Getting exception when trying to open a new page with Navigator - flutter

Question

I have a push notification manager class that is singleton where I listen for notifications from Firebase FCM and I handle them based on the logic and open specific screens.
I init with BuildContext that PushtNotificatonManager class inside HomePage that iS called from main.dart.
class HomePage extends StatefulWidget {
const HomePage({Key? key}) : super(key: key);
#override
State<HomePage> createState() => _HomePageState();
}
class _HomePageState extends State<HomePage> {
#override
void initState() {
super.initState();
PushNotificationsManager().listen(context);
}
This is code from main.dart
Future<void> backgroundHandler(RemoteMessage message) async {
print('Handling a background message ${message.messageId}');
print('Content of message: ' + message.toString());
}
Future<void> main() async {
WidgetsFlutterBinding.ensureInitialized();
configureInjections();
await Firebase.initializeApp(
options: DefaultFirebaseOptions.currentPlatform,
);
FirebaseMessaging.onBackgroundMessage(backgroundHandler);
runApp(SayApp());
}
This is part of the code from PushNotificationsManager class
#injectable
class PushNotificationsManager {
static final PushNotificationsManager _instance = PushNotificationsManager._internal();
factory PushNotificationsManager() {
return _instance;
}
PushNotificationsManager._internal();
Future<void> listen(BuildContext context) async {
if (Platform.isIOS) {
NotificationSettings settings = await FirebaseMessaging.instance.requestPermission(
alert: true,
badge: true,
provisional: false,
sound: true,
);
if (settings.authorizationStatus == AuthorizationStatus.authorized) {
print('User granted permission');
await _handleNotifications(context);
}
} else {
await _handleNotifications(context);
}
}
Future<void> _handleNotifications(BuildContext context) async {
// gives the message on which user taps and it opened the app from terminated state
FirebaseMessaging.instance.getInitialMessage().then((message) {
if (message != null) {
openNotification(message, context);
}
});
// foreground
FirebaseMessaging.onMessage.listen((message) {
if (message.notification != null) {
_showInAppNotification(message);
}
});
// When the app is in background but opened and user taps on the notification
FirebaseMessaging.onMessageOpenedApp.listen((message) {
openNotification(message, context);
});
}
Inside showInAppNotifications I am trying to display notifications as pop up and when the user clicks on it, I try to open a specific screen.
void _displayInAppNotifications(RemoteMessage message) {
FlutterRingtonePlayer.playNotification();
showOverlayNotification((context) {
return GestureDetector(
onTap: () {
openNotification(message, context);
OverlaySupportEntry.of(context)!.dismiss();
},
child: SafeArea(
child: Card(
child: ListTile(
leading: message.data[NotificationType.NOTIFICATION_TYPE] ==
NotificationType.PRIVATE_MESSAGE_1_ON_1
? Avatar(text: message.notification!.title!)
: SizedBox.fromSize(
size: const Size(40, 40),
child: ClipOval(
child: Container(
child: SvgPicture.asset(SvgIcons.sayAppWaveLogo),
))),
title:
Text(message.notification!.title!, overflow: TextOverflow.ellipsis, maxLines: 1),
subtitle: Text(
message.notification!.body!,
overflow: TextOverflow.ellipsis,
maxLines: 2,
),
trailing: IconButton(
icon: Icon(Icons.close),
onPressed: () {
OverlaySupportEntry.of(context)!.dismiss();
}),
),
),
),
);
}, duration: Duration(seconds: 4), position: NotificationPosition.top);
}
I have this method navigateToChannelDetailsPage that is called from the above method and here I am getting an exception.
Future<void> navigateToChannelDetailsPage(ChannelEntity channel, BuildContext context) async {
var cubit = BlocProvider.of<HomeCubit>(context);
var isUserChannelMember = await cubit.isCurrentUserChannelMember(channel);
if (!isUserChannelMember) return;
var isUserMutedPublic = await cubit.getIsUserMutedPublic(channel);
if (isUserMutedPublic) channel.isUserMutedPublic = isUserMutedPublic;
return PageNavigator.navigate(
context, ChannelDetailsPage(channel: channel, isFromAdminNotification: true))
.then((_) {
FocusManager.instance.primaryFocus?.unfocus();
cubit.updateChannelMemberChatDetailsDataOnChannelClosed(channel);
});
}
This is the exception:
E/flutter (25412): [ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: Looking up a deactivated widget's ancestor is unsafe.
E/flutter (25412): At this point the state of the widget's element tree is no longer stable.
E/flutter (25412): To safely refer to a widget's ancestor in its dispose() method, save a reference to the ancestor by calling dependOnInheritedWidgetOfExactType() in the widget's didChangeDependencies() method.
E/flutter (25412): #0 Element._debugCheckStateIsActiveForAncestorLookup.<anonymous closure> (package:flutter/src/widgets/framework.dart:4241:9)
E/flutter (25412): #1 Element._debugCheckStateIsActiveForAncestorLookup (package:flutter/src/widgets/framework.dart:4255:6)
E/flutter (25412): #2 Element.getElementForInheritedWidgetOfExactType (package:flutter/src/widgets/framework.dart:4286:12)
E/flutter (25412): #3 Provider._inheritedElementOf (package:provider/src/provider.dart:339:38)
E/flutter (25412): #4 Provider.of (package:provider/src/provider.dart:293:30)
E/flutter (25412): #5 BlocProvider.of (package:flutter_bloc/src/bloc_provider.dart:100:23)
E/flutter (25412): #6 PushNotificationsManager.navigateToChannelDetailsPage (package:say_app/presentation/notification/push_notifications_manager.dart:204:30)
E/flutter (25412): #7 PushNotificationsManager.openNotification (package:say_app/presentation/notification/push_notifications_manager.dart:180:9)
E/flutter (25412): <asynchronous suspension>
Any ideas?

Answer 1

You get that error because, by the time you wait for some things to finish the execution, you do something else on the app (go back one or few screens let's say) so your widget/screen gets disposed of and is no longer in the widget tree when you call PageNavigator.navigate(context, ...).
So to prevent that from happening, you can use the mounted flag to check if your StatefulWidget is still active, like:
if(mounted) PageNavigator.navigate(context, ...)
But in that case, the page will not get pushed if the widget is disposed of. So if you still want to push the new screen, no matter what happens in the meantime (even if that widget gets disposed of), you can have your global navigatorKey which you assign to the MaterialApp key property and use the context from navigatorKey while navigating, since it should always be usable (i.e. the MaterialApp should always be present in the widget tree). Solution example:
import 'package:flutter/material.dart';
final GlobalKey<NavigatorState> navigatorKey = GlobalKey<NavigatorState>();
void main() {
runApp(const MyApp());
}
class MyApp extends StatelessWidget {
const MyApp({super.key});
#override
Widget build(BuildContext context) {
return MaterialApp(
navigatorKey: navigatorKey,
home: const HomePage(),
);
}
}
So now you navigate like:
PageNavigator.navigate(navigatorKey.currentContext!, ...) // your use case
Navigator.of(navigatorKey.currentContext!).push(...) // the usual way using global navigatorKey