Flutter Navigator.popUntil failed assertion _debugLocked. What's wrong? - flutter

Question

^ ^ ^^ ^ NO! THIS QUESTION DOES NOT HAVE AN ANSWER THERE! ^ ^ ^ ^ ^ ^
I'm having problems with Navigator.popUntil. I wrote a small demo app to show what's happening. Before I post this as a bug, am I using popUntil wrong??
call to popUntil displays
It looks like something is locking up the Navigator (setting _debugLocked) and not releasing it.
main.dart below : (can just be pasted into the Flutter demo app)
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
// This widget is the root of your application.
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MyHomePage(title: 'Routing Test Page'),
onGenerateRoute: (RouteSettings settings) {
switch (settings.name) {
case '/':
return MaterialPageRoute(
builder: (_) => MyHomePage(title: 'Home Page',),
settings: settings,
);
case '/home':
return MaterialPageRoute(
builder: (_) => MyHomePage(title: 'Home Page',),
settings: settings,
);
case '/middlepage':
return MaterialPageRoute(
builder: (_) => MiddlePage(),
settings: settings,
);
case '/bottompage':
return MaterialPageRoute(
builder: (_) => BottomBage(),
settings: settings,
);
default:
return null;
}
},
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text(
'Home Page',
),
OutlineButton(
child: Text('push MiddlePage()'),
onPressed: () => Navigator.push(
context,
MaterialPageRoute(builder: (context) => (MiddlePage())),
),
),
OutlineButton(
child: Text('pushNamed ''/middlepage'''),
onPressed: () => Navigator.pushNamed(context, '/middlepage'),
),
],
),
),
);
}
}
class MiddlePage extends StatelessWidget {
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Middle Page'),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text(
'Middle Page',style: TextStyle(fontWeight: FontWeight.bold)
),
OutlineButton(
child: Text('push BottomPage()'),
onPressed: () => Navigator.push(
context,
MaterialPageRoute(builder: (context) => (BottomBage())),
),
),
OutlineButton(
child: Text('pushNamed ''/bottompage'''),
onPressed: () => Navigator.pushNamed(context, '/bottompage'),
),
OutlineButton(
child: Text('pop'), onPressed: () => Navigator.pop(context)),
OutlineButton(
child: Text('popUntil ''/home'''),
onPressed: () =>
Navigator.popUntil(context, ModalRoute.withName('/home'))),
],
),
),
);
}
}
class BottomBage extends StatelessWidget {
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Bottom page'),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text(
'Bottom Page', style: TextStyle(fontWeight: FontWeight.bold),
),
OutlineButton(
child: Text('push ''home'''),
onPressed: () =>
Navigator.pushNamed(context, '/home'),
),
OutlineButton(
child: Text('pop'),
onPressed: () =>
Navigator.pop(context)),
OutlineButton(
child: Text('popUntil ''/home'''),
onPressed: () =>
Navigator.popUntil(context, ModalRoute.withName('/home')),
),
OutlineButton(
child: Text('popUntil ''/home'' (with Are You Sure box)) '),
onPressed: () async {
try {
if (await _areYouSureDialog(context)) {
Navigator.popUntil(context, ModalRoute.withName('/home'));
}
} catch (e) {
debugPrint("exception: $e");
}
},
),
],
),
),
);
}
}
Future<bool> _areYouSureDialog(BuildContext context) async {
return await showDialog<bool>(
context: context,
builder: (BuildContext context) {
return AlertDialog(
title: const Text('Pop back?'),
content: const Text('Are you sure?'),
actions: <Widget>[
FlatButton(
child: const Text('YES'),
onPressed: () {
Navigator.of(context).pop(true);
},
),
FlatButton(
child: const Text('NO'),
onPressed: () {
Navigator.of(context).pop(false);
},
),
],
);
},
) ??
false;
}

Answer 1

I recreated your case. Whenever we want to pop navigation to the home screen (root) from anywhere, there are couple of ways to do it as below:
1.Using .isFirst method:
Navigator.of(context).popUntil((route) => route.isFirst);
Using defaultRouteName:
Navigator.popUntil(context, ModalRoute.withName(Navigator.defaultRouteName));
By providing the context first, the route will ensure that the navigation will pop to the default always.
You can try with either approach. I tested at my end and it works well.
Hope this answers your question.