Flutter RawKeyboardListener does not work in release mode

Question

I'm using RawKeyboardListener to capture keyboard events on web, it works fine in debug mode but when I build it for release it does not capture keyboard events. I tried it with a basic app:

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key? key, required this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }

  Future<void> _onEventKey(RawKeyEvent event) async {
    if (event.runtimeType.toString() == 'RawKeyDownEvent') {
      if (event.isKeyPressed(LogicalKeyboardKey.arrowLeft)) {
        _incrementCounter();
      }
    }
  }

  @override
  Widget build(BuildContext context) {
    return RawKeyboardListener(
      focusNode: FocusNode(),
      onKey: (RawKeyEvent event) async {
        await _onEventKey(event);
      },
      autofocus: true,
      child: Scaffold(
        appBar: AppBar(
          title: Text(widget.title),
        ),
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              Text(
                'You have pushed the button this many times:',
              ),
              Text(
                '$_counter',
                style: Theme.of(context).textTheme.headline4,
              ),
            ],
          ),
        ),
        floatingActionButton: FloatingActionButton(
          onPressed: _incrementCounter,
          tooltip: 'Increment',
          child: Icon(Icons.add),
        ), // This trailing comma makes auto-formatting nicer for build methods.
      ),
    );
  }
}

Is there anything i'm doing wrong?

Answer 1

Since generated javascript code is minified in release mode, there is no more type RawKeyDownEvent, but something like minified:qN.

Instead of

if (event.runtimeType.toString() == 'RawKeyDownEvent') {

you have to use a more accurate comparison:

if (event.runtimeType == RawKeyDownEvent) {

Here is fixed code (also removed unnecessary async/await):

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key? key, required this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }

  void _onEventKey(RawKeyEvent event) {
    // next line prints something like 'minified:qN' in production mode
    print(event.runtimeType.toString()); 
    // if (event.runtimeType.toString() == 'RawKeyDownEvent') {
    if (event.runtimeType == RawKeyDownEvent) {
      if (event.isKeyPressed(LogicalKeyboardKey.arrowLeft)) {
        _incrementCounter();
      }
    }
  }

  @override
  Widget build(BuildContext context) {
    return RawKeyboardListener(
      focusNode: FocusNode(),
      onKey: (RawKeyEvent event) {
        _onEventKey(event);
      },
      autofocus: true,
      child: Scaffold(
        appBar: AppBar(),
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              Text('You have pushed the button this many times:'),
              Text('$_counter', style: Theme.of(context).textTheme.headline4),
            ],
          ),
        ),
        floatingActionButton: FloatingActionButton(
          onPressed: _incrementCounter,
          tooltip: 'Increment',
          child: Icon(Icons.add),
        ),
      ),
    );
  }
}