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this only prints errors and does nothing else.
you can customize these behaviors,
typically by setting them to values in
your void main() function.
below each error type handling is explained. at the bottom
there’s a code snippet which handles all types of errors. even
though you can just copy-paste the snippet, we recommend you
to first get acquainted with each of the error types.
<topic_end>
<topic_start>
errors caught by flutter
for example, to make your application quit immediately any time an
error is caught by flutter in release mode, you could use the
following handler:
<code_start>
import 'dart:io';
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
void main() {
FlutterError.onError = (details) {
FlutterError.presentError(details);
if (kreleasemode) exit(1);
};
runApp(const MyApp());
}
// rest of `flutter create` code...
<code_end>
info note
the top-level kReleaseMode constant indicates
whether the app was compiled in release mode.
this handler can also be used to report errors to a logging service.
for more details, see our cookbook chapter for
reporting errors to a service.
<topic_end>
<topic_start>
define a custom error widget for build phase errors
to define a customized error widget that displays whenever
the builder fails to build a widget, use MaterialApp.builder.
<code_start>
class MyApp extends StatelessWidget {
const MyApp({super.key});
@override
widget build(BuildContext context) {
return MaterialApp(
builder: (context, widget) {
widget error = const text('...rendering error...');
if (widget is scaffold || widget is navigator) {
error = scaffold(body: center(child: error));
}
ErrorWidget.builder = (errordetails) => error;
if (widget != null) return widget;
throw StateError('widget is null');
},
);
}
}
<code_end>
<topic_end>
<topic_start>
errors not caught by flutter
consider an onPressed callback that invokes an asynchronous function,
such as MethodChannel.invokeMethod (or pretty much any plugin).
for example:
<code_start>
OutlinedButton(
child: const Text('Click me!'),
onPressed: () async {
const channel = MethodChannel('crashy-custom-channel');
await channel.invokeMethod('blah');
},
)
<code_end>
if invokeMethod throws an error, it won’t be forwarded to FlutterError.onError.
instead, it’s forwarded to the PlatformDispatcher.
to catch such an error, use PlatformDispatcher.instance.onError.
<code_start>
import 'package:flutter/material.dart';
import 'dart:ui';
void main() {
MyBackend myBackend = MyBackend();
PlatformDispatcher.instance.onError = (error, stack) {
myBackend.sendError(error, stack);
return true;
};
runApp(const MyApp());
}
<code_end>
<topic_end>
<topic_start>
handling all types of errors
say you want to exit application on any exception and to display
a custom error widget whenever a widget building fails - you can base
your errors handling on next code snippet:
<code_start>
import 'package:flutter/material.dart';
import 'dart:ui';
future<void> main() async {
await myErrorsHandler.initialize();
FlutterError.onError = (details) {
FlutterError.presentError(details);