So, I'm trying out the BLOCK pattern recently and after having imported the block_pattern package in my pubsec yaml file like this
dependencies:
flutter:
sdk: flutter
# The following adds the Cupertino Icons font to your application.
# Use with the CupertinoIcons class for iOS style icons.
cupertino_icons: ^0.1.2
bloc_pattern: ^2.2.2+3
rxdart:
Now, I have establish a class called CartListBloc as an extend of BlockBase
class CartListBloc extends BlocBase {
CartListBloc();
//etc...
When I try to put a BlockProvider in the main class it isn't recognized by the IDE despite having the correct imports.
import 'package:bloc_pattern/bloc_pattern.dart';
import 'bloc/cartListBloc.dart';
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return BlockProvider( // here it doesn't recognize BlockProvider
blocs: [
],
child:
);
}
}
You have to get rid of the k in BlocProvider
import 'package:bloc_pattern/bloc_pattern.dart';
import 'bloc/cartListBloc.dart';
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return BlocProvider( // remove the K
blocs: [
],
child:
);
}
}
Related
A flutter newbie, I'm trying to get my app to take values from a local json file and render them on-screen.
The logic isn't waiting for the class constructor to populate the relevant string variable before rendering the app on screen.
Here's the code that illustrates my problem.
First, my main.dart file:
import 'dart:io';
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'sampleDataClass.dart';
import 'package:provider/provider.dart';
String assetFilePath = 'assets/basicData.json';
void main() async {
WidgetsFlutterBinding.ensureInitialized();
FlutterError.onError = (details) {
FlutterError.presentError(details);
if (kReleaseMode) exit(1);
};
runApp(const MyApp());
}
class MyApp extends StatefulWidget {
const MyApp({super.key});
#override
State<MyApp> createState() => _MyAppState();
}
class _MyAppState extends State<MyApp> {
#override
Widget build(BuildContext context) {
return ChangeNotifierProvider(
create: (context) => MyAppState(),
child: const MaterialApp(
title: "Sample screen",
home: MyHomePage(),
)
);
}
}
class MyAppState extends ChangeNotifier {
SampleDataClass current = SampleDataClass(assetFilePath);
}
class MyHomePage extends StatelessWidget {
const MyHomePage({super.key});
#override
Widget build(BuildContext context) {
var myAppState = context.watch<MyAppState>();
var myAppBasicData = myAppState.current;
return Scaffold(
appBar: AppBar(
backgroundColor: Colors.indigo,
foregroundColor: Colors.amberAccent,
title: const Text("This is the App Bar"),
elevation: 10,
),
body: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: [
Row(children: [
Expanded(
child: Container(
color: Colors.blueGrey,
padding: const EdgeInsets.all(10),
child: (
Text(myAppBasicData.language,
style: const TextStyle(
color: Colors.white,
))))),
]),
]
),
);
}
}
Here is my SampleDataClass.dart file:
import 'dart:core';
import 'dart:convert';
import 'package:flutter/services.dart' show rootBundle;
class SampleDataClass {
String classFilePath = "";
String language = "not populated";
String batteryName = "not populated";
SampleDataClass(filePath) {
rootBundle.loadString(filePath).then((jsonDataString) {
Map classDataMap = jsonDecode(jsonDataString);
language = classDataMap['language'];
print(language);
batteryName = classDataMap['batteryName'];
print(batteryName);
});
}
Map<String, dynamic> toJson() => {
'language': language,
'batteryName': batteryName,
};
}
And here's my pubspec.yaml file:
name: samples
description: A new Flutter project.
environment:
sdk: '>=2.18.6 <3.0.0'
flutter:
sdk: flutter
cupertino_icons: ^1.0.2
provider: ^4.1.1
dev_dependencies:
flutter_test:
sdk: flutter
flutter_lints: ^2.0.0
flutter:
uses-material-design: true
assets:
- assets/basicData.json
Finally, my basicData.json file looks like this:
{
"language": "English",
"batteryName": "Exercise 32"
}
The print statements in the sampleDataClass class work fine but as you can see if you run the code (from the command line using "flutter run --no-sound-null-safety"), the app renders the initial values of the variables before the class constructor assigns the json values to them.
What I expected was the class constructor to complete writing the relevant json values to the class members before handing back the class instance to the build widget in main.dart to render the app on-screen.
I realise that this is a very elementary question, but it is a key pending learning task for me!
Thank you all very much in advance!
it looks like rootBundle is an async function, you have to wait till it finishes then you notify the UI to render with new data,
How to handle this :
you should have 3 states loading state , error state , loaded state ,
create an init(path) function in SampleDataClass class that returns SampleDataClass instance.
Also, in the init() function at the beginning you have to change the state to loading state then when you get the data you set the state to loaded state, then notify listeners this will help the screen to know which state the page is in.
in the screen , call didChangeDependencies() and inside it, call your Provider => init function ( current = contecxt.read<YPUR_PROVIDER>().init(path); )
therefore the current object is being initialized, the page is showing a loader, and once the initialization is done, the provider will notify the page and it will change the loading view to the loaded view (your current view).
Another Tip::
your app will close whenever there is an error, it is not a good practice, since flutter will through non-fatal exception
FlutterError.onError = (details) {
FlutterError.presentError(details);
if (kReleaseMode) exit(1);
There is a choice of two excellent solutions to my problem with very little effort and no need for any change management (yet).
Indeed, so similar is the problem described that I probably should have found it before I posted this query here. As a newbie in this discipline, I clearly didn't conduct my search with the appropriate key words; for that I apologise!
Thanks very much to everyone for your patience.
The two solution options (which even I was able to follow) can be found here:
Calling an async method from a constructor in Dart
My code is very simple:
import 'package:flutter/material.dart';
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(title:"title", home: Scaffold(body: TextField()));
}
}
void main() {
runApp(MyApp());
}
No matter how I try to include the text field, the program just crushes.
I'm compiling to web, maybe that's related to the problem?
Edit: So that's awkward. But the code seems to work perfectly fine now...
Though the following code still crashes after adding the text field:
import 'package:flutter/material.dart';
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(title:"title", home: Scaffold(body:
Row(children: [
Column(children: [
TextField()
])
]
)));
}
}
void main() {
runApp(MyApp());
}
This happens, because there is no width constraint to the TextField.
In your case, wrapping the column in an Expanded widget should fix the problem.
See the flutter documentation for more info and solutions to this problem: https://flutter.dev/docs/testing/common-errors#an-inputdecoratorcannot-have-an-unbounded-width
how can I make my own flutter widget / flutter class deprecated (so that when I or anyone else uses the class as a widget that there is a deprecated annotation)?
Here's my current code: https://gist.github.com/janhecker/538a8f0610a29e6be6c7fbce1f525d39
Just add this on top of your widget:
#Deprecated('Use this other widget instead')
class MyWidget extends StatelessWidget { ... }
I'm using the auto_route package in order to route my app and until 2 days ago everything worked just fine, until now.
For some reason, I'm getting the following error.
SYSTEM:
flutter: 1.22
dart: 2.10.0
auto_route: ^0.6.7
ERROR:
../../.pub-cache/hosted/pub.dartlang.org/custom_navigator-0.3.0/lib/custom_navigator.dart:60:7: Error: The non-abstract class '_CustomNavigatorState' is missing implementations for these members:
- WidgetsBindingObserver.didPushRouteInformation
Try to either
- provide an implementation,
- inherit an implementation from a superclass or mixin,
- mark the class as abstract, or
- provide a 'noSuchMethod' implementation.
class _CustomNavigatorState extends State<CustomNavigator>
^^^^^^^^^^^^^^^^^^^^^
/opt/flutter/packages/flutter/lib/src/widgets/binding.dart:122:16: Context: 'WidgetsBindingObserver.didPushRouteInformation' is defined here.
Future<bool> didPushRouteInformation(RouteInformation routeInformation) {
main.dart
import 'package:device_simulator/device_simulator.dart';
import 'package:flutter/material.dart';
import 'package:auto_route/auto_route.dart';
import 'Test.gr.dart' as r;
void main() => runApp(MyApp());
const bool debugEnableDeviceSimulator = true;
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
builder: ExtendedNavigator.builder<r.Router>(
router: r.Router(),
builder: (context, extendedNav) => DeviceSimulator(
enable: debugEnableDeviceSimulator,
child:
Scaffold(body: extendedNav, backgroundColor: Colors.red ),
),
),
);
}
}
Also, I should mention, because of some update of flutter I guess, now I need to use r.Router instead of just Router.
Test.dart
import 'package:auto_route/auto_route_annotations.dart';
#MaterialAutoRouter(
routes: <AutoRoute>[],
)
class $Router {}
And also if has any importance here it's the generated file
Test.gr.dart
// GENERATED CODE - DO NOT MODIFY BY HAND
// **************************************************************************
// AutoRouteGenerator
// **************************************************************************
// ignore_for_file: public_member_api_docs
import 'package:auto_route/auto_route.dart';
class Routes {
static const all = <String>{};
}
class Router extends RouterBase {
#override
List<RouteDef> get routes => _routes;
final _routes = <RouteDef>[];
#override
Map<Type, AutoRouteFactory> get pagesMap => _pagesMap;
final _pagesMap = <Type, AutoRouteFactory>{};
}
Do you have any idea what's going one here or how can I fix this? Or if I can't fix this, what can I use instead of the auto_route package which will offer me the same benefice?
i solved this problem with add some function on library CustomNavigator :
Future<bool> didPushRouteInformation(RouteInformation routeInformation) {
return didPushRoute(routeInformation.location);
}
Find the place where the error is generating. Add the following function below there. I did the same and my problem is solved.
Future<bool> didPushRouteInformation(RouteInformation routeInformation) {
return didPushRoute(routeInformation.location);
}
So I'm new to flutter and dart.I've made multiple android apps and I am pretty familiar with coding but I just can't get to know flutter. I use Android Studio as Ide and when I try to compile my code , on the assembleDebug part, This error is thrown:
c:\b\s\w\ir\k\src\third_party\dart\runtime\vm\zone.cc: 54: error: Out
of memory.
version=2.4.0 (Wed Jun 19 11:53:45 2019 +0200) on "windows_x64"
thread=1336, isolate=main(0000029506C2CDE0)
pc 0x00007ff7b33d2b1b fp 0x000000d10cbfb0a0 Unknown symbol
-- End of DumpStackTrace
For now, I haven't done anything to fix the problem because I don't know why
main.dart
import 'package:flutter/material.dart';
import 'constants.dart';
import 'package:flutter_svg/flutter_svg.dart';
void main() {
runApp(UnitConverterApp());
}
//on create
class UnitConverterApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
debugShowCheckedModeBanner: false,
title: 'Distivity Todolist',
theme: Constants.getTheme(),
home: CategoryRoute(),
);
}
}
class CategoryRoute extends StatefulWidget {
const CategoryRoute();
#override
_CategoryRouteState createState() => _CategoryRouteState();
}
class _CategoryRouteState extends State<CategoryRoute> {
/// Function to call when a [Category] is tapped.
void _onCategoryTap() {
setState(() {
});
}
#override
Widget build(BuildContext context) {
return Center(
child: InkWell(
onTap: () => _onCategoryTap(),
child: SvgPicture.asset(
Constants.add,
semanticsLabel: 'ad'
),
)
);
}
}
constants.dart
import 'package:flutter/material.dart';
class Constants{
static ThemeData getTheme(){
return ThemeData(
primaryColor: colorSwatch,
);
}
static const primaryColor = 0xff4FB484;
static ColorSwatch colorSwatch = ColorSwatch(primaryColor, const<String,Color>{
"primary_color": Color(primaryColor),
"primary_dark":Color(0xff306D50),
"black_16": Color(0xff161616),
"black_20":Color(0xff202020),
"the_blackest":Color(0xff000000),
"color_white":Color(0xffF7F7F7),
"the_whitest":Color(0xffffffff)
});
static const String add = 'assets/add.svg';
}
pubspec.yaml
name: distivity_todolist
description: A new Flutter application.
https://developer.apple.com/library/archive/documentation/General/Reference/InfoPlistKeyReference/Articles/CoreFoundationKeys.html
version: 1.0.0+1
environment:
sdk: ">=2.1.0 <3.0.0"
dependencies:
flutter:
sdk: flutter
cupertino_icons: ^0.1.2
dev_dependencies:
flutter_svg: 0.13.1
flutter_test:
sdk: flutter
flutter:
uses-material-design: true
assets:
- assets/add.svg