如何在 flutter/dart 中正确使用 flutter_reactive_ble writetocharacteristic 和 subscribetocharacteristic

问题描述

现在我有一个蓝牙模块，它会在收到每条消息时发回响应 所以如果我写到特征，我需要能够在读取订阅完成的响应之前等待。

我试过了：

subScribetocharacteristic(characteristic);
writeCharacterisiticWithoutResponse(characteristic,[1]);
readValuefromSubscribedCharacteristic();

但是我过早地读取了值（在模块响应之前）

已编辑：

这是我目前所拥有的，我该如何正确地做到这一点？

//this is a snippet from a dialog prompting user for password that pops up after onTap of listTile of a ble device list      
  //userData = user input password of this prompt
  //this is onpressed of that ok button for the password prompt dialog


  //creates a buffer variable
  List receiveData = [];

  onpressed: () async {
  //define characteristic
  final characteristic = QualifiedCharacteristic(characteristicId:characteristicId,serviceId: serviceId,deviceid: id);

  //subscribe to characteristic
  await ble.subscribetocharacteristic(characteristic).listen((event) {
    //if seq of data starts with byte 5550 its a match
    if (event[0] == 5 && event[1] == 5 && event[2] == 5 && event[3] == 0) {          
      print('New incoming data,inserting data to buffer');          
      receiveData = new Uint8List.fromList(event);          
    }

    print(event);        
    print(receiveData);
  });

  //send the unlock command with password
  await writeCharacteristicWithoutResponse(charateristic,userData);

  //check receiveData - result is something wrong with data if receiveData is []
  if (receiveData == Null) {
    //data is empty,so means there isnt something yet in the buffer
    print('Something wrong with data,it might be corrupt/loss packet');
  } else {
    // the module should return 1 at array[8] if module is unlocked
    if (receiveData[8] == 1) {
      //if its 1,module is unlocked and go back to prevIoUs page
      print('unlocked!!');
      Navigator.of(context).pop(userData);
    } else {
      //if its not,module is locked and reprompt the showDialog
      print('unlocked');
      
    }
  }    


  //clear receiveData afer read from it
  globals.receiveData = [0];    
}

解决方法

README 文件的使用部分描述了正确的过程，如下所示：

final characteristic = QualifiedCharacteristic(serviceId: serviceUuid,characteristicId: characteristicUuid,deviceId: foundDeviceId);
flutterReactiveBle.subscribeToCharacteristic(characteristic).listen((data) {
    // code to handle incoming data
},onError: (dynamic error) {
    // code to handle errors
});

编辑：

您应该将有关接收到的数据的所有内容都移动到 listen 方法中：

//this is a snippet from a dialog prompting user for password that pops up after onTap of listTile of a ble device list      
//userData = user input password of this prompt
//this is onPressed of that ok button for the password prompt dialog


//creates a buffer variable
List receiveData = [];

onPressed: () async {
    //define characteristic
    final characteristic = QualifiedCharacteristic(characteristicId:characteristicId,serviceId: serviceId,deviceId: id);

//subscribe to characteristic
await ble.subscribeToCharacteristic(characteristic).listen((event) {
    //if seq of data starts with byte 5550 its a match
    if (event[0] == 5 && event[1] == 5 && event[2] == 5 && event[3] == 0) {          
        print('New incoming data,inserting data to buffer');          
        receiveData = new Uint8List.fromList(event);          
    }

    print(event);        
    print(receiveData);

    //check receiveData - result is something wrong with data if receiveData is []
    if (receiveData == Null) {
        //data is empty,so means there isnt something yet in the buffer
        print('Something wrong with data,it might be corrupt/loss packet');
    } else {
        // the module should return 1 at array[8] if module is unlocked
        if (receiveData[8] == 1) {
            //if its 1,module is unlocked and go back to previous page
            print('unlocked!!');
            Navigator.of(context).pop(userData);
        } else {
            //if its not,module is locked and reprompt the showDialog
            print('unlocked');
      
        }
    }    

    //clear receiveData afer read from it
    globals.receiveData = [0];    
    });

    //send the unlock command with password
    await writeCharacteristicWithoutResponse(charateristic,userData);

}