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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);
myErrorsHandler.onErrorDetails(details);
};
PlatformDispatcher.instance.onError = (error, stack) {
myErrorsHandler.onError(error, stack);
return true;
};
runApp(const MyApp());
}
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>Report errors to a service
While one always tries to create apps that are free of bugs,
they’re sure to crop up from time to time.
Since buggy apps lead to unhappy users and customers,
it’s important to understand how often your users
experience bugs and where those bugs occur.
That way, you can prioritize the bugs with the
highest impact and work to fix them.How can you determine how often your users experiences bugs?
Whenever an error occurs, create a report containing the
error that occurred and the associated stacktrace.
You can then send the report to an error tracking
service, such as Bugsnag, Datadog,
Firebase Crashlytics, Rollbar, or Sentry.The error tracking service aggregates all of the crashes your users
experience and groups them together. This allows you to know how often your
app fails and where the users run into trouble.In this recipe, learn how to report errors to the
Sentry crash reporting service using
the following steps:<topic_end>
<topic_start>
1. Get a DSN from Sentry
Before reporting errors to Sentry, you need a “DSN” to uniquely identify
your app with the Sentry.io service.To get a DSN, use the following steps:<topic_end>
<topic_start>
2. Import the Sentry package
Import the sentry_flutter package into the app.
The sentry package makes it easier to send
error reports to the Sentry error tracking service.To add the sentry_flutter package as a dependency,
run flutter pub add:<topic_end>
<topic_start>
3. Initialize the Sentry SDK
Initialize the SDK to capture different unhandled errors automatically:
<code_start>import 'package:flutter/widgets.dart';