showDialog from root widget - flutter

Question

I want to show a dialog from root widget (the one that created MaterialApp) I have a NavigatorState instance, but showDialog requires context that would return Navigator.of(context).
It looks like I need to provide context from a route, but I can't do this, because the root widget does not have it.
EDIT: I have found a workaround: I can push fake route that is only there to showDialog and then pop that route when dialog finishes. Not pretty but works.

Answer 1

I fixed the problem by using navigatorKey.currentState.overlay.context. Here is example:
class GlobalDialogApp extends StatefulWidget {
#override
_GlobalDialogAppState createState() => _GlobalDialogAppState();
}
class _GlobalDialogAppState extends State<GlobalDialogApp> {
final navigatorKey = GlobalKey<NavigatorState>();
void show() {
final context = navigatorKey.currentState.overlay.context;
final dialog = AlertDialog(
content: Text('Test'),
);
showDialog(context: context, builder: (x) => dialog);
}
#override
Widget build(BuildContext context) {
return MaterialApp(
navigatorKey: navigatorKey,
home: Scaffold(
body: Center(
child: RaisedButton(
child: Text('Show alert'),
onPressed: show,
),
),
),
);
}
}

Answer 2

tl;dr: If you want to call showDialog from your root widget, extrude your code into another widget (e.g. a StatelessWidget), and call showDialog there.
Anyway, in the following I'm going to assume you are running into this issue:
flutter: No MaterialLocalizations found.
flutter: MyApp widgets require MaterialLocalizations to be provided by a Localizations widget ancestor.
flutter: Localizations are used to generate many different messages, labels,and abbreviations which are used by the material library.
As said before, showDialog can only be called in a BuildContext whose ancestor has a MaterialApp. Therefore you can't directly call showDialogif you have a structure like this:
- MaterialApp
- Scaffold
- Button // call show Dialog here
In a code example this would result in code like this, throwing the error given above:
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
theme: ThemeData(),
home: Scaffold(
body: Center(
child: RaisedButton(
child: Text('Show dialog!'),
onPressed: () {
showDialog(
context: context,
builder: (BuildContext context) {
return Dialog(
child: Text('Dialog.'),
);
});
}),
),
),
);
}
}
To solve this error from occuring you can create a new Widget, which has its own BuildContext. The modified structure would look like this:
- MaterialApp
- Home
- Home // your own (Stateless)Widget
- Button // call show Dialog here
Modifying the code example to the structure given above, results in the code snippet below. showDialogcan be called without throwing the error.
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
theme: ThemeData(),
home: Home()
);
}
}
class Home extends StatelessWidget {
#override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: RaisedButton(
child: Text('Show dialog!'),
onPressed: () {
showDialog(
context: context,
builder: (BuildContext context) {
return Dialog(
child: Text('Dialog.'),
);
});
}),
),
);
}
}

Answer 3

They changed the way the navigator overlay works.
This is the working solution for us as the accepted one isn't anymore.
// If you want to use the context for anything.
final context = navigatorKey.currentState.overlay.context;
// How to insert the dialog into the display queue.
navigatorKey.currentState.overlay.insert(anyDialog);

Answer 4

If you already have a context object, you can get root material app's context by
final rootContext = context.findRootAncestorStateOfType<NavigatorState>().context
and passing this to showDialog or showModalBottomSheet context argument.

Answer 5

Since showDialog is used for showing a material dialog It can be used for showing dialogs inside a MaterialApp widget only. It can not be used to show dialog outside it.

Answer 6

If it helps anyone else, inject the navigator key into a dialog widget like so.
class MyApp extends StatelessWidget {
MyApp({Key key});
final navigatorKey = GlobalKey<NavigatorState>();
#override
Widget build(BuildContext context) {
return MaterialApp(
navigatorKey: navigatorKey,
onGenerateRoute: Router.generateRoute,
// ...
builder: (context, routeChild) {
return Material(
child: InviteRequestModal(
navigatorKey: navigatorKey,
child: routeChild,
),
);
},
);
}
Then in the Widget that requires the modal, you can use it as mentioned above.
class InviteRequestModal extends StatelessWidget {
final Widget child;
final GlobalKey<NavigatorState> navigatorKey;
InviteRequestModal({
Key key,
this.child,
this.navigatorKey,
}) : super(key: key);
void _showInviteRequest(InviteRequest invite) {
final context = navigatorKey.currentState.overlay.context;
showDialog(
context: context,
builder: (_) {
// Your dialog content
return Container();
}
);
}
#override
Widget build(BuildContext context) {
return BlocListener<InviteContactsBloc, InviteContactsState>(
listenWhen: (previous, current) => current is InviteRequestLoaded,
listener: (_, state) {
if (state is InviteRequestLoaded) {
_showInviteRequest(state.invite);
}
},
child: child,
);
}
}

Answer 7

The answer just that simple, when you are providing MaterialApp to the tree it was providing but at the immediate bottom you are the context which obtained before providing MaterialApp to the tree. To resolve the issue you need to create a new context which will have the MaterialApp properties. For that wrap a Builder above the home and vola it is working...!
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: Builder(builder: (context) {
return HomePage(
child: Center(
child: TextButton(
onPressed: () async {
await showDialog(
context: context,
builder: (context) => Dialog(
child: Container(
color: Colors.green,
height: 50,
width: 100,
child: Text("Hi, I am a dialog"),
),
),
);
},
child: Text("Tap me"),
),
),
);
}),
);
}

Answer 8

For those wanting to see how to do this in a multiple widget/route/file scenario, I used it with InheritedWidget and an extension on BuildContext.
main.dart
import 'package:flutter/material.dart';
import 'package:myapp/home_screen.dart';
import 'package:myapp/app_navkey.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
final navigatorKey = GlobalKey<NavigatorState>();
#override
Widget build(BuildContext context) {
return AppNavKey(
navigatorKey: navigatorKey,
child: MaterialApp(
navigatorKey: navigatorKey,
theme: ThemeData(),
home: Scaffold(
body: HomeScreen(),
),
),
);
}
}
home_screen.dart
import 'package:myapp/extensions.dart';
class HomeScreen extends StatelessWidget {
#override
Widget build(BuildContext context) {
final overlayContext = context.navigationKey().currentState.overlay.context;
return Center(
child: TextButton(
child: Text('Show dialog!'),
onPressed: () {
showDialog(
context: overlayContext, // use app level navigation context overlay
builder: (BuildContext context) {
return Dialog(
child: Text('Dialog.'),
);
});
},
),
);
}
}
app_navkey.dart
import 'package:flutter/widgets.dart';
class AppNavKey extends InheritedWidget {
final Widget child;
final GlobalKey<NavigatorState> navigatorKey;
AppNavKey({
Key key,
#required this.child,
#required this.navigatorKey,
}) : super(key: key, child: child);
static GlobalKey<NavigatorState> of(BuildContext context) {
final ctx = context.dependOnInheritedWidgetOfExactType<AppNavKey>();
if (ctx == null) throw Exception('Could not find ancestor of type AppNavProvider');
return ctx.navigatorKey;
}
#override
bool updateShouldNotify(covariant InheritedWidget oldWidget) => false;
}
extensions.dart
import 'package:flutter/widgets.dart';
import 'package:myapp/app_navkey.dart';
extension SwitchTabContext on BuildContext {
/// Get app level NavigatorState key.
/// ```dart
/// context.navigationKey();
/// ```
GlobalKey<NavigatorState> navigationKey() => AppNavKey.of(this);
}