main.dart

/// Flutter code sample for LogicalKeyboardKey
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';

void main() => runApp(MyApp());

/// This is the main application widget.
class MyApp extends StatelessWidget {
  static const String _title = 'Flutter Code Sample';

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: _title,
      home: Scaffold(
        appBar: AppBar(title: const Text(_title)),
        body: MyStatefulWidget(),
      ),
    );
  }
}

/// This is the stateful widget that the main application instantiates.
class MyStatefulWidget extends StatefulWidget {
  MyStatefulWidget({Key key}) : super(key: key);

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

/// This is the private State class that goes with MyStatefulWidget.
class _MyStatefulWidgetState extends State<MyStatefulWidget> {
  // The node used to request the keyboard focus.
  final FocusNode _focusNode = FocusNode();
// The message to display.
  String _message;

// Focus nodes need to be disposed.
  @override
  void dispose() {
    _focusNode.dispose();
    super.dispose();
  }

// Handles the key events from the RawKeyboardListener and update the
// _message.
  void _handleKeyEvent(RawKeyEvent event) {
    setState(() {
      _message = (event.isControlPressed ? 'CTRL + ' : '') +
          "0x" +
          event.logicalKey.keyId.toRadixString(16) +
          '\n' +
          event.logicalKey.toString();
    });
    print("0x" + event.logicalKey.keyId.toRadixString(16));
  }

  @override
  Widget build(BuildContext context) {
    final TextTheme textTheme = Theme.of(context).textTheme;
    return Container(
      color: Colors.white,
      alignment: Alignment.center,
      child: DefaultTextStyle(
        style: textTheme.headline4,
        child: RawKeyboardListener(
          focusNode: _focusNode,
          onKey: _handleKeyEvent,
          child: AnimatedBuilder(
            animation: _focusNode,
            builder: (BuildContext context, Widget child) {
              if (!_focusNode.hasFocus) {
                return GestureDetector(
                  onTap: () {
                    FocusScope.of(context).requestFocus(_focusNode);
                  },
                  child: const Text('Tap to focus'),
                );
              }
              return Text(_message ?? 'Press a key');
            },
          ),
        ),
      ),
    );
  }
}