Flutter蓝牙串口通信

Question

我有一个连接了 HC-06 蓝牙模块的微 Controller 。我想构建一个 flutter 应用程序，它可以与微 Controller 通信以通过蓝牙发送整数值，然后也从微 Controller 接收整数值。另一端的代码是用C编程写的。在我这边，我开始用 flutter 构建应用程序。我正在使用 flutter_bluetooth_serial 包。对于蓝牙连接，我使用了官方包github上示例中的一些代码。 https://github.com/edufolly/flutter_bluetooth_serial . (我将名为:BluetoothDeviceListEntry 的文件复制到我的项目中)。

接下来，我创建了应用程序的主页和蓝牙连接编码。这是我的 main.dart 文件:

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

}

class MyApp extends StatelessWidget {

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: HomePage() ,
      debugShowCheckedModeBanner: false,
    );
  }
}


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

class _HomePageState extends State<HomePage> with WidgetsBindingObserver {

  BluetoothState _bluetoothState = BluetoothState.UNKNOWN;

  List<BluetoothDevice> devices =  <BluetoothDevice>[];


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

    _getBTState();
    _stateChangeListener();
    _listBondedDevices();
    _stateChangeListener();
  }

  @override
  void dispose(){
    WidgetsBinding.instance!.removeObserver(this);
    super.dispose();

    @override
    void disChangeAppLifeCycleState(AppLifecycleState state){
      if(state.index == 0){
        //resume
        if(_bluetoothState.isEnabled){
          _listBondedDevices();
        }
      }
    }

  }
  _getBTState(){
    FlutterBluetoothSerial.instance.state.then((state){
      _bluetoothState = state;
      if(_bluetoothState.isEnabled){
        _listBondedDevices();
      }
      setState(() {});

    });
  }
  _stateChangeListener(){
    FlutterBluetoothSerial.instance.onStateChanged().listen((BluetoothState state) {
      _bluetoothState = state;
      if(_bluetoothState.isEnabled){
        _listBondedDevices();
      }else{
        devices.clear();
      }
      print("State isEnabled: ${state.isEnabled}");
      setState(() {});
    });

  }

  _listBondedDevices(){
    FlutterBluetoothSerial.instance.getBondedDevices().then((List<BluetoothDevice> bondedDevices){
      devices = bondedDevices;
      setState(() {});
    });


  }



  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text("Bluetooth Scanner"),),
      body: Container(
        child: Column(children: <Widget>[
          SwitchListTile(
            title: Text('Enable Bluetooth'),
            value: _bluetoothState.isEnabled,
            onChanged: (bool value){
              future() async{
                if(value){
                  await FlutterBluetoothSerial.instance.requestEnable();
                }else{
                  await FlutterBluetoothSerial.instance.requestDisable();
                }
                future().then((_){
                  setState(() {});
                });
              }
            },
          ),
          ListTile(
            title: Text("Bluetooth Status"),
            subtitle: Text(_bluetoothState.toString()),
            trailing: RaisedButton(child: Text("Settings"), onPressed: (){
              FlutterBluetoothSerial.instance.openSettings();
            },
           ),
          ),

          // adaptor code


          Expanded(
            child: ListView(
            children: devices
                .map((_device)=> BluetoothDeviceListEntry(
                    device: _device,
                    enabled: true,
                    onTap: (){
                      print("item");
                      _startDataCollection(context, _device);
                    },
                ))
                .toList(),
          ),
          ),

         // discovery code

            ],
          ),
      ),
      );
    }
    void _startDataCollection(BuildContext context, BluetoothDevice server){
    Navigator.of(context).push(MaterialPageRoute(builder: (context){
      return DetailPage(server: server);
    }));
    }
  }

当我按下配对设备时，函数 _startDataCollection 被触发，我转到另一个文件 (detailpage.dart)，这就是我开始痛苦的地方......

这里是详细页面的编码:

class DetailPage extends StatefulWidget {

  final BluetoothDevice server;

  DetailPage({required this.server});


  @override
  State<DetailPage> createState() => _DetailPageState();
}

class _DetailPageState extends State<DetailPage> {
  late BluetoothConnection connection;
  bool isConnecting = true;
  bool get isConnected => connection.isConnected;
  bool isDisconnecting = false;

  int _selectedvalue =0;

  int chunks = 0;
  int rcvdData = 0;
  int contentLength =0;
  late Uint8List _bytes;



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

    }

    @override
    void dispose() {
    if(isConnected){
      isDisconnecting = true;
      connection.dispose();
    }
    super.dispose();

    }

  _getBTConnection(){
    BluetoothConnection.toAddress(widget.server.address).then((_connection){
      connection = _connection;
      isConnecting = false;
      isDisconnecting = false;
      setState(() {});

      connection.input?.listen(_onDataReceived).onDone(() {
        if(isDisconnecting){
          print("Disconnecting locally");


        }else{
          print("Disconnecting remotely");

        }
        if(mounted){
          setState(() {});
        }
        Navigator.of(context).pop();

      });

    }).catchError((error){
      Navigator.of(context).pop();

    });
  }
 

  _onDataReceived(int data){
    if(data != null && data.bitLength > 0){
      chunks.add(data);

    

    }

  }


  Future<void> _sendMessageString() async {
    connection.output.add(ascii.encode('Hello!'));
    await connection.output.allSent;
    print('ok send message');
    }


  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Colors.grey,
      appBar: AppBar(title: (isConnecting ? Text('Connecting to ${widget.server.name} ...')
          : isConnected ? Text ('Connected with ${widget.server.name}') : Text(
          'Disconnected with ${widget.server.name}')),),
      body: SafeArea(child: isConnected

          ? Column(
        children: <Widget>[
         submitButton()
        ],
            )
          : const Center(
        child: Text(
          "Connecting ...",
          style: TextStyle(
              fontSize: 24,
              fontWeight: FontWeight.bold,
              color: Colors.white),

        ),
      ),

        ));
  }
  Widget submitButton(){
    return Container(
      padding: const EdgeInsets.all(16),
      child: ElevatedButton(
        
      onPressed: () {
        print (chunks);
        },
        child: const Padding(
          padding: EdgeInsets.all(8),
          child: Text("show value", style: TextStyle(fontSize: 24),
          ),

        ),
      ),
    );
  }
  
}

我想做的是，当我按下按钮(显示值)时，我想在编译器中打印接收到的数据，但出现 2 个错误。第一个是关于 _getBTConnection 函数:

"connection.input?.listen(_onDataReceived).onDone(()"

The argument type 'dynamic Function(int)' can't be assigned to the parameter type 'void Function(Uint8List)?'.

另一个是关于 (_onDataReceived) 函数:

The method 'add' isn't defined for the type 'int'.

我也尝试制作一些函数来发送整数，但似乎没有一个也能正常工作。如果有人可以帮我解决这个问题，因为我是 flutter 的新手

非常感谢

Answer 1

查看您提供的链接中的示例。传入数据的类型是 Uint8List 而不是 int。

try {
    BluetoothConnection connection = await BluetoothConnection.toAddress(address);
    print('Connected to the device');

    connection.input.listen((Uint8List data) {
        print('Data incoming: ${ascii.decode(data)}');
        ...
    }).onDone(() {
        print('Disconnected by remote request');
    });
}
catch (exception) {
    print('Cannot connect, exception occured');
}

使用ByteData从 data 中读取值。

final byteData = ByteData.sublistView(data);
final value = byteData.getFloat32(0);