Flutter UpperCamelCase - flutter

I'm new to flutter and I made my main.dart route to my splashscreen. In my main.dart, it accepted the name splashscreen() but in my splashscreen.dart it kept flagging the error "Name types using UpperCamelCase" when I named my class splashscreen.
Here is my main.dart
import 'package:flutter/material.dart';
import 'Routes/splashscreen.dart';
void main (){
runApp(MyApp());
}
class MyApp extends StatelessWidget {
MyApp ({Key? key}) : super(key: key)
#override
Widget build(BuildContext context) {
return MaterialApp(
debugShowCheckedModeBanner: false,
title: "DoyarPay",
home: splashscreen(),
);
}
}
Here is my splashscreen.dart
import 'package:flutter/material.dart';
class splashscreen extends StatefulWidget {
const splashscreen({ Key? key }) : super(key: key);
#override
_splashscreenState createState() => _splashscreenState();
}
class _splashscreenState extends State<splashscreen> {
#override
Widget build(BuildContext context) {
return Container(
);
}
}
On the splashscreen.dart it gives the "Name types using UpperCamelCase" error.
Can anyone help me out on this.
Thanks

It is "accepted" but the warning indicates that you should follow some specific naming conventions. You should definetely check here which has more details about Effective Dart.

Widgets always start with uppercase letter so change your splashscreen to Splashscreen, not only widgets but classes as well
import 'package:flutter/material.dart';
import 'Routes/splashscreen.dart';
void main (){
runApp(MyApp());
}
class MyApp extends StatelessWidget {
MyApp ({Key? key}) : super(key: key)
#override
Widget build(BuildContext context) {
return MaterialApp(
debugShowCheckedModeBanner: false,
title: "DoyarPay",
home: Splashscreen(),
);
}
}
And your splashscreen.dart
import 'package:flutter/material.dart';
class Splashscreen extends StatefulWidget {
const Splashscreen({ Key? key }) : super(key: key);
#override
_SplashscreenState createState() => _SplashscreenState();
}
class _SplashscreenState extends State<Splashscreen> {
#override
Widget build(BuildContext context) {
return Container(
);
}
}

Classes in dart has to be in UpperCamelCase.
Probably the linter doesn't detect the "error" (is not an error, you are just violating a convention) in your main.dart but it does during class declaration.
To follow dart standards just change the code using UpperCamelCase consistently:
return MaterialApp(
debugShowCheckedModeBanner: false,
title: "DoyarPay",
home: SplashScreen(),
);
import 'package:flutter/material.dart';
class SplashScreen extends StatefulWidget {
const SplashScreen({ Key? key }) : super(key: key);
#override
_SplashScreenState createState() => _SplashScreenState();
}
class _SplashScreenState extends State<SplashScreen> {
#override
Widget build(BuildContext context) {
return Container(
);
}
}

For class name in dart, suggest using CamelCase means it will start with an uppercase letter and the next word's 1st letter will be uppercase as well.
In your case splashscreen which starts with s which is lowercase. Appropriate will be SplashScreen.
For file name, we use snake_case. In this case splashscreen.dart will be splash_screen.dart
Learn more about
effective-dart
Camel case vs. snake case

Related

how to use polymorphism with provider in flutter

I try to use Polymorphism with the Provider package in Dart/Flutter, but I'm not sure if it is possible or not and if I have made a mistake.
I have two provider class "Provider1" and "Provider2" which extend an abstract class "AbstactProvider", I have a widget "WidgetProvider1Or2"
which need to interact with Provider1 Or Provider2 but flutter throw me a "ProviderNotFoundException".
thanks for yours help!
import 'package:flutter/material.dart';
import 'package:flutter_bloc/flutter_bloc.dart';
import 'package:flutter_bloc_concept/cubit/counter_cubit.dart';
import 'package:provider/provider.dart';
abstract class AbstactProvider extends ChangeNotifier {
void printName();
}
class Provider1 extends AbstactProvider {
#override
void printName() {
print("Provider1");
}
}
class Provider2 extends AbstactProvider {
#override
void printName() {
print("Provider2");
}
}
void main() {
runApp(const MyApp());
}
class MyApp extends StatelessWidget {
const MyApp({Key? key}) : super(key: key);
// This widget is the root of your application.
#override
Widget build(BuildContext context) {
return BlocProvider(
create: (context) => CounterCubit(),
child: MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: const MyHomePage(title: 'Flutter Demo Home Page'),
),
);
}
}
class MyHomePage extends StatefulWidget {
const MyHomePage({Key? key, required this.title}) : super(key: key);
final String title;
#override
State<MyHomePage> createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
#override
Widget build(BuildContext context) {
Widget widgetProvider1 = ChangeNotifierProvider(
create: (_) => Provider1(),
child: WidgetProvider1(),
);
Widget widgetProvider2 = ChangeNotifierProvider(
create: (_) => Provider2(),
child: WidgetProvider2(),
);
Widget widgetProvider1Or2 = ChangeNotifierProvider(
create: (_) => Provider1(),
child: WidgetProvider1Or2(),
);
return Scaffold(
body: Column(
children: [widgetProvider1, widgetProvider2, widgetProvider1Or2],
),
);
}
}
class WidgetProvider1 extends StatelessWidget {
const WidgetProvider1({Key? key}) : super(key: key);
#override
Widget build(BuildContext context) {
context.watch<Provider1>();
return Container();
}
}
class WidgetProvider2 extends StatelessWidget {
const WidgetProvider2({Key? key}) : super(key: key);
#override
Widget build(BuildContext context) {
context.watch<Provider2>();
return Container();
}
}
class WidgetProvider1Or2 extends StatelessWidget {
const WidgetProvider1Or2({Key? key}) : super(key: key);
#override
Widget build(BuildContext context) {
context.watch<AbstactProvider>();
return Container();
}
}

org-dartlang-app:/web_entrypoint.dart:16:22: Error: Undefined name 'main'. return (entrypoint.main as _NullaryFunction)();

hi i try to open flutter app on chrome and that what happen.org-dartlang-app:/web_entrypoint.dart:16:22: Error: Undefined name 'main'.
return (entrypoint.main as _NullaryFunction)();
my code:`
import 'package:flutter/material.dart';
class hellp extends StatefulWidget {
const hellp({ Key? key }) : super(key: key);
#override
State<hellp> createState() => _hellpState();
}
class _hellpState extends State<hellp> {
#override
Widget build( BuildContext context) {
return Container(
);
}
}
Just faced this error message while attempting to test a code snippet I found online. Mine was with a stateless widget though.
I solved it by adding the following code after the import statements:
import 'package:flutter/material.dart';
void main() { //add this
runApp(const MyApp());
}
//using stateless widget here.
class MyApp extends StatelessWidget {
const MyApp({Key? key}) : super(key: key);
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
home: const MyHomePage(),
);
}
Hope this helps :)

flutter import firebase_core,Auth,database,... but a lot error

Error: Can't use '/C:/src/flutter/.pub-cache/hosted/pub.dartlang.org/firebase_core_platform_interface-4.4.0/lib/src/method_channel/method_channel_firebase.dart' as a part, because it has no 'part of' declaration.
import 'package:firebase_core/firebase_core.dart';
import 'package:flutter/material.dart';
import 'package:firebase_database/firebase_database.dart';
void main() {
runApp(const MaterialApp(
debugShowCheckedModeBanner: false,
home: MyApp(),
));
}
class MyApp extends StatefulWidget {
const MyApp({ Key? key }) : super(key: key);
#override
State<MyApp> createState() => _MyAppState();
}
class _MyAppState extends State<MyApp> {
//final DatabaseReference database = FirebaseDatabase.instance.ref();
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text("Realtime database1234"),
),
);
}
}
enter image description here

No Directionality widget found ; I want to use only Container and Text

I just run the basic flutter code.
I want to make stateful widget, only containing Text("hi")
so I write my code like below
import 'package:flutter/material.dart';
void main() {
runApp(const MyApp());
}
class MyApp extends StatefulWidget {
const MyApp({Key? key}) : super(key: key);
#override
State<MyApp> createState() => _MyAppState();
}
class _MyAppState extends State<MyApp> {
#override
Widget build(BuildContext context) {
return Container(child: Text("hi");
}
}
but I got error
No Directionality widget found.
RichText widgets require a Directionality widget ancestor
I can fix my error to add textDirection attribute,
but I wonder when I use Text I didn't get that error even if I don't use that attribute.
I just want to use only Text, Container
i think its because you dont have MaterialApp
try it like this will work
void main() {
runApp(const MyApp1());
}
class MyApp1 extends StatelessWidget {
const MyApp1({Key? key}) : super(key: key);
#override
Widget build(BuildContext context) {
return MaterialApp(
home: MyApp(),
);
}
}
class MyApp extends StatefulWidget {
const MyApp({Key? key}) : super(key: key);
#override
State<MyApp> createState() => _MyAppState();
}
class _MyAppState extends State<MyApp> {
#override
Widget build(BuildContext context) {
return Container(child: Text("hi"));
}
}
Text needs a Directionality widget to provide information on whether the text is "left-to-right" or "right-to-left". Usually this is done (behind the scene) by MaterialApp widget. If you don't want to use that, you could provide one yourself, and specify the text direction.
Minimal code for a hello world:
import 'package:flutter/material.dart';
void main() {
runApp(
Directionality(
textDirection: TextDirection.ltr,
child: Text("Hello world."),
),
);
}

No constructor 'MaterialApp.' with matching arguments declared in class 'MaterialApp'

I just created a new flutter project and started organized my folders, this is what I have for now:
I'm trying to run it on Windows since I'll use Flutter Desktop for this project, and when I hit run it builds and runs just fine, but when I do a hot-reload the application throws this error message:
No constructor 'MaterialApp.' with matching arguments declared in class 'MaterialApp'.
Receiver: MaterialApp
Tried calling: new MaterialApp.()
Found: new MaterialApp.({Key? key, GlobalKey<NavigatorState>? navigatorKey, GlobalKey<ScaffoldMessengerState>? scaffoldMessengerKey, Widget? home, Map<String, (BuildContext) => Widget> routes, String? initialRoute, ((RouteSettings) => Route<dynamic>?)? onGenerateRoute, ((String) => List<Route<dynamic>>)? onGenerateInitialRoutes, ((RouteSettings) => Route<dynamic>?)? onUnknownRoute, List<NavigatorObserver> navigatorObservers, ((BuildContext, Widget?) => Widget)? builder, String title, ((BuildContext) => String)? onGenerateTitle, Color? color, ThemeData? theme, ThemeData? darkTheme, ThemeData? highContrastTheme, ThemeData? highContrastDarkTheme, ThemeMode? themeMode, Locale? locale, Iterable<LocalizationsDelegate<dynamic>>? localizationsDelegates, ((List<Locale>?, Iterable<Locale>) => Locale?)? localeListResolutionCallback, ((Locale?, Iterable<Locale>) => Locale?)? localeResolutionCallback, Iterable<Locale> supportedLocales, bool debugShowMaterialGrid, bool showPerformanceOverlay, bool checkerboardRasterCacheImages, bool checkerboardOffscreenLayers, bool showSemanticsDebugger, bool debugShowCheckedModeBanner, Map<LogicalKeySet, Intent>? shortcuts, Map<Type, Action<Intent>>? actions, String? restorationScopeId}) => MaterialApp
This is the content of my main.dart:
import 'package:flutter/material.dart';
import 'package:beryllium/src/screens/HomeScreen.dart';
void main() => runApp(MyApp());
class MyApp extends StatefulWidget {
MyApp({Key key}) : super(key: key);
#override
_MyAppState createState() => _MyAppState();
}
class _MyAppState extends State<MyApp> {
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Beryllium',
initialRoute: '/',
routes: {
'/': (contex) => HomeScreen(), //Home screen widget
},
);
}
}
And this the content of the HomeScreen.dart file:
import 'package:flutter/material.dart';
class HomeScreen extends StatefulWidget {
HomeScreen({Key key}) : super(key: key);
#override
_HomeScreenState createState() => _HomeScreenState();
}
class _HomeScreenState extends State<HomeScreen> {
#override
Widget build(BuildContext context) {
return new _HomeScreen();
}
}
class _HomeScreen extends StatelessWidget {
const _HomeScreen({Key key}) : super(key: key);
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('My Book'),
),
body: Center(
child: Container(
child: Text('Home Screen'),
),
));
}
}
If someone has any idea about avoiding this error, please give me a hand.
Thanks in advance.