I am currently trying to learn Navigation 2.0 in conjunction with BLoC.
I've followed the raywenderlich's guide [1] successfully (it's a bit outdated) and i tried to move forward managing the state with BLoC (this guide uses Provider) and when i did it successfully, i tried to take a step further and i tried to follow JalalOkbi's guide [2] because of a more advanced abstraction level provided. The third link [3] is the github repo with the full (now failing) project.
But after 5 days of trying i stumbled in several errors and i can't figure this out: i am currently facing this error:
I/flutter (10212): looking for /
I/flutter (10212): found Splash("null", null, null)
I/flutter (10212): looking for /
I/flutter (10212): found Splash("null", null, null)
════════ Exception caught by widgets library ═══════════════════════════════════
The following assertion was thrown building Builder:
The settings getter of a page-based Route must return a Page object. Please set the settings to the Page in the Page.createRoute method.
'package:flutter/src/widgets/navigator.dart':
package:flutter/…/widgets/navigator.dart:1
Failed assertion: line 3361 pos 9: 'entry.route.settings == page'
════════ Exception caught by widgets library ═══════════════════════════════════
A GlobalKey was used multiple times inside one widget's child list.
The relevant error-causing widget was
MaterialApp
lib\main.dart:40
════════════════════════════════════════════════════════════════════════════════
[1] https://www.raywenderlich.com/19457817-flutter-navigator-2-0-and-deep-links
[2] https://medium.com/#JalalOkbi/flutter-navigator-2-0-with-bloc-the-ultimate-guide-6672b115adf
[3] https://github.com/msimoncini90/flutter_navigation_2.0
If your page object is defined like
class SplashPage extends Page {
#override
Route createRoute(BuildContext context) {
return MaterialPageRoute(
builder: (BuildContext context) => const SplashScreen(),
);
}
}
The issue is that there is a missing setting in the page definition, which is what the error is showing. The correct code looks like
class SplashPage extends Page {
#override
Route createRoute(BuildContext context) {
return MaterialPageRoute(
settings: this,
builder: (BuildContext context) => const SplashScreen(),
);
}
}
Notice that the settings: this parameter, which solves what the error is describing.
Related
This following was the error show in the app interface,
Error: Could not find the correct Provider above this MainScreen Widget
This happens because you used a BuildContext that does not include the provider
of your choice. There are a few common scenarios:
-You added a new provider in your main.dart and performed a hot-reload.
To fix, perform a hot-restart.
-The provider you are trying to read is in a different route.
Providers are "scoped". So if you insert of provider inside a route, then other routes will not be able to access that provider.
-You used a BuildContext that is an ancestor of the provider you are trying to read.
Make sure that MainScreen is under your MultiProvider/Provider. This usually happens when you are creating a provider and trying to read it immediately.
For example, instead of:
Widget build(BuildContext context) {
return Provider(
create: () => Example().
// Will throw a ProviderNotFoundError, because context is associated
// to the widget that is the parent of Provider child: Text(context.watch()), ), } consider using builderlike so: Widget build(BuildContext context) { } return Provider( ), create: () => Example(). // we usebuilderto obtain a newBuildContext` that has access to the provider builder: (context) {
}
// No longer throws
return Text(context.watch()).
If none of these solutions work, consider asking for help on StackOverflow:
https://stackoverflow.com/questions/tagged/flutter
See also: https://flutter.dev/docs/testing/errors
I have used persistent_bottom_nav_bar 5.0.2 package and from the first tab page which is homepage I navigate to further some pages and than finally I use the following navigator to come back to this page on same tab
Navigator.of(context).pushAndRemoveUntil(
CupertinoPageRoute(
builder: (BuildContext context) {
return HomePage();
},
),
(_) => false,
);
I Navigate successfully but when I click on this tab it throw this exception
════════ Exception caught by gesture ═══════════════════════════════════════════
The following assertion was thrown while handling a gesture:
Looking up a deactivated widget's ancestor is unsafe.
At this point the state of the widget's element tree is no longer stable.
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.
I even don't know the reason as well as solution so any help will be appreciated.
You are removing all the screens below HomePage from the stack.
pushAndRemoveUntil as name suggests pushes a new Screen in stack and removes all the other screens from stack as a result theirs no screen available to pop except the current HomePage.
Instead use only
if (mounted) {
Navigator.of(context).push(
CupertinoPageRoute(
builder: (BuildContext context) {
return HomePage();
},
),
(_) => false,
);
}
I want to share some data across different widgets so I decided to use a ChangeNotifierProvider<Example> with its relative Consumer<Example>. I have already used Providers before but never in this way (in fact I got some errors).
ChangeNotifierProvider<Example> has been defined in menu page while Consumer<Example> in an other widget defined in menu too.
Menu page :
class Menu extends StatefulWidget {
//...SOme code
ChangeNotifierProvider<Example>(
create: (context) => Example(),
child: ShowMultipleAnswers()
//...some code
And now I would like to use Consumer<Example> inside ShowMultipleAnswers() widget consuming data created in menu like :
class ShowMultipleAnswers extends StatefulWidget {
//...some code
Widget build(BuildContext context) {
return Consumer<Example>(builder: (context, handler, child) {
//some code
But I got these errors :
Error: Could not find the correct Provider<Example> above this Consumer<Example> Widget
This happens because you used a `BuildContext` that does not include the provider
of your choice. There are a few common scenarios:
- You added a new provider in your `main.dart` and performed a hot-reload.
To fix, perform a hot-restart.
- The provider you are trying to read is in a different route.
Providers are "scoped". So if you insert of provider inside a route, then
other routes will not be able to access that provider.
- You used a `BuildContext` that is an ancestor of the provider you are trying to read.
consider using `builder` like so:
Make sure that Consumer<Example> is under your MultiProvider/Provider<Example>.
This usually happens when you are creating a provider and trying to read it immediately.
For example, instead of:
```
Widget build(BuildContext context) {
return Provider<Example>(
create: (_) => Example(),
// Will throw a ProviderNotFoundError, because `context` is associated
// to the widget that is the parent of `Provider<Example>`
child: Text(context.watch<Example>()),
),
}
```
```
Widget build(BuildContext context) {
return Provider<Example>(
create: (_) => Example(),
// we use `builder` to obtain a new `BuildContext` that has access to the provider
builder: (context) {
// No longer throws
return Text(context.watch<Example>()),
}
),
}
```
I think the most valid options are 2 :
- The provider you are trying to read is in a different route.
But I don't know because they should be in the same, I mean ShowMultipleAnswers() is the Provider child.
Or the second
- You used a `BuildContext` that is an ancestor of the provider you are trying to read.
In this case, following suggestions above, I should use a builder:(context){} instead of directly calling child : .. but I read that after provider 5 builder has been substituted by create so I'm confused.
If I'm using wrong widgets tell me please!
The error message exactly specifies and describe your error
ShowMultipleAnswers got built using Menu context which doesn't have the Example provider, thus it throws this error.
you can either use builder attribute instead of child or wrap your MaterialApp with the provider
your code should be something like this:
class Menu extends StatefulWidget {
//...SOme code
ChangeNotifierProvider<Example>(
create: (context) => Example(),
builder: (context) {
return ShowMultipleAnswers();
}
//...some code
I forgot to say that there was an other page between Menu and ShowMultipleAnswers, like a bridge between them so the real flow was :
Menu Page -> Bridge Page -> ShowMultipleAnswers Page.
I removed this Bridge Page and it worked! But I still don't understand why it didn't work, maybe because Bridge Page didn't have any references of its Provider?
I'm using Riverpod as global state manager on my application; in this case, I'm using it to handle the application's launch: if there is a profile persited on device, it will go directly to one screen based on the user's role, if there is no such profile, it will send us to the login screen.
Given a persisted user I am getting the next bug:
======== Exception caught by widgets library =======================================================
The following assertion was thrown building Tooltip("Open navigation menu", dirty, state: _TooltipState#4e2ac(ticker inactive)):
No Overlay widget found.
Tooltip widgets require an Overlay widget ancestor for correct operation.
The most common way to add an Overlay to an application is to include a MaterialApp or Navigator widget in the runApp() call.
The specific widget that failed to find an overlay was: Tooltip
"Open navigation menu"
The relevant error-causing widget was:
AppBar file:///home/luisalaguna/Projects/thesis_cancer/lib/core/presentation/widgets/header.dart:17:12
When the exception was thrown, this was the stack:
#0 Overlay.of.<anonymous closure> (package:flutter/src/widgets/overlay.dart:306:9)
#1 Overlay.of (package:flutter/src/widgets/overlay.dart:309:6)
#2 _TooltipState.build (package:flutter/src/material/tooltip.dart:457:20)
#3 StatefulElement.build (package:flutter/src/widgets/framework.dart:4612:27)
#4 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4495:15)
Header is an AppBar widget; this bug would not be strange if all the widget wouldn't be wrapped by an Scaffold and a MaterialApp widgets:
The code on main file is this:
class CancerApp extends HookWidget {
#override
Widget build(BuildContext context) {
final _appRouter = AppRouter();
final bool darkTheme = useProvider(darkThemeProvider);
final launcherState = useProvider(launcherProvider);
SystemChrome.setEnabledSystemUIOverlays([SystemUiOverlay.bottom]);
return MaterialApp.router(
title: 'Thesis Cancer',
theme: darkTheme ? ThemeData.dark() : ThemeData.light(),
routerDelegate: _appRouter.delegate(),
routeInformationParser: _appRouter.defaultRouteParser(),
// home: SplashScreen()
builder: (context, router) => launcherState.when(
loading: () => SplashScreen(),
needsProfile: () => LoginPage(),
profileLoaded: () => MainScreen()),
);
}
}
About the launcher notifier, you can see it here.
After rafactoring this workflow I am getting this bug, i didn't get it when the profileLoaded state was returning the user(I was getting another issue).
What can be the problem?
Add applyElevationOverlayColor: true, on your Theme
Hello I am facing an issue with my flutter app using providers and consumer.
everything works fine how ever I have this issue in my debugger:
════════ Exception caught by foundation library ════════════════════════════════
The following assertion was thrown while dispatching notifications for CatergoryProvider:
setState() or markNeedsBuild() called during build.
This _InheritedProviderScope<CatergoryProvider> widget cannot be marked as needing to build because the framework is already in the process of building widgets. A widget can be marked as needing to be built during the build phase only if one of its ancestors is currently building. This exception is allowed because the framework builds parent widgets before children, which means a dirty descendant will always be built. Otherwise, the framework might not visit this widget during this build phase.
The widget on which setState() or markNeedsBuild() was called was: _InheritedProviderScope<CatergoryProvider>
value: Instance of 'CatergoryProvider'
listening to value
The widget which was currently being built when the offending call was made was: Consumer<CatergoryProvider>
dirty
dependencies: [_InheritedProviderScope<CatergoryProvider>]
When the exception was thrown, this was the stack
#0 Element.markNeedsBuild.<anonymous closure>
package:flutter/…/widgets/framework.dart:4138
#1 Element.markNeedsBuild
package:flutter/…/widgets/framework.dart:4153
#2 _InheritedProviderScopeElement.markNeedsNotifyDependents
package:provider/src/inherited_provider.dart:496
#3 ChangeNotifier.notifyListeners
package:flutter/…/foundation/change_notifier.dart:243
#4 CatergoryProvider.setLoading
package:quizz_app/provider/catergoryProvider.dart:43
...
The CatergoryProvider sending notification was: Instance of 'CatergoryProvider'
here is the consumer in question:
Consumer<CatergoryProvider>(
builder: (context, catergory, child) {
if (!catergory.isLoading() && !catergory.isList()) {
catergory.fetchCatergory();
}
catergories = catergory.getList();
return catergory.isLoading()
? ModalProgressHUD(
opacity: 0,
inAsyncCall: catergory.isLoading(),
child: Container())
: catergoryPage(catergories, context);
},
),
and this is where the stack trace leads me to:
void setLoading(value) {
loading = value;
notifyListeners();
}
It looks like you are probably calling setLoading(value) inside of a build method.. This would try to trigger a rebuild of the widget when notifyListeners() is invoked during the build of the widget.
Consider using a FutureBuilder or a StreamBuilder to change state depending when waiting on an async action.