Flutter 中利用 BLE 蓝牙（基于 flutter_blue_plus）
本指南将详细介绍如安在 Flutter 应用中利用 flutter_blue_plus 插件实现 BLE 蓝牙功能，包括扫描、毗连、读写特性值等操作。1. 添加依赖
在 pubspec.yaml 中添加 flutter_blue_plus 依赖：
dependencies:
flutter:
sdk: flutter
flutter_blue_plus: ^1.10.0 # 使用最新版本
运行以下下令安装依赖：
flutter pub get
2. 配置权限
BLE 蓝牙需要蓝牙和位置权限。
Android
在 AndroidManifest.xml 中添加以下权限：
<uses-permission android:name="android.permission.BLUETOOTH"/>
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN"/>
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>
<uses-permission android:name="android.permission.BLUETOOTH_SCAN"/>
<uses-permission android:name="android.permission.BLUETOOTH_CONNECT"/>
对于 Android 12 及以上版本，还需要添加以下配置：
<uses-feature android:name="android.hardware.bluetooth_le" android:required="true"/>
<uses-feature android:name="android.hardware.location" android:required="true"/>
iOS
在 Info.plist 中添加以下权限：
<key>NSBluetoothAlwaysUsageDescription</key>
<string>我们需要访问蓝牙来连接设备</string>
<key>NSBluetoothPeripheralUsageDescription</key>
<string>我们需要访问蓝牙来连接设备</string>
<key>NSLocationAlwaysAndWhenInUseUsageDescription</key>
<string>我们需要访问位置来扫描蓝牙设备</string>
<key>NSLocationWhenInUseUsageDescription</key>
<string>我们需要访问位置来扫描蓝牙设备</string>
3. 封装 BLE 工具类
创建一个 BluetoothManager 类，封装 BLE 蓝牙的常用操作。
import 'package:flutter_blue_plus/flutter_blue_plus.dart';
class BluetoothManager {
static final BluetoothManager _instance = BluetoothManager._internal();
FlutterBluePlus flutterBlue = FlutterBluePlus.instance;
// 当前连接的设备
BluetoothDevice? _connectedDevice;
// 当前连接的服务和特征
BluetoothService? _connectedService;
BluetoothCharacteristic? _connectedCharacteristic;
// 扫描到的设备列表
List<BluetoothDevice> devices = [];
// 私有构造函数
BluetoothManager._internal();
// 单例模式
factory BluetoothManager() {
return _instance;
}
// 开始扫描设备
Future<void> startScan({Duration? timeout}) async {
devices.clear();
flutterBlue.startScan(timeout: timeout);
flutterBlue.scanResults.listen((results) {
for (ScanResult result in results) {
if (!devices.contains(result.device)) {
devices.add(result.device);
}
}
});
}
// 停止扫描
Future<void> stopScan() async {
flutterBlue.stopScan();
}
// 连接设备
Future<void> connectToDevice(BluetoothDevice device) async {
await device.connect();
_connectedDevice = device;
print('Connected to ${device.name}');
// 发现服务
List<BluetoothService> services = await device.discoverServices();
for (BluetoothService service in services) {
print('Service: ${service.uuid}');
for (BluetoothCharacteristic characteristic in service.characteristics) {
print('Characteristic: ${characteristic.uuid}');
}
}
}
// 断开连接
Future<void> disconnectDevice() async {
if (_connectedDevice != null) {
await _connectedDevice!.disconnect();
_connectedDevice = null;
_connectedService = null;
_connectedCharacteristic = null;
print('Disconnected');
}
}
// 设置当前服务和特征
void setConnectedServiceAndCharacteristic(
BluetoothService service, BluetoothCharacteristic characteristic) {
_connectedService = service;
_connectedCharacteristic = characteristic;
}
// 读取特征值
Future<List<int>> readCharacteristic() async {
if (_connectedCharacteristic != null) {
return await _connectedCharacteristic!.read();
}
throw Exception('No characteristic selected');
}
// 写入特征值
Future<void> writeCharacteristic(List<int> value) async {
if (_connectedCharacteristic != null) {
await _connectedCharacteristic!.write(value);
} else {
throw Exception('No characteristic selected');
}
}
// 监听特征值通知
Future<void> setNotification(bool enable) async {
if (_connectedCharacteristic != null) {
await _connectedCharacteristic!.setNotifyValue(enable);
if (enable) {
_connectedCharacteristic!.value.listen((value) {
print('Notification value: $value');
});
}
} else {
throw Exception('No characteristic selected');
}
}
// 获取已连接的设备
BluetoothDevice? get connectedDevice => _connectedDevice;
// 获取已连接的服务
BluetoothService? get connectedService => _connectedService;
// 获取已连接的特征
BluetoothCharacteristic? get connectedCharacteristic => _connectedCharacteristic;
}
4. 在 Flutter 应用中利用
以下是一个简单的 Flutter 应用示例，展示怎样利用 BluetoothManager 类。
import 'package:flutter/material.dart';
import 'bluetooth_manager.dart'; // 导入蓝牙工具类
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
home: BluetoothApp(),
);
}
}
class BluetoothApp extends StatefulWidget {
@override
_BluetoothAppState createState() => _BluetoothAppState();
}
class _BluetoothAppState extends State<BluetoothApp> {
final BluetoothManager bluetoothManager = BluetoothManager();
@override
void initState() {
super.initState();
bluetoothManager.startScan(timeout: Duration(seconds: 4));
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Flutter BLE Example'),
),
body: Column(
children: [
Expanded(
child: ListView.builder(
itemCount: bluetoothManager.devices.length,
itemBuilder: (context, index) {
return ListTile(
title: Text(bluetoothManager.devices.name ?? 'Unknown device'),
subtitle: Text(bluetoothManager.devices.id.toString()),
onTap: () async {
await bluetoothManager.connectToDevice(bluetoothManager.devices);
setState(() {});
},
);
},
),
),
if (bluetoothManager.connectedDevice != null)
Padding(
padding: const EdgeInsets.all(16.0),
child: Column(
children: [
Text('Connected to: ${bluetoothManager.connectedDevice!.name}'),
ElevatedButton(
onPressed: () async {
await bluetoothManager.disconnectDevice();
setState(() {});
},
child: Text('Disconnect'),
),
],
),
),
],
),
);
}
}
5. 功能阐明
扫描设备：通过 startScan 方法扫描附近的 BLE 设备。
毗连设备：通过 connectToDevice 方法毗连设备，并自动发现服务和特性。
读写特性值：通过 readCharacteristic 和 writeCharacteristic 方法读写特性值。
监听通知：通过 setNotification 方法监听特性值的通知。
6. 注意事项
权限：确保在 Android 和 iOS 上精确配置蓝牙和位置权限。
动态权限请求：在高版本系统中，需要在运行时动态请求权限。
设备兼容性：不同设备的 BLE 实现大概有所不同，确保测试你的应用在各种设备上的兼容性。
通过以上步骤，你可以在 Flutter 应用中轻松实现 BLE 蓝牙功能。
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