StatefulWidget {
const MyApp({super.key});
#override
State<MyApp> createState() => _MyAppState();
}
class _MyAppState extends State<MyApp> {
GlobalKey<ScaffoldMessengerState> key = GlobalKey<ScaffoldMessengerState>();
#override
Widget build(BuildContext context) {
return MaterialApp(
home: ScaffoldMessenger(
key: key,
child: Scaffold(
appBar: AppBar(
actions: <Widget>[
IconButton(
splashRadius: 18,
icon: const Icon(Icons.thumb_up),
tooltip: 'Like the app',
onPressed: () {
final snackBar = SnackBar(
content: Text(
"message",
// style: Theme.of(context).textTheme.regularWhite14,
),
duration: const Duration(seconds: 5),
action: SnackBarAction(
label: 'OK',
textColor: CustomColorScheme.whiteColor,
onPressed: () {},
),
);
key.currentState!.showSnackBar(snackBar);
},
),
],
title: const Text('My Application'),
),
body: const Center(
child: Text("Hello World!"),
)),
),
);
}
}

Answer 3

I found the answer from the youtube video as the following:
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
final _scaffoldkey = GlobalKey<ScaffoldMessengerState>();
class MyApp extends StatelessWidget {
const MyApp({super.key});
#override
Widget build(BuildContext context) {
return MaterialApp(
scaffoldMessengerKey: _scaffoldkey,
home: Scaffold(
appBar: AppBar(
actions: <Widget>[
IconButton(
splashRadius: 18,
icon: const Icon(Icons.thumb_up),
tooltip: 'Like the app',
onPressed: () {
final SnackBar snackBar = SnackBar(
duration: const Duration(seconds: 1),
content:
const Text('Registered as you like the application.'),
action: SnackBarAction(
label: 'Undo',
onPressed: () {},
),
);
ScaffoldMessengerState? scaffold = _scaffoldkey.currentState;
scaffold!.showSnackBar(snackBar);
},
),
],
title: const Text('My Application'),
),
body: const Center(
child: Text("Hello World!"),
),
),
);
}
}

Answer 4

I found the solution for the problem but first: why the error happened?
It Fails because ScaffoldMessenger.of(context) doesn't find anything above this widget's context.
the solution to use Builder class as follows:
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
const MyApp({super.key});
#override
Widget build(BuildContext context) {
return MaterialApp(
home: Scaffold(
appBar: AppBar(
actions: <Widget>[
Builder(
builder: (BuildContext context) {
return IconButton(
splashRadius: 18,
icon: const Icon(Icons.thumb_up),
tooltip: 'Like the app',
onPressed: () {
final SnackBar snackBar = SnackBar(
duration: const Duration(seconds: 1),
content: const Text(
'Registered as you like the application.'),
action: SnackBarAction(
label: 'Undo',
onPressed: () {},
),
);
ScaffoldMessenger.of(context).showSnackBar(snackBar);
},
);
},
),
],
title: const Text('My Application'),
),
body: const Center(
child: Text("Hello World!"),
)),
);
}
}