Flutter error: Each child must be laid out exactly once. On building layout

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I'm starting to work with flutter. It seems pretty nice and easy, but there is not much resources when it comes to errors. Anyway, after long hours of thinking, checking and improvising, I started to search the net for answers and well, there was non. So I'd like to ask all of you, maybe someone will be able to explain to me why I get that error, what does it mean and how to get rid of it.

Oh, and before I will go in deep, I probably should mention I'm using flutter_bloc.

Ok so I've got code like this:

class Settings extends StatelessWidget {
  final _formKey = GlobalKey<FormState>();
  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
          title: new Text("SomeApp",style: TextStyle(color: Colors.white)),
          automaticallyImplyLeading: false,
          backgroundColor: myBlue.shade50,

          actions: <Widget>[
            IconButton(
              icon: new Icon(FontAwesomeIcons.download,color:  Colors.white),
              onPressed: () {
                Navigator.push(
                  context,
                  MaterialPageRoute(builder: (context) => DownloadView()),
                );
              },
            ),
            IconButton(
              icon: new Icon(FontAwesomeIcons.chevronCircleLeft,color:  Colors.white),
              onPressed: () {
                Navigator.push(
                  context,
                  MaterialPageRoute(builder: (context) => MainWindow()),
                );
              },
            ),]
      ),
      body: Container(
        padding: EdgeInsets.symmetric(vertical: 16),
        alignment: Alignment.center,
        child: new BlocBuilder<SettingsBloc, SettingsState>(
          builder: (context, state) {
            if (state is SettingsNotLoaded) {
              return new Center(
                  child: Text(
                    'count1',
                    style: TextStyle(fontSize: 24.0,color: Colors.black),
                  )
              );
            } else if (state is SettingsLoaded) {  
              return new Center(
                  child: Text(
                    'count2',
                    style: TextStyle(fontSize: 24.0,color: Colors.black),
                  )
              );
            }
            else
              {
                return new Center(
                    child: Text(
                      'count3',
                      style: TextStyle(fontSize: 24.0,color: Colors.black),
                    )
                );
              }
          },
        ),

      ),
    );
  }

And when starting my app I see the appBar just the way I want, but I do not see any text in body (I should see either count1, count2 or count3), but instead I get the error: "Each child must be laid out exactly once." referring to line 5 - return new Scaffold( . Seriously, this is driving me crazy. Do anyone know anything?

Thanks in advance and best regards to everyone!

PS. Ofcourse looked for info on flutter_bloc page, on https://flutter.dev/docs/development/ui/layout/tutorial ,here and in google as well.

Edit 1 Some grammatical errors Edit 2 Added edits info

Hi i just had the same problem i think its just a bug in flutter.Stop and then reinstall your app

Very weird error messages compiling simple apps � Issue #48655 , Flutter error: Each child must be laid out exactly once. On building layout. 703 Views. 0. Votes. Ask the child to update its layout within the limits specified by the constraints parameter. The child's size is returned. Call this from your performLayout function to lay out each child. Every child must be laid out using this function exactly once each time the performLayout function is called. Implementation

It's not a bug from flutter, I had faced the same issue, although the above solution is correct it seems to fail sometimes.

Try the following command

flutter clean

then run again

flutter run

or

alternatively, if you're on Android Studio (flutter plugins enabled)

Go to Tools > Flutter > Flutter Clean

then run the app again, will do the same as the above commands

EDIT: After being familiar with Flutter for about a week, now I do understand that making changes in code such as adding in a new dependency in pubspec.yaml requires stopping the app and Running again, I did notice that the GUI in the IDE (I use Android Studio) might have some issue, the above commands in the command line works just fine.

Happy Coding :)

Error with basic chart � Issue #45 � google/charts � GitHub, Doctor summary (to see all details, run flutter doctor -v): [√] Flutter (Channel I/ flutter ( 8056): #3 DicePage.build (package:dice/main.dart:28:14) I/flutter ( 8759 ): The following assertion was thrown during layout: I/flutter ( 8971): Another exception was thrown: Each child must be laid out exactly once. I/flutter (23766): chartContainer: RenderErrorBox#5b0e9 NEEDS-LAYOUT NEEDS-PAINT I/flutter (23766): Each child must be laid out exactly once. I/flutter (23766): Caught error: type '(Resultado, int) => String' is not a subtype of type '(dynamic, int) => String'

Recently I had the same error.

In my case the error was caused by nesting two Expanded Widgets into each other.

The error has gone by removing the parent Expanded Widget.

layoutChild method - MultiChildLayoutDelegate class , Could you please check if it is a bug or I'm doing something wrong. developers working together to host and review code, manage projects, and build software together. custom multichild layout delegate forgot to lay out the following child: I/flutter (23766): Each child must be laid out exactly once. Flutter : RenderBox was not laid out: RenderRepaintBoundary#58c65 relayoutBoundary=up1 NEEDS-PAINT 1 RenderBox was not laid out: RenderFlex#4a60a NEEDS-PAINT NEEDS-COMPOSITING-BITS-UPDATE

Try the following:

  1. Stop the simulation.
  2. Go to Android virtual device manager.
  3. Go to "Action" in the virtual device.
  4. Click the down arrow to see the option.
  5. Click "wipe data"
  6. Run the simulation again.

It worked with me for Android devices.

Every child must be laid out using this function exactly once each time the Size layoutChild(Object childId, BoxConstraints constraints) { final RenderBox child = _idToChild[childId]; assert(() { if (child == null) { throw FlutterError( 'The $this� If you want the Scaffold’s child to be exactly the same size as the Scaffold itself, you can wrap its child with SizedBox.expand. Note: When a widget tells its child that it must be of a certain size, we say the widget supplies tight constraints to its child. Tight vs. loose constraints

I had the same issue when i performed a hot reload, then i performed a hot restart and it went away. Looks like a Flutter bug.

Next, diagram each row. The first row, called the Title section, has 3 children: a column of text, a star icon, and a number. Its first child, the column, contains 2 lines of text. That first column takes a lot of space, so it must be wrapped in an Expanded widget.

Comments
  • what happened if you remove the BlocBuilder first?
  • if i remove whole bloc pattern with blocBuilder and just put text widget everything works fine
  • any fix on this? It happened to me too
  • have you debugged it to see the value of state? new is opetional
  • Thank you, this fixed my issue also