markNeedsBuild fails assertion with conditional Drawer #42580
Description
I have a Drawer that is only enabled on the root page, using this code:
drawer: Navigator.of(context).canPop() ? null : Drawer(child: SettingsDrawer()),When I modify a "dark mode" setting in the drawer that causes a rebuild, I get the following error:
════════ Exception caught by widgets library ═══════════════════════════════════
The following assertion was thrown while finalizing the widget tree:
setState() or markNeedsBuild() called when widget tree was locked.
This Scaffold widget cannot be marked as needing to build because the framework is locked.
The widget on which setState() or markNeedsBuild() was called was: Scaffold
dependencies: [_InheritedTheme, MediaQuery, _LocalizationsScope-[GlobalKey#a243d], Directionality]
state: ScaffoldState#e99f6(tickers: tracking 2 tickers)
When the exception was thrown, this was the stack
#0 Element.markNeedsBuild.<anonymous closure>
package:flutter/…/widgets/framework.dart:3692
#1 Element.markNeedsBuild
package:flutter/…/widgets/framework.dart:3702
#2 State.setState
package:flutter/…/widgets/framework.dart:1161
#3 ScaffoldState._drawerOpenedCallback
package:flutter/…/material/scaffold.dart:1399
#4 DrawerControllerState.close
package:flutter/…/material/drawer.dart:405
...
════════════════════════════════════════════════════════════════════════════════
════════ Exception caught by animation library ═════════════════════════════════
'package:flutter/src/widgets/framework.dart': Failed assertion: line 3658 pos 12: '_debugLifecycleState != _ElementLifecycle.defunct': is not true.
════════════════════════════════════════════════════════════════════════════════
In order to reproduce the issue, open the Drawer and tap the Dark Mode switch with the following (simplified) sample app:
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
void main() => runApp(AppConfig());
class Prefs extends ChangeNotifier {
bool _darkMode = false;
bool get darkMode => _darkMode;
set darkMode(bool newValue) {
if (newValue == _darkMode) return;
_darkMode = newValue;
notifyListeners();
}
}
class AppConfig extends StatefulWidget {
_AppConfigState createState() => _AppConfigState();
}
class _AppConfigState extends State<AppConfig> {
final Prefs prefs = Prefs();
@override
Widget build(BuildContext context) {
return ChangeNotifierProvider<Prefs>.value(value: prefs, child: MyApp());
}
}
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
final prefs = Provider.of<Prefs>(context);
return MaterialApp(
title: 'Test',
theme: ThemeData(brightness: prefs.darkMode ? Brightness.dark : Brightness.light, primarySwatch: Colors.blue),
home: Home(),
);
}
}
class Home extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: Text("test")),
drawer: Navigator.of(context).canPop() ? null : Drawer(child: SettingsDrawer()),
body: Container(),
);
}
}
class SettingsDrawer extends StatelessWidget {
@override
Widget build(BuildContext context) {
final prefs = Provider.of<Prefs>(context);
return Scaffold(
body: ListView(
padding: EdgeInsets.zero,
children: <Widget>[
DrawerHeader(
child: Text('Settings'),
decoration: BoxDecoration(
color: Colors.blue,
),
),
ListTile(
leading: Text("Dark Mode"),
title: Switch(
value: prefs.darkMode,
onChanged: (value) => prefs.darkMode = value,
),
),
],
),
);
}
}