I have an application where you need to log in to continue (for example with Google).
I would like to redirect the user when the authentification is needed.
However when I run a Navigator.of(context).pushNamed("myroute")
. I got the following error:
══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════ I/flutter ( 5624): The following assertion was thrown building _ModalScopeStatus(active): I/flutter ( 5624): setState() or markNeedsBuild() called during build. I/flutter ( 5624): This Overlay widget cannot be marked as needing to build because the framework is already in the I/flutter ( 5624): process of building widgets. A widget can be marked as needing to be built during the build phase I/flutter ( 5624): only if one of its ancestors is currently building. This exception is allowed because the framework I/flutter ( 5624): builds parent widgets before children, which means a dirty descendant will always be built. I/flutter ( 5624): Otherwise, the framework might not visit this widget during this build phase.
Here is a sample code
void main() { runApp(new MyApp()); } class MyApp extends StatelessWidget { @override Widget build(BuildContext context) { return new MaterialApp( title: 'Flutter Demo', theme: new ThemeData( primarySwatch: Colors.blue, ), home: new MyHomePage(title: 'Flutter Demo Home Page'), routes: <String, WidgetBuilder> { "login" : (BuildContext context) => new LoginPage(), } ); } } class MyHomePage extends StatefulWidget { MyHomePage({Key key, this.title}) : super(key: key); final String title; @override _MyHomePageState createState() => new _MyHomePageState(); } class _MyHomePageState extends State<MyHomePage> { int _counter = 0; @override void initState() { super.initState(); if(!isLoggedIn) { print("not logged in, going to login page"); Navigator.of(context).pushNamed("login"); } } void _incrementCounter() { setState(() { _counter++; }); } void test() { print("hello"); } @override Widget build(BuildContext context) { return new Scaffold( appBar: new AppBar( title: new Text(widget.title), ), body: new Center( child: new Text( 'Button tapped $_counter time${ _counter == 1 ? '' : 's' }.', ), ), floatingActionButton: new FloatingActionButton( onPressed: _incrementCounter, tooltip: 'Increment', child: new Icon(Icons.add), ), // This trailing comma makes auto-formatting nicer for build methods. ); } } class LoginPage extends StatefulWidget { LoginPage({Key key, this.title}) : super(key: key); final String title; @override _LoginPageState createState() => new _LoginPageState(); } class _LoginPageState extends State<LoginPage> { @override Widget build(BuildContext context) { print("building login page"); return new Scaffold( appBar: new AppBar( title: new Text("Sign up / Log In"), ), ), ); } }
I guess I am doing something wrong, maybe aborting a widget build is causing this. However,, how can I achieve this.
Basically : "I go on my page, if not logged, go to Login page"
Thanks, Alexi
initState() is a method that is called once when the Stateful Widget is inserted in the widget tree. We generally override this method if we need to do some sort of initialization work like registering a listener because, unlike build(), this method is called once.
If you are in the same page you want to push, you could do: Navigator. popAndPushNamed(context, C); Which will pop current page (C) and push C.
Try wrapping your Navigator
call:
Navigator.of(context).pushNamed("login");
in a callback that is scheduled with addPostFrameCallback
:
SchedulerBinding.instance.addPostFrameCallback((_) { Navigator.of(context).pushNamed("login"); });
You'll need this import at the top of your file:
import 'package:flutter/scheduler.dart';
As an alternative, consider if you could just have MyHomePage
's build()
method return a LoginPage
instead of a Scaffold
if the user isn't logged in. That will probably interact better with the back button since you don't want the user backing out of the login dialog before they are done logging in.
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