在BLoC中添加一个StreamController来处理蓝牙状态，然后在BLoC中使用StreamBuilder进行视图构建。以下是一个示例代码：

class MyBloc extends Bloc {
  final BluetoothController _bluetoothController = BluetoothController();

  final _bluetoothStateController = StreamController();

  Stream get bluetoothState => _bluetoothStateController.stream;

  @override
  Stream mapEventToState(SomeEvent event) async* {
    if (event is BluetoothChangedEvent) {
      final currentState = state;
      yield currentState.copyWith(
        bluetoothState: event.bluetoothState,
      );
      _bluetoothStateController.add(event.bluetoothState);
    }
  }

  @override
  Future close() {
    _bluetoothStateController?.close();
    return super.close();
  }
}

class BluetoothWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return StreamBuilder(
      stream: context.watch().bluetoothState,
      builder: (context, snapshot) {
        final bluetoothState = snapshot.data;

        if (bluetoothState == BluetoothState.connected) {
          return Text('蓝牙已连接');
        } else if (bluetoothState == BluetoothState.disconnected) {
          return Text('蓝牙已断开');
        } else {
          return CircularProgressIndicator();
        }
      },
    );
  }
}