Develop Reference

Update data every time a screen is shown on device in Flutter

I have a flutter app with redux state management.
In my app, I want to refetch some data from server when some other data in other screen changed. But in my case, I navigate from screen1 to screen2, and some data chaned in screen 2. I use a boolean flag needUpdate saved to redux and set to true after changes on screen 2.
But when I navigate back to screen1, I need to refetch data if the flag is true. But it did not work and data didnt refetch.
Here is some code:
class FirstScreen extends StatefulWidget {
const FirstScreen({Key? key}) : super(key: key);
#override
State<StatefulWidget> createState() => _FirstScreenState();
}
class _FirstScreenState extends State<FirstScreen> {
#override
void initState() {
super.initState();
}
#override
void didChangeDependencies() async {
final store = StoreProvider.of<AppState>(context);
var needUpdate = store.state.commonState?.needUpdate.value ?? false;
if (needUpdate) {
await store.dispatch(prepareData(context));
}
}
#override
Widget build(BuildContext context) {}
}
class SecondScreen extends StatefulWidget {
const SecondScreen({Key? key}) : super(key: key);
#override
State<SecondScreen> createState() => _SecondScreenState();
}
class _SecondScreenState extends State<SecondScreen> {
#override
void initState() {
super.initState();
}
void onPress() async {
await store.dispatch(ChangeNeedUpdatePortfolio(true));
Navigator.pop(context);
}
#override
Widget build(BuildContext context) {}
}
and Here is my action:
ThunkAction<AppState> updatePortfolioData(BuildContext context) {
return (Store<AppState> store) async {
bool needUpdate = store.state.commonState?.needUpdate.value ?? false;
if (needUpdate) {
...
await store.dispatch(ChangeNeedUpdatePortfolio(false));
...
return;
}
};
}

When I open my flutter app it always shows Sign In screen for few seconds, even if I already signed In in my last session. And after that Main page?

final _navigatorKey = GlobalKey<NavigatorState>();
class MainApp extends StatefulWidget {
const MainApp({Key? key}) : super(key: key);
#override
_MainAppState createState() => _MainAppState();
}
class _MainAppState extends State<MainApp> {
#override
Widget build(BuildContext context) {
return GetMaterialApp(
localizationsDelegates: context.localizationDelegates,
supportedLocales: context.supportedLocales,
locale: context.locale,
navigatorKey: _navigatorKey,
color: Colors.white,
getPages: router.routes,
initialRoute: SignInPageRoute,
routingCallback: (routing) {
final _navigationService = locator<NavigationService>();
final _authService = locator<AuthService>();
if (routing!.current == SignInPageRoute) {
WidgetsBinding.instance!.addPostFrameCallback(
(_) {
bool isLoggedIn = _authService.isLoggedIn();
if (isLoggedIn) {
_navigationService.offAllTo(MainPageRoute);
} else {
return;
}
},
);
}
});
}
}

try with this
bool isLoggedIn = await _authService.isLoggedIn();

showing black screen on backpress Flutter

I am using Webview with WillPopScope, webview internal back button is working fine but on the first page back press is not working.
import 'package:flutter/material.dart';
import 'package:flutter_inappwebview/flutter_inappwebview.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
// This widget is the root of your application.
#override
Widget build(BuildContext context) {
return MaterialApp(
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: SafeArea(child: MyHomePage()),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
InAppWebViewController _controller;
#override
Widget build(BuildContext context) {
return WillPopScope(
onWillPop: () => canGoBack(context),
child: Scaffold(
body: InAppWebView(
initialUrlRequest:
URLRequest(url: Uri.parse("https://www.google.com/")),
onWebViewCreated: onWebviewCreated,
),
),
);
}
void onWebviewCreated(InAppWebViewController controller) {
_controller = controller;
}
canGoBack(BuildContext context) async {
if (await _controller.canGoBack()) {
_controller.goBack();
return Future.value(false);
} else {
return Future.value(true);
}
}
}
tried with
canGoBack(BuildContext context) async {
if (await _controller.canGoBack()) {
_controller.goBack();
return Future.value(false);
} else {
Navigator.pop(context, true);
return Future.value(false);
}
}
the issue is showing the black if there is no webview history.

You don't have any previous root and you're using
Navigator.pop(context, true); // in canGoBack function
That's cause to issue. Remove that line and it will work.

how can progress-bar listen value changes using flutter provider and update another widget?

**this is my provider **
MultiProvider(
child: MyApp(),
providers: [
ChangeNotifierProvider(create: (BuildContext context)=> Downloads(),),)]
***this class implements notifylistner when i print out _progress it all works properly
but the ui wiget does not rebuid to give out the outputs ***
class Downloads extends ChangeNotifier {
int _progress= 0;
int get progress => _progress;
void setProgress(int p) {
_progress = p;
notifyListeners();
}
}
i have removed progress-bar widget to make it simple instead show output value
class FileDownload extends StatelessWidget {
const FileDownload({Key key}) : super(key: key);
#override
Widget build(BuildContext context) {
return Scaffold(body: progessUi());
}
}
class progessUi extends StatelessWidget {
const progessUi({Key key}) : super(key: key);
#override
Widget build(BuildContext context) {
final model = Provider.of<Downloads>(context);
return Container(child: Text(model.progress.toString()));
}
}
*this just a snippet where the calls to the Download function are made *
if (message['event'] == EV_PROGRESS) {
Downloads().setProgress(message['progress']);
}
if (message['event'] == EV_DONE) {
Downloads().setProgress(100);
}

Flutter: How to pass variables from StatelessWidget to StatefulWidget

The problem is that I cannot pass the values of my own class ForceSelection values from another screen to another screen's StatefulWidget. It works fine in StatelessWidget. I have tried to learn from this flutter tutorial: https://flutter.dev/docs/cookbook/navigation/passing-data#4-navigate-and-pass-data-to-the-detail-screen
I have this kind of class in levelSelection.dart
class ForceSelection {
final String forceSelection;
final String langSelection;
ForceSelection(this.forceSelection, this.langSelection);
}
I am trying to pass the values to next file PlayQuiz.dart
Game(forceSelection: ForceSelection('maa', 'fin'))
game.dart looks like this:
class Game extends StatelessWidget {
final ForceSelection forceSelection;
Game({Key key, #required this.forceSelection}) : super(key: key);
#override
Widget build(BuildContext context) {
return MaterialApp(
title: forceSelection.langSelection, // TODO should work and change later
theme: new ThemeData(
primaryColor: Colors.white,
),
home: PlayQuiz(),
);
}
}
And I want to pass the ForceSelection values to PlayQuiz()
class PlayQuizState extends State<PlayQuiz> {
Game.forceSelection // <--- How can I get the value out of here?
}
class PlayQuiz extends StatefulWidget {
#override
PlayQuizState createState() => new PlayQuizState();
}
The whole code can be found here: https://pastebin.com/nKssz42R
and also levelSelection.dart: https://pastebin.com/8QbBD0A2

Try this code
Added forceSelecton argument in PlayQuiz()
class Game extends StatelessWidget {
final ForceSelection forceSelection;
Game({Key key, #required this.forceSelection}) : super(key: key);
#override
Widget build(BuildContext context) {
return MaterialApp(
title: forceSelection.langSelection, // TODO should work and change later
theme: new ThemeData(
primaryColor: Colors.white,
),
home: PlayQuiz(forceSelection),
);
}
}
In Play Quiz
class PlayQuiz extends StatefulWidget {
final ForceSelection forceSelection;
PlayQuiz(this.forceSelection);
#override
PlayQuizState createState() => new PlayQuizState(forceSelection);
}
In PlayQuizState
class PlayQuizState extends State<PlayQuiz> {
ForceSelection forceSelection;
PlayQuizState(ForceSelection forceSelection) {
this.forceSelection = forceSelection;
}
}