bluetooth_rfcomm_flutter 0.1.0

Flutter plugin that adds the Android native build for bluetooth_rfcomm (Bluetooth Classic RFCOMM serial). Add it to a Flutter app and use the bluetooth_rfcomm API.

example/lib/main.dart

import 'dart:async';
import 'dart:convert';
import 'dart:typed_data';

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

void main() => runApp(const ExampleApp());

class ExampleApp extends StatelessWidget {
  const ExampleApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'bluetooth_rfcomm example',
      theme: ThemeData(colorSchemeSeed: Colors.indigo, useMaterial3: true),
      home: const HomePage(),
    );
  }
}

class HomePage extends StatefulWidget {
  const HomePage({super.key});
  @override
  State<HomePage> createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  final _bt = BluetoothRfcomm.instance;
  final _devices = <BluetoothDevice>[];
  BluetoothConnection? _conn;
  StreamSubscription<Uint8List>? _rx;
  final _log = StringBuffer();
  final _input = TextEditingController();
  bool _scanning = false;

  Future<void> _refresh() async {
    final bonded = await _bt.bondedDevices();
    if (!mounted) return;
    setState(
      () => _devices
        ..clear()
        ..addAll(bonded),
    );
  }

  Future<void> _scan() async {
    setState(() => _scanning = true);
    final seen = {for (final d in _devices) d.id};
    final sub = _bt.startDiscovery().listen((r) {
      if (seen.add(r.device.id) && mounted) {
        setState(() => _devices.add(r.device));
      }
    });
    await Future<void>.delayed(const Duration(seconds: 8));
    await sub.cancel();
    await _bt.stopDiscovery();
    if (!mounted) return;
    setState(() => _scanning = false);
  }

  Future<void> _connect(BluetoothDevice device) async {
    try {
      final conn = await _bt.connect(
        device,
        timeout: const Duration(seconds: 15),
      );
      if (!mounted) {
        await conn.close();
        return;
      }
      _rx = conn.input.listen(
        (bytes) {
          if (mounted) {
            setState(
              () => _log.write(utf8.decode(bytes, allowMalformed: true)),
            );
          }
        },
        onDone: () {
          // Peer dropped: return to the device list instead of leaving a dead
          // connection on screen.
          unawaited(_rx?.cancel());
          if (mounted) {
            setState(() {
              _log.writeln('\n[disconnected]');
              _conn = null;
            });
          }
        },
      );
      setState(() => _conn = conn);
    } on BluetoothException catch (e) {
      if (mounted) {
        ScaffoldMessenger.of(
          context,
        ).showSnackBar(SnackBar(content: Text(e.message)));
      }
    }
  }

  Future<void> _disconnect() async {
    await _rx?.cancel();
    await _conn?.finish();
    if (!mounted) return;
    setState(() => _conn = null);
  }

  void _send(String text) {
    final conn = _conn;
    if (conn == null || !conn.isConnected) return;
    conn.add(Uint8List.fromList(utf8.encode('$text\r\n')));
  }

  @override
  void dispose() {
    _rx?.cancel();
    _conn?.close();
    _input.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    final connected = _conn != null;
    return Scaffold(
      appBar: AppBar(
        title: const Text('Bluetooth Classic'),
        actions: [
          IconButton(onPressed: _refresh, icon: const Icon(Icons.refresh)),
          IconButton(
            onPressed: _scanning ? null : _scan,
            icon: _scanning
                ? const SizedBox(
                    width: 18,
                    height: 18,
                    child: CircularProgressIndicator(strokeWidth: 2),
                  )
                : const Icon(Icons.search),
          ),
        ],
      ),
      body: connected ? _terminal() : _deviceList(),
    );
  }

  Widget _deviceList() => ListView(
    children: [
      for (final d in _devices)
        ListTile(
          leading: Icon(
            d.bondState.isBonded ? Icons.bluetooth_connected : Icons.bluetooth,
          ),
          title: Text(d.name ?? '(unknown)'),
          subtitle: Text('${d.id}'),
          trailing: d.rssi != null ? Text('${d.rssi} dBm') : null,
          onTap: () => _connect(d),
        ),
    ],
  );

  Widget _terminal() {
    return Column(
      children: [
        Expanded(
          child: Container(
            width: double.infinity,
            padding: const EdgeInsets.all(12),
            child: SingleChildScrollView(
              child: Text(
                _log.toString(),
                style: const TextStyle(fontFamily: 'monospace'),
              ),
            ),
          ),
        ),
        Padding(
          padding: const EdgeInsets.all(8),
          child: Row(
            children: [
              Expanded(
                child: TextField(
                  controller: _input,
                  decoration: const InputDecoration(hintText: 'send...'),
                  onSubmitted: (String t) {
                    _send(t);
                    _input.clear();
                  },
                ),
              ),
              IconButton(
                onPressed: _disconnect,
                icon: const Icon(Icons.link_off),
              ),
            ],
          ),
        ),
      ],
    );
  }
}