Flutter蓝牙通信插件flutter_blue_classic的使用

Flutter_blue_classic 是一个用于与经典蓝牙设备（Bluetooth Classic devices）进行通信的Flutter插件。如果您想使用低功耗蓝牙（BLE）设备，建议考虑 flutter_blue_plus。

注意事项 - iOS

该插件目前仅支持Android平台。iOS不提供类似Android的经典蓝牙接口。在iOS上，您的BL设备必须是MFi (Made for iPod/iPhone)认证，并且您需要使用External Accessory Framework。由于这超出了本包的范围，您需要自行实现。

入门指南

minSdkVersion

此包仅兼容Android SDK 21或更高版本，请确保在android/app/build.gradle中设置正确的minSdkVersion。

权限

根据Android权限要求的不同情况，此包不在其清单文件中定义任何权限。因此，您需要自己声明它们。详细信息请参阅Android开发者文档中的权限部分。

不需要位置访问权限的情况

在android/app/src/main/AndroidManifest.xml中添加以下内容：

<!-- Permissions for Android 12 or above -->
<uses-permission android:name="android.permission.BLUETOOTH_SCAN" android:usesPermissionFlags="neverForLocation" />
<uses-permission android:name="android.permission.BLUETOOTH_CONNECT" />

    <!-- legacy for Android 11 or lower -->
<uses-permission android:name="android.permission.BLUETOOTH" android:maxSdkVersion="30" />
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN" android:maxSdkVersion="30" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" android:maxSdkVersion="30" />

    <!-- legacy for Android 9 or lower -->
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" android:maxSdkVersion="28" />

需要位置访问权限的情况

在android/app/src/main/AndroidManifest.xml中添加以下内容：

<!-- Permissions for Android 12 or above -->
<uses-permission android:name="android.permission.BLUETOOTH_SCAN" />
<uses-permission android:name="android.permission.BLUETOOTH_CONNECT" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />

    <!-- legacy for Android 11 or lower -->
<uses-permission android:name="android.permission.BLUETOOTH" android:maxSdkVersion="30" />
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN" android:maxSdkVersion="30" />

    <!-- legacy for Android 9 or lower -->
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" android:maxSdkVersion="28" />

然后在初始化插件时传递accessFineLocation参数：

final blueClassic = FlutterBlueClassic(usesFineLocation: true);

参考

FlutterBlueClassic

BluetoothConnection

示例代码

下面是一个完整的示例demo，展示了如何使用flutter_blue_classic插件来扫描、连接和与蓝牙设备通信。

import 'dart:async';

import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'package:flutter_blue_classic/flutter_blue_classic.dart';
import 'package:flutter_blue_classic_example/device_screen.dart';

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

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

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(home: MainScreen());
  }
}

class MainScreen extends StatefulWidget {
  const MainScreen({super.key});

  @override
  State<MainScreen> createState() => _MainScreenState();
}

class _MainScreenState extends State<MainScreen> {
  final _flutterBlueClassicPlugin = FlutterBlueClassic();

  BluetoothAdapterState _adapterState = BluetoothAdapterState.unknown;
  StreamSubscription? _adapterStateSubscription;

  final Set<BluetoothDevice> _scanResults = {};
  StreamSubscription? _scanSubscription;

  bool _isScanning = false;
  int? _connectingToIndex;
  StreamSubscription? _scanningStateSubscription;

  @override
  void initState() {
    super.initState();
    initPlatformState();
  }

  Future<void> initPlatformState() async {
    BluetoothAdapterState adapterState = _adapterState;

    try {
      adapterState = await _flutterBlueClassicPlugin.adapterStateNow;
      _adapterStateSubscription =
          _flutterBlueClassicPlugin.adapterState.listen((current) {
        if (mounted) setState(() => _adapterState = current);
      });
      _scanSubscription =
          _flutterBlueClassicPlugin.scanResults.listen((device) {
        if (mounted) setState(() => _scanResults.add(device));
      });
      _scanningStateSubscription =
          _flutterBlueClassicPlugin.isScanning.listen((isScanning) {
        if (mounted) setState(() => _isScanning = isScanning);
      });
    } catch (e) {
      if (kDebugMode) print(e);
    }

    if (!mounted) return;

    setState(() {
      _adapterState = adapterState;
    });
  }

  @override
  void dispose() {
    _adapterStateSubscription?.cancel();
    _scanSubscription?.cancel();
    _scanningStateSubscription?.cancel();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    List<BluetoothDevice> scanResults = _scanResults.toList();

    return Scaffold(
      appBar: AppBar(
        title: const Text('FlutterBlueClassic example app'),
      ),
      body: ListView(
        children: [
          ListTile(
            title: const Text("Bluetooth Adapter state"),
            subtitle: const Text("Tap to enable"),
            trailing: Text(_adapterState.name),
            leading: const Icon(Icons.settings_bluetooth),
            onTap: () => _flutterBlueClassicPlugin.turnOn(),
          ),
          const Divider(),
          if (scanResults.isEmpty)
            const Center(child: Text("No devices found yet"))
          else
            for (var (index, result) in scanResults.indexed)
              ListTile(
                title: Text("${result.name ?? "???"} (${result.address})"),
                subtitle: Text(
                    "Bondstate: ${result.bondState.name}, Device type: ${result.type.name}"),
                trailing: index == _connectingToIndex
                    ? const CircularProgressIndicator()
                    : Text("${result.rssi} dBm"),
                onTap: () async {
                  BluetoothConnection? connection;
                  setState(() => _connectingToIndex = index);
                  try {
                    connection =
                        await _flutterBlueClassicPlugin.connect(result.address);
                    if (!this.context.mounted) return;
                    if (connection != null && connection.isConnected) {
                      if (mounted) setState(() => _connectingToIndex = null);
                      Navigator.push(
                          context,
                          MaterialPageRoute(
                              builder: (context) =>
                                  DeviceScreen(connection: connection!)));
                    }
                  } catch (e) {
                    if (mounted) setState(() => _connectingToIndex = null);
                    if (kDebugMode) print(e);
                    connection?.dispose();
                    ScaffoldMessenger.maybeOf(context)?.showSnackBar(
                        const SnackBar(
                            content: Text("Error connecting to device")));
                  }
                },
              )
        ],
      ),
      floatingActionButton: FloatingActionButton.extended(
        onPressed: () {
          if (_isScanning) {
            _flutterBlueClassicPlugin.stopScan();
          } else {
            _scanResults.clear();
            _flutterBlueClassicPlugin.startScan();
          }
        },
        label: Text(_isScanning ? "Scanning..." : "Start device scan"),
        icon: Icon(_isScanning ? Icons.bluetooth_searching : Icons.bluetooth),
      ),
    );
  }
}

以上代码展示了一个简单的Flutter应用，它能够扫描附近的蓝牙设备并尝试连接。您可以在此基础上扩展功能，例如发送和接收数据等操作。希望这个示例能帮助您更好地理解和使用flutter_blue_classic插件。