Show snack bar to handling missing URL receivers - flutter

Question

I used the url_luncher package and it suggests handle the missing URL receiver in case of target platform can not handle the URL.
So I create a function to handle of onTap of CardTile widget and dial the phone number and if the target platform can not handle the request it shows a snake bar to inform the user in UI.
But I have two problems 1) if using an anonymous function I get a runtime error and my code would be wordly and long
Unhandled Exception: 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.
if use function name onTap of CardTile widget for example onTap : _urlLauncherFunction(context) I can not pass BuildContext context argument to the function and get a compile error
This expression has a type of 'void' so its value can't be used.
I could not figure out what did wrong so please guide and help me to solve this.
I paste the anonymous function version here
import 'package:flutter/material.dart';
import 'package:flutter/widgets.dart';
import 'package:url_launcher/url_launcher.dart';
void main() {
runApp(MyApp());
}
final telLaunchErrorSnackBar = SnackBar(
content:
Text('Your device can not handle this url'));
final String _myPhoneNumber = '[phone]';
//use xml scheme to trigger error otherwise it should be tel
final Uri _telUri = Uri(scheme: 'xml', path: _myPhoneNumber);
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
home: Scaffold(
body: SafeArea(
child: Column(
children: [
CircleAvatar(
backgroundImage: AssetImage('images/image.jpg'),
),
Card(
child: ListTile(
leading: Icon(
Icons.phone,
),
title: Text(
'00 123 45657',
),
onTap: () async {
String telUri = _telUri.toString();
await canLaunch(telUri)
? await launch(telUri)
: ScaffoldMessenger.of(context)
.showSnackBar(telLaunchErrorSnackBar);
},
),
),
],
),
),
),
);
}
}

Answer 1

When I code as this , flutter throw a error.
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
// This widget is the root of your application.
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
// home: MyHomePage(title: 'Flutter Demo Home Page'),
home: Scaffold(
body: SafeArea(
child: Container(
alignment: Alignment.center,
child: GestureDetector(
child: Container(
width: 100,
height: 100,
color: Colors.green,
),
onTap: (){
ScaffoldMessenger.of(context).showSnackBar(SnackBar(content: Text('content')));
},
),
),
),
),
);
}
}
then I change
...
MaterialApp(
home:Scafford(...),
)
...
to
...
MaterialApp(
home:Home(),
)
...
class Home extends StatelessWidget {
#override
Widget build(BuildContext context){
return Scaffold(...);
}
}
It works.