flutterBlue.connect(device, timeout : const Duration(seconds: 10), ).listen(null);在 flutter 中

Question

对不起，我是初学者，我的英语很差我在 Flutter 遇到了麻烦。我引用 https://pub.dartlang.org/packages/flutter_blue我想使用 flutter 与耳温计设备进行通信。当我重新打开蓝牙并且它可以工作时，但是我重新打开应用程序并执行第二次它显示错误。我猜蓝牙 gatt cahce 导致错误。我该如何解决？

我的代码

deviceConnection = flutterBlue.scan(timeout: const Duration(seconds: 5),).listen((scanResult) async {
    device = scanResult.device;
    deviceConnection2 = await flutterBlue.connect(device, timeout: const Duration(seconds: 10),).listen(null);//this line error is error 1
    deviceStateSubscription = device.onStateChanged().listen((s) async {
        await device.discoverServices().then((s) async {//this is error 2
            .........
        }
    }
}

它显示这些错误

错误 1

Dart Error: Unhandled exception: PlatformException(already_connected, connection with device already exists, null)

错误2

Dart Error: Unhandled exception: PlatformException(get_services_error, no instance of BluetoothGatt, have you connected first?, null)

Answer 1

错误 1

Dart Error: Unhandled exception: PlatformException(already_connected, connection with device already exists, null)

由于该应用检测到蓝牙设备已连接，一种解决方法是检查是否有任何已连接的设备将其断开。您可以创建一个像 this GitHub thread 中那样执行此操作的函数:

What you can do here is that you check for any connected devices andthen disconnect them. I have written a function that does just that,here it is:

checkConnectedDevices() async{

    connectedDevices = await flutterBlue.connectedDevices.whenComplete((){
      print(connectedDevices);
      for(int i = 0; i < connectedDevices.length; i++){
        connectedDevices[i].disconnect();
      }
    });

  }

---

错误 2

Dart Error: Unhandled exception: PlatformException(get_services_error, no instance of BluetoothGatt, have you connected first?, null)

由于连接到设备时出错，您将无法调用 discoverServices()。因为你需要连接到设备才能调用这个函数。检查以下与此错误相关的 GitHub 讨论:

• connected ' discoverServices ' is't get #426
• discoverServices is broken #535