when returning MaterialApp flutter shows error as follow "error: 1 required argument(s) expected, but 0 found. (not_enough_required_arguments at [demo] lib/main.dart:9)"Here is the screenshot
const _categoryName = "Cake";
const _categoryIcon = Icons.cake;
const _categoryColor = Colors.green;
import 'package:solution_02_category_widget/category.dart';
void main() {
runApp(UnitConverterApp());
}
class UnitConverterApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
debugShowCheckedModeBanner: false,
title: 'Unit Converter',
home: Scaffold(
backgroundColor: Colors.green[100],
body: Center(
child: Category(
name: _categoryName,
color: _categoryColor,
iconLocation: _categoryIcon,
),
),
),
);
}
}
You should wrap the title argument under AppBar Widget. You can in turn wrap the appBar argument inside the Scaffold. The scaffold is like an empty page that gives your app the white background. Below is a sample code implementation:
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
// debugShowMaterialGrid: true,
theme: ThemeData(
brightness: Brightness .light,
accentColor: Colors.deepPurple,
primarySwatch: Colors.deepOrange),
home: Scaffold(
appBar: AppBar(
title: Text('Some text'),
),
),
);
}
}
Your code is working fine without error if i remove the Category() widget. The below code is working fine:
import 'package:flutter/material.dart';
const _categoryName = "Cake";
const _categoryIcon = Icons.cake;
const _categoryColor = Colors.green;
void main() {
runApp(UnitConverterApp());
}
class UnitConverterApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
debugShowCheckedModeBanner: false,
title: 'Unit Converter',
home: Scaffold(
backgroundColor: Colors.green[100],
body: Center(
child: Container(),
),
),
);
}
}
Maybe the problem is in the Category() widget so if you post it i can check it for you.
Related
Here is a demonstration of the problem:
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: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MyHomePage(),
);
}
}
class MyHomePage extends StatelessWidget {
#override
Widget build(BuildContext context) {
return const Scaffold(
body: Center(
child: Text(" hello ",
style: TextStyle(
fontSize: 100,
backgroundColor: Colors.green,
)),
),
);
}
}
It shows up like this:
So far I've tried this on web and macOS targets and got the same result.
How can I make the Text widget include the space at the end?
Here's what I mean.
class MyHomePage extends StatelessWidget {
#override
Widget build(BuildContext context) {
return const Scaffold(
body: Center(
child: Container(
color: Colors.green,
child: Text(" hello ",
style: TextStyle(
fontSize: 100,
backgroundColor: Colors.green,
))),
),
);
}
}
My code is:
import 'package:flutter/material.dart';
void main() => runApp(BMICalculator());
class BMICalculator extends StatelessWidget {
#override
Widget build(BuildContext context) {
final ThemeData theme = ThemeData();
return MaterialApp(
theme: theme.copyWith(
colorScheme: theme.colorScheme.copyWith(
secondary: Colors.purple,
primary: Color(0xFF0d0f1e),
background: primaryC,
),
),
home: InputPage(),
);
}
}
class InputPage extends StatefulWidget {
#override
_InputPageState createState() => _InputPageState();
}
class _InputPageState extends State<InputPage> {
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('BMI CALCULATOR'),
),
body: Center(
child: Text('Body Text'),
),
floatingActionButton: FloatingActionButton(
child: Icon(Icons.add),
),
);
}
}
And I have no idea why the background color of my app won't turn into the black/purple color I have set for it. I am following a tutorial that was using the depricated theme: ThemeData but I can't find the reason why my background color isn't changing for the scaffold.
To set a background color for your Scaffold, you can set the scaffoldBackgroundColor in your ThemeData.
Using your example:
import 'package:flutter/material.dart';
void main() => runApp(BMICalculator());
class BMICalculator extends StatelessWidget {
#override
Widget build(BuildContext context) {
final ThemeData theme = ThemeData();
return MaterialApp(
theme: theme.copyWith(
// Pick the color here
scaffoldBackgroundColor: Colors.black,
colorScheme: theme.colorScheme.copyWith(
secondary: Colors.purple,
primary: Color(0xFF0d0f1e),
),
),
home: InputPage(),
);
}
}
class InputPage extends StatefulWidget {
#override
_InputPageState createState() => _InputPageState();
}
class _InputPageState extends State<InputPage> {
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('BMI CALCULATOR'),
),
body: Center(
child: Text('Body Text'),
),
floatingActionButton: FloatingActionButton(
onPressed: () {},
child: Icon(Icons.add),
),
);
}
}
import 'package:flutter/material.dart';
void main() {
runApp(RecipeApp());
}
class RecipeApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
final ThemeData theme = ThemeData();
return MaterialApp(
title: 'Recipe Calculator',
theme: theme.copyWith(
colorScheme: theme.colorScheme.copyWith(
primary: Colors.grey,
secondary: Colors.black,
),
),
home: const MyHomePage(title: 'Recipe Calculator'),
);
}
}
This is the current code and above is the current output as per the code, the color remains blue and white instead of grey and black
running on my emulator using your code it works, try restarting your app completely.
import 'package:flutter/material.dart';
void main() {
runApp(RecipeApp());
}
class RecipeApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
final ThemeData theme = ThemeData();
return MaterialApp(
title: 'Recipe Calculator',
theme: theme.copyWith(
colorScheme: theme.colorScheme.copyWith(
primary: Colors.grey,
secondary: Colors.black,
),
),
home: const MyHomePage(title: 'Recipe Calculator'),
);
}
}
class MyHomePage extends StatelessWidget {
final title;
const MyHomePage({this.title});
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(title),
),
);
}
}
Try below code hope its helpful to you ,I think you can used Scaffold Widget refer AppBar class here and refer Scaffold class here
return Scaffold(
appBar: AppBar(
backgroundColor: Colors.grey,//change color on your need
title: Text(
'BottomNavigationBar Sample',
),
),
body:Container(),//or your widget
);
Your result screen->
Flutter automatically provides a back button for routes that can pop, but how can I change the back button Icon theme through the whole app?
Like how can I change the normal material back icon to chevron?
Create pages without Scafold and use this method to navigate between routes.
navigateToRoute(BuildContext context, Widget page,String title) {
Navigator.push(context, MaterialPageRoute(builder: (context) => Scaffold(
appBar: AppBar(
leading:Icon(Icons.chevron_left),
title: Text(title),
),
body: page,
)));
}
You have to create a custom BackButton in that case. I'll suggest that you can create a customAppBar method and use it everywhere.
Checkout the below code.
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: ScreenOne(),
);
}
}
class ScreenOne extends StatefulWidget {
#override
_ScreenOneState createState() => _ScreenOneState();
}
class _ScreenOneState extends State<ScreenOne> {
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: customAppBar(title: Text("Screen One")),
body: Center(
child: RaisedButton(onPressed: () {
Navigator.of(context).push(MaterialPageRoute(builder: (_) => ScreenTwo()));
}),
),
);
}
}
class ScreenTwo extends StatefulWidget {
#override
_ScreenTwoState createState() => _ScreenTwoState();
}
class _ScreenTwoState extends State<ScreenTwo> {
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: customAppBar(
customBackButton: true,
title: Text("Screen Two"),
),
);
}
}
AppBar customAppBar({
Widget title,
bool customBackButton = false,
}) {
return AppBar(
leading: customBackButton ? CustomBackButton() : null,
title: title,
);
}
class CustomBackButton extends StatelessWidget {
const CustomBackButton({Key key, this.color, this.onPressed}) : super(key: key);
final Color color;
final Function onPressed;
#override
Widget build(BuildContext context) {
assert(debugCheckHasMaterialLocalizations(context));
return IconButton(
icon: Icon(Icons.arrow_back_ios),
color: color,
tooltip: MaterialLocalizations.of(context).backButtonTooltip,
onPressed: () {
if (onPressed != null) {
onPressed();
} else {
Navigator.maybePop(context);
}
},
);
}
}
Hope it helps :)
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
appBarTheme: AppBarTheme(
iconTheme: IconThemeData(
color: Colors.black,
),
),
),
home: MyHomePage(title: 'Flutter Demo Home Page'),
);[![Initially didn't put any color so it was white[![This is the image when I added appbartheme and changed color to black][1]][1]][1]
what I am trying to do is generate a GridView with flutter with the index which is defined above, but it said "Undefined name index" for some reason, can you help me with that please.
Here is the code:
import 'package:flutter/material.dart';
void main() => runApp(MyApp(items: List<String>.generate(1000, (index) => "Item $index")));
class MyApp extends StatelessWidget {
final List<String> items;
MyApp({Key key, #required this.items}) : super(key: key);
// This widget is the root of your application.
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: Scaffold(
appBar:
AppBar(title:
Text('List View Vertical'),),
body:
GridView.count(
crossAxisCount: 2,
children: List.generate(100, index)(
return Center(child: Text('Items $index',
style: Theme.of(context).textTheme.headline,),);
))
)
);
}
}
The result I expect is generating 1000 rows of gridview using the index I have already defined.
Replace your build() with this:
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: Scaffold(
appBar: AppBar(
title: Text('List View Vertical'),
),
body: GridView.count(
crossAxisCount: 2,
children: items.map((title) {
return Center(
child: Text(
'$title',
style: Theme.of(context).textTheme.headline,
),
);
}).toList(),
),
),
);
}
Change your code to use the values from the property items that your are passing.
Example:
class MyApp extends StatelessWidget {
final List<String> items;
MyApp({Key key, #required this.items}) : super(key: key);
// This widget is the root of your application.
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: Scaffold(
appBar: AppBar(
title: Text('List View Vertical'),
),
body: GridView.count(
crossAxisCount: 2,
children: items.map((text) {
return Center(
child: Text(
'$text',
style: Theme.of(context).textTheme.headline,
),
);
}).toList(),
),
),
);
}
}