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child: column(
children: <widget>[
Text('Show material dialog'),
],
),
);
}
<code_end>
this code doesn’t make an explicit call to setState,
but it’s called by showDialog.
the build method isn’t the right place to call
showDialog because build can be called by the
framework for every frame, for example, during an animation.
how to fix it?
one way to avoid this error is to use the navigator API
to trigger the dialog as a route. in the following example,
there are two pages. the second page has a
dialog to be displayed upon entry.
when the user requests the second page by
clicking a button on the first page,
the navigator pushes two routes–one
for the second page and another for the dialog.
<code_start>
class FirstScreen extends StatelessWidget {
const FirstScreen({super.key});
@override
widget build(BuildContext context) {
return scaffold(
appBar: AppBar(
title: const Text('First screen'),
),
body: center(
child: ElevatedButton(
child: const Text('Launch screen'),
onPressed: () {
// navigate to the second screen using a named route.
Navigator.pushNamed(context, '/second');
// immediately show a dialog upon loading the second screen.
navigator.push(
context,
PageRouteBuilder(
barrierDismissible: true,
opaque: false,
pageBuilder: (_, anim1, anim2) => const MyDialog(),
),
);
},
),
),
);
}
}
<code_end>
<topic_end>
<topic_start>
the ScrollController is attached to multiple scroll views
this error can occur when multiple scrolling
widgets (such as ListView) appear on the
screen at the same time. it’s more likely for
this error to occur on a web or desktop app,
than a mobile app since it’s rare to encounter
this scenario on mobile.
for more information and to learn how to fix,
check out the following video on
PrimaryScrollController:
<topic_end>
<topic_start>
references
to learn more about how to debug errors,
especially layout errors in flutter,
check out the following resources:
<topic_end>
<topic_start>
handling errors in flutter
the flutter framework catches errors that occur during callbacks
triggered by the framework itself, including errors encountered
during the build, layout, and paint phases. errors that don’t occur
within flutter’s callbacks can’t be caught by the framework,
but you can handle them by setting up an error handler on the
PlatformDispatcher.
all errors caught by flutter are routed to the
FlutterError.onError handler. by default,
this calls FlutterError.presentError,
which dumps the error to the device logs.
when running from an IDE, the inspector overrides this
behavior so that errors can also be routed to the IDE’s
console, allowing you to inspect the
objects mentioned in the message.
info note
consider calling FlutterError.presentError
from your custom error handler in order to see
the logs in the console as well.
when an error occurs during the build phase,
the ErrorWidget.builder callback is
invoked to build the widget that is used
instead of the one that failed. by default,
in debug mode this shows an error message in red,
and in release mode this shows a gray background.
when errors occur without a flutter callback on the call stack,
they are handled by the PlatformDispatcher’s error callback. by default,