蓝牙使用 flutter 接收来自 OBD-II 扫描仪的数据

Question

我正在开发一个使用 Flutter 通过蓝牙与 OBD-II 扫描仪连接的应用程序。我尝试过 Flutter Blue 包和其他一些包，但它们没有向我显示任何可用的蓝牙设备（没有扫描结果），调试控制台内也没有任何错误消息。连接扫描仪后，我必须读取数据流。请指导我。这是代码

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

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

class MyApp extends StatelessWidget {
  final title = 'Flutter BLE Scan Demo';
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: title,
      home: MyHomePage(title: title),
    );
  }
}

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> {
  FlutterBlue flutterBlue = FlutterBlue.instance;
  List<ScanResult> scanResultList = [];
  bool _isScanning = false;

  @override
  initState() {
    super.initState();
    initBle();
  }

  void initBle() {
    flutterBlue.isScanning.listen((isScanning) {
      _isScanning = isScanning;
      setState(() {});
    });
  }

  scan() async {
    if (!_isScanning) {
      scanResultList.clear();
      flutterBlue.startScan(timeout: Duration(seconds: 4));
      flutterBlue.scanResults.listen((results) {
        scanResultList = results;
        setState(() {});
      });
    } else {

      flutterBlue.stopScan();
    }
  }

  Widget deviceSignal(ScanResult r) {
    return Text(r.rssi.toString());
  }

  Widget deviceMacAddress(ScanResult r) {
    return Text(r.device.id.id);
  }

  Widget deviceName(ScanResult r) {
    String name = '';

    if (r.device.name.isNotEmpty) {
      name = r.device.name;
    } else if (r.advertisementData.localName.isNotEmpty) {
      name = r.advertisementData.localName;
    } else {
      name = 'N/A';
    }
    return Text(name);
  }

  Widget leading(ScanResult r) {
    return CircleAvatar(
      child: Icon(
        Icons.bluetooth,
        color: Colors.white,
      ),
      backgroundColor: Colors.cyan,
    );
  }

  void onTap(ScanResult r) {
    print('${r.device.name}');
  }

  Widget listItem(ScanResult r) {
    return ListTile(
      onTap: () => onTap(r),
      leading: leading(r),
      title: deviceName(r),
      subtitle: deviceMacAddress(r),
      trailing: deviceSignal(r),
    );
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: ListView.separated(
          itemCount: scanResultList.length,
          itemBuilder: (context, index) {
            return listItem(scanResultList[index]);
          },
          separatorBuilder: (BuildContext context, int index) {
            return Divider();
          },
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: scan,
        child: Icon(_isScanning ? Icons.stop : Icons.search),
      ),
    );
  }
}

以下是权限：

<uses-permission android:name="android.permission.BLUETOOTH_PRIVILEGED" />
    <uses-permission android:name="android.permission.BLUETOOTH" />
    <uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
    
    <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>

提前致谢

Answer 1

你在 AndroidManifest 中尝试过这个吗：

<!-- New Bluetooth permissions in Android 12
https://developer.android.com/about/versions/12/features/bluetooth-permissions -->
<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" />