在导航器弹出时抛出错误，直到: “ !_degugLocked’: 不为真。”

Instead of giving you a direct answer, I'm going to walk you through how I thought about this when I saw the question, in the hope that it'll help you in the future.

Let's take a look at the assertion. It says Failed assertion: line 1995 pos 12: '!_debugLocked': I/flutter (24830): is not true.. Hmm, interesting. Let's take a look at that line of code.

assert(!_debugLocked);

Well, that doesn't give me much more information, let's look at the variable.

bool _debugLocked = false; // used to prevent re-entrant calls to push, pop, and friends

That's better. It's there to prevent re-entrant calls to push, pop, etc (by that it means that it doesn't want you calling 'push', 'pop', etc from within a call to 'push', 'pop'). So let's trace that back to your code.

This seems like the likely culprit:

bottomSheet.closed.then((v) {
Navigator.of(context)
.popUntil((r) => r.settings.isInitialRoute);
});

I'm going to skip a step here and use deductive reasoning instead - I'm betting that the closed future is finished during a pop. Go ahead and confirm that by reading the code if you feel like it.

So, if the issue is that we're calling pop from within a pop function, we need to figure out a way to defer the call to pop until after the pop has completed.

This becomes quite simple - there's two ways to do this. The simple way is to just use a delayed future with zero delay, which will have dart schedule the call as soon as possible once the current call stack returns to the event loop:

Future.delayed(Duration.zero, () {
Navigator. ...
});

The other more flutter-y way of doing it would be to use the Scheduler to schedule a call for after the current build/render cycle is done:

SchedulerBinding.instance.addPostFrameCallback((_) {
Navigator. ...
});

Either way should eliminate the problem you're having.

Another option is also possible though - in your ExtendedFloatingActionButton where you call pop:

ExtendedFloatingActionButton(
text: "ORDER DETAILS",
action: () {
Navigator.of(context).pop();
},
),

you could instead simply do the call to Navigator.of(context).popUntil.... That would eliminate the need for the doing anything after bottomSheet.closed is called. However, depending on whatever else you might or might not need to do in your logic this may not be ideal (I can definitely see the issue with having the bottom sheet set off a change to the main part of the page and why you've tried to make that happen in the page's logic).

Also, when you're writing your code I'd highly recommend separating it into widgets - for example the bottom sheet should be its own widget. The more you have in a build function, the harder it is to follow and it can actually have an effect on performance as well. You should also avoid using GlobalKey instances wherever possible - you can generally either pass objects (or callbacks) down if it's only through a few layers, use the .of(context) pattern, or use inherited widgets.

I had similar error, like a dialog box which had a logout button, which when pressed goes to login screen, but an _debugLocked error occurs, so I used

Navigator.of(context).pushNamedAndRemoveUntil('/screen4', (Route<dynamic> route) => false);

This removes all routes in the stack so that user cannot go back to the previous routes after they have logged out.

Setting (Route<dynamic> route) => false will make sure that all routes before the pushed route are removed.

I don't know if this is the "real" solution but it helped me as a beginner to Flutter.

I had this same issue any answer not worked for me and this error doesn't explain any thing.

After going each line code i found that we cannot launch any state in build method like this

 @override
Widget build(BuildContext context) {
var viewmodel = Provider.of<ViewModel>(context);
Navigator.of(context).push(MaterialPageRoute(builder:
(context)=>CreateItemPage(viewmodel.catalogData))); // this is way i was getting error.


return Scaffold();
}

I was getting error in CreateItemPage screen because of that line.

Solution of this issue create button which call this line Navigator.of(context).push(MaterialPageRoute(builder: (context)=>CreateItemPage(viewmodel.catalogData)));

For me, it was coming because I created a cycle of pushes that was causing this error. For example,

In the Initial route which was /loading the code was pushing /home

class _LoadingState extends State<Loading> {
void getTime() async {
// DO SOME STUFF HERE
Navigator.pushNamed(context, '/home');
}


@override
void initState() {
super.initState();
getTime();
}

And in the /home initState I was pushing /loading creating a cycle.

class _HomeState extends State<Home> {
@override
void initState() {
super.initState();
Navigator.pushNamed(context, '/loading');
}

In resume, you just need to remove it from your initState. I would recomend extend the class with AfterLayout and inside the afterFirstLayout you can redirect it to the page you want. This will garantee that everything is ok before routing.

See bellow the steps: Add to pubspec: after_layout: ^1.0.7+2

Then, You will extend it to the class you want to use. In my case was a statefull widget named HomePage. So it will looks like:

class HomePage extends StatefulWidget {
@override
HomePageState createState() => HomePageState();
} //no changes here




class HomePageState extends State<HomePage> with AfterLayoutMixin<HomePage> {
//the with AfterLayoutMixin<pageName> is the only thing you need to change.

Now, you need to implement a method called afterlayout, that will be executed after the build is completed.

@override
Future<void> afterFirstLayout(BuildContext context) {


//your code here safetly
}

You can find information here: https://pub.dev/packages/after_layout

For those that still have the same issue, this help me to solve it.

navigationService.popUntil((_) => true);
navigationService.navigateTo(
'authentication',
);

basically i wait until the navigation finish setting everything and then call the navigateTo.

For those who are invoking the Navigator as part of the build process. I found that it will intermittently throwing asserting error on the debugLocked

I avoided this issue by wrapping with a addPostFrameCallback:

WidgetsBinding.instance.addPostFrameCallback((_) {
Navigator.pushReplacement(context, MaterialPageRoute(builder: (_) => MyPage()));
});

Add Some Delay Then Try to do this Your Problem will be Solved :

  Future.delayed(const Duration(milliseconds: 500), () {

// Here you can write your code

        setState(() {
Navigator.of(context).pushAndRemoveUntil(
MaterialPageRoute(builder: (context) => SetCategory()),
(route) => false);
});
});

I am using flutter version 2.3.3 I also faced this issue when i try to pop back into my home screen from a second screen with command Navigator.pop(context) I solved this issue by replacing this line of code with Navigator.of(context).pop(context) It worked fine for me hope it hepls

For people encountering this issue while using bloc, make sure you are using navigation in a BlocListener (or BlocConsumer's listener). In my case I was using Navigator inside BlocBuilder. I am new to Flutter/Bloc and the accepted answer resolved the problem, but was not the proper solution. Switching my BlocBuilder to a BlocConsumer allowed for me to navigate during specific states.

Example of using BlocConsumer, navigate when state is 'LoginSuccess':

BlocConsumer<LoginBloc, LoginState>(
listener: (BuildContext context, state) {
if (state is LoginSuccess) {
Navigator.of(context).pushReplacement(
// Add your route here
PageRouteBuilder(
pageBuilder: (_, __, ___) => BlocProvider.value(
value: BlocProvider.of<NavigationBloc>(context),
child: HomeScreen(),
),
),
);
}
},
// Only build when the state is not LoginSuccess
buildWhen: (previousState, state) {
return state is! LoginSuccess;
},
// Handle all states other than LoginSuccess here
builder: (BuildContext context, LoginState state) {
if (state is LoginLoading) {
return Center(child: CircularProgressIndicator());
} else .....

I got this error because my initialRoute was /login. However, the initialRoute is required to be /.

If the route name starts with a slash, then it is treated as a "deep link", and before this route is pushed, the routes leading to this one are pushed also. For example, if the route was /a/b/c, then the app would start with the four routes /, /a, /a/b, and /a/b/c loaded, in that order.

Here is a link to the docs for reference.

I've gotten this error due to a typo accidentally calling Navigator.of(context).push during my build(): E/flutter ( 6954): [ERROR:flutter/lib/ui/ui_dart_state.cc(198)] Unhandled Exception: 'package:flutter/src/widgets/navigator.dart': Failed assertion: line 2845 pos 18: '!navigator._debugLocked': is not true.

The simulator flashed a more informative error:

setState() or markNeedsBuild() called during build.
This Overlay 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:
Overlay-[LabeledGlobalKey<OverlayState>#de69b]
The widget which was currently being built when the offending call was made was:
FutureBuilder

Basically, you should not be trying to push/pop to a new route in the middle of a build. If you really need to, wait for the build to finish, which is why others are suggesting wrapping it in a SchedulerBinding.instance.addPostFrameCallback to execute after everything is rendered, but you probably should find a better way to do this outside of a build.

In my case, I typed: onTap: _onTap(context),

when I really meant to type: onTap: () => _onTap(context),

my _onTap handler was doing the Navigator push. I had forgotten to wrap my handler in a closure that captures the context it needs, and instead actually was executing it instead of passing onTap: my callback.

Dialog solution

For those who encounter this when calling Navigator.push(..) from a Dialog.

You need to do Navigator.pop(context);to programmatically close modal first, then call Navigator.push(..).

I had the same issue and took me some time to figure out. I was listening to the state on the screen based on which it will navigate to different screen. And then on button click I was changing that state and navigating to different screen which was causing an issue.