I am brand new to flutter and programming in general -so please bear with me-, so I am taking a course on udemy and I stumbled with this error (The constructor being called isn't a const constructor)
This is the code :
import 'package:flutter/material.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
home: Scaffold(
appBar:AppBar(
title: Text('My First App'),
),
body: Text('This is my default text'),
),
);
}
}
Try below code hope its help to you. remove const keyword
import 'package:flutter/material.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
home: Scaffold(
appBar: AppBar(
title: Text('My First App'),
),
body: Text('This is my default text'),
),
);
}
}
Your result screen->
Related
I have reinstalled the flutter and Android Studio to my device and after that Scaffold widget is not working. It says "This method 'Scaffold' isn't defined for the type 'MyApp' "
add wrap Scaffold with MaterialApp widget
import 'package:flutter/material.dart';
void main() {
runApp(const MyApp());
}
class MyApp extends StatelessWidget {
const MyApp({super.key});
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Welcome to Flutter',
home: Scaffold(
appBar: AppBar(
title: const Text('Welcome to Flutter'),
),
body: const Center(
child: Text('Hello World'),
),
),
);
}
}
In the tutorial we see two body parameters: https://docs.flutter.dev/get-started/codelab
Like that:
body: const Center(
22
- child: Text('Hello World'),
23
+ body: Center(
24
+ child: Text(wordPair.asPascalCase),
But on the dartpad.dev I have an error:
The argument for the named parameter 'body' was already specified.
I have this code:
import 'package:flutter/material.dart';
import 'package:english_words/english_words.dart';
void main() {
runApp(const MyApp());
}
class MyApp extends StatelessWidget {
const MyApp({super.key});
#override
Widget build(BuildContext context) {
final wordPair = WordPair.random();
return MaterialApp(
title: 'Welcome to Flutter',
home: Scaffold(
appBar: AppBar(title: Text('Hello there')),
body: const Center(
child: Text('The word is'),
),
body: Center(child: Text(wordPair)),
),
);
}
}
The first snippet shows the changes made in the starter code. They don't coexist
If you look at the left you see the minus and plus sign.
I've followed some online tutorials and managed to implement ChangeNotifier when the app has a single route however none of these explain how to implement this when the app has more than one route (screen) which is rather the point!
I made an attempt to figure this out myself but when the app runs in the emulator I get a blank screen.
/* main.dart */
import 'dart:collection'; // used in test.dart
import 'package:flutter/foundation.dart'; // used in test.dart
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
class Person extends ChangeNotifier {
Person({this.firstName});
String firstName = '';
void updateName(String n) {
this.firstName = n;
notifyListeners();
}
}
void main() {
runApp(
Provider(
create: (_) => Person(firstName: 'Mark'),
child: MaterialApp(
initialRoute: '/',
routes: {
'/': (context) => HomeRoute(),
'/second': (context) => SecondRoute(),
'/third': (context) => ThirdRoute(),
},
),
)
);
}
class HomeRoute extends StatelessWidget {
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(Provider.of<Person>(context).firstName),
),
body: Center(
child: new IconButton(
icon: new Icon(Icons.favorite, color: Colors.redAccent),
iconSize: 70.0,
onPressed: () {
Navigator.of(context).pushNamed("/second");
}
),
),
);
}
}
class SecondRoute extends StatelessWidget {
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Second Page'),
),
body: Center(
child: Text(Provider.of<Person>(context).firstName),
),
);
}
}
class ThirdRoute extends StatelessWidget {
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Third Page'),
),
body: Center(
child: Text('Third Route'),
),
);
}
}
The project builds and runs with no error messages which has stumped me.
Any thoughts?
Code developed in FlutLab
I am pretty new in Dart and I have tried the following:
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter App',
home: MyHomePage(),
);
}
}
class MyHomePage extends StatelessWidget {
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Flutter App'),
),
body: Column(children: [
Card(
child: Text('CHART!!'),
),
Card(child: Text('LIST OF TX'),)
],),
);
}
}
output is:
Why the children of the column does not be placed next to each other?
Change the Column to Row if you want them to be next to each others horizontally.
To place the children next to each other use the Row widget which is very similar to Column. Please see the code below.
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter App',
home: MyHomePage(),
);
}
}
class MyHomePage extends StatelessWidget {
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Flutter App'),
),
body: Row(children: [
Card(
child: Text('CHART!!'),
),
Card(child: Text('LIST OF TX'),)
],),
);
}
}
I am learning flutter. i have made one app name chat x(title). the code is below
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
home: Scaffold(
appBar: AppBar(
title: Text('Chat X'),
),
body: Card(child: Column(children: <Widget>[
Text('hey! this one is new');
],),),
),
);
}
}
when ever i want to debug this code i get this error
Expected to find ']'.
Remove ; from Text('hey! this one is new'); or you can place a , if you want to have more widgets inside Column
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
home: Scaffold(
appBar: AppBar(
title: Text('Chat X'),
),
body: Card(child: Column(children: <Widget>[
Text('hey! this one is new'),
Text('hey! this one is second new'),
],),),
),
);
}
}
You shoud not have the ; after the Text widget. Like this:
Text('hey! this one is new')