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大家好，感谢您阅读本文。

所以我有一个Bleno文件，为我的树莓派 4 配置蓝牙并等待连接。我还有一个使用flutter_blue库进行蓝牙通信的颤振应用程序。该应用程序搜索可用设备并连接到选定的设备。之后，我有一个按钮来发送数据并断开与所选设备的连接。

ISSUE： 当我发送数据时，我会通过特性，并且对于每个特性，写入属性都设置为 false。但是在 Bleno 文件中，我将 Characteristic 属性设置为“write”，所以它应该是真的

new bleno.PrimaryService({
    uuid: '1801',
    characteristics: [
        new bleno.Characteristic({
            value: null,
            uuid: '1801',
            properties: ['write', 'writeWithoutResponse', 'read'],
            onWriteRequest: (_, callback) => {
                console.log('Write request received !');
                callback();
            }
        }),
    ]
}),

我想我错过了一些东西 - 但经过大量研究后，我无法解决我的问题。我在 YouTube 上观看了一些解释 BLE 的视频，并尝试在 StackOverflow 上找到一些解决方案，但这些解决方案中的任何一个都可以解决我的问题。

如果我的问题不够清楚，请通知我。

布莱诺文件代码

var bleno = require('bleno');

_startAdvertising = () => {
    bleno.startAdvertising(
        'RaspberryPI',
        '1801'
    );
}

bleno.on('stateChange', (state) => {
    console.log('Bleno state changed. New state: ' + state);
    if (state === 'poweredOn') {
        _startAdvertising();
    } else {
        bleno.stopAdvertising();
    }
});

bleno.on('accept', (clientAddr) => {
    console.log('Stop advertising...');
    bleno.stopAdvertising();
    console.log('You are connected to the device: ' + clientAddr);
});

bleno.on('disconnect', (clientAddr) => {
    console.log('You are disconnected from the device: ' + clientAddr);
    _startAdvertising();
});

bleno.on('advertisingStop', (err) => {
    console.log('Advertising stopped...');
});

bleno.on('advertisingStart', (err) => {
    if (err) {
        console.log('An error occured when advertising started ! ' + err);
        return;
    }
    console.log('Configuring advertising...');
    bleno.setServices([
        new bleno.PrimaryService({
            uuid: '1801',
            characteristics: [
                new bleno.Characteristic({
                    value: null,
                    uuid: '1801',
                    properties: ['write', 'writeWithoutResponse', 'read'],
                    onWriteRequest: (_, callback) => {
                        console.log('Write request received !');
                        callback();
                    }
                }),
            ]
        }),
    ]);
    console.log('Advertising started...');
});

颤振应用代码

import 'dart:convert';

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

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: SafeArea(child: BluetoothApp()),
    );
  }
}

class BluetoothApp extends StatefulWidget {
  BluetoothApp() : super();

  _BluetoothAppState createState() => _BluetoothAppState();
}

class _BluetoothAppState extends State<BluetoothApp> {
  bool isBluetoothOn = false;
  bool isPairing = false;
  bool isPaired = false;
  bool isScanning = false;
  FlutterBlue _blue = FlutterBlue.instance;
  List<BluetoothDevice> _devicesFounded = List<BluetoothDevice>();
  BluetoothDevice _device;

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

    _blue.isOn.then((state) {
      setState(() {
        isBluetoothOn = state;
      });
    });

    _blue.isScanning.listen((event) {
      setState(() {
        isScanning = event;
      });
    });

    _blue.state.listen((state) {
      setState(() {
        if (state == BluetoothState.off) {
          isBluetoothOn = false;
        } else {
          isBluetoothOn = true;
        }
      });
    });
  }

  void _scan() {
    print('Scanning...');
    _devicesFounded.clear();
    _blue.startScan();
    _blue.scanResults.listen((scan) {
      scan.forEach((element) {
        if (!_devicesFounded.contains(element.device)) {
          setState(() {
            _devicesFounded.add(element.device);
          });
        }
      });
    });
  }

  Widget _displayDevices() {
    return ListView.builder(
      physics: NeverScrollableScrollPhysics(),
      shrinkWrap: true,
      itemCount: _devicesFounded.length,
      itemBuilder: (context, index) {
        return Padding(
          padding: const EdgeInsets.fromLTRB(16, 8, 16, 8),
          child: Card(
            elevation: 4,
            child: ListTile(
              leading: Icon(Icons.devices),
              title: Text(_devicesFounded[index].name.isEmpty
                  ? "Unknow device"
                  : _devicesFounded[index].name),
              subtitle: Text(_devicesFounded[index].id.toString()),
              onTap: () async {
                setState(() {
                  _device = _devicesFounded[index];
                  isPairing = true;
                });
                await _device.connect();
                setState(() {
                  isPairing = false;
                  isPaired = true;
                });
              },
            ),
          ),
        );
      },
    );
  }

  void _discoverServices(BluetoothDevice device) async {
    BluetoothCharacteristic bluetoothCharacteristic;
    List<BluetoothService> services = await device.discoverServices();

    services.forEach((service) {
      service.characteristics.forEach((servChar) async {
        print(servChar.properties.toString());
        print('Properties WRITE = ' + servChar.properties.write.toString());
        if (servChar.properties.write) {
          try {
            await servChar.write(utf8.encode("Hello World"));
          } catch (err) {
            print('\n\nAn error occured: ' + err.toString() + '\n\n');
          }
        }
      });
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        floatingActionButton: FloatingActionButton(
            onPressed: () {
              if (!isScanning) {
                _scan();
                setState(() {
                  isScanning = true;
                });
              } else {
                _blue.stopScan();
                setState(() {
                  isScanning = false;
                });
              }
            },
            child: isScanning ? Icon(Icons.pause) : Icon(Icons.play_arrow)),
        body: !isBluetoothOn
            ? Center(child: Text('Please turn on the bluetooth !'))
            : isPairing
                ? Center(
                    child: Column(
                        mainAxisAlignment: MainAxisAlignment.center,
                        children: [
                          CircularProgressIndicator(),
                          Text('Connecting to the device...')
                        ]),
                  )
                : isPaired
                    ? Center(
                        child: Column(
                            mainAxisAlignment: MainAxisAlignment.center,
                            children: [
                              Text('You are connected to the device: ' +
                                  _device.name),
                              FlatButton(
                                child: Text('Send data'),
                                onPressed: () async {
                                  await _discoverServices(_device);
                                },
                              ),
                              FlatButton(
                                child: Text('Disconnect'),
                                onPressed: () async {
                                  setState(() {
                                    isPaired = false;
                                  });
                                  await _device.disconnect();
                                },
                              )
                            ]),
                      )
                    : _displayDevices()
          );
  }
}
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