// Método que conecta o bluetooth
void _connect() {
   if (_device == null) {
      show(‘No device selected’);
   } else {
   bluetooth.isConnected.then((isConnected) {
      if (!isConnected) {
         bluetooth
         .connect(_device)
         .timeout(Duration(seconds: 10))
         .catchError((error) {
         setState(() => _pressed = false);
      });
         setState(() => _pressed = true);
         }
   });
   }
}

// Método que desconecta o bluetooth
void _disconnect() {
   bluetooth.disconnect();
   setState(() => _pressed = true);
}

// Método que exibe a Snackbar com a mensagem
Future show(
String message, {
Duration duration: const Duration(seconds: 3),
}) async {
   await new Future.delayed(new Duration(milliseconds: 100));
   _scaffoldKey.currentState.showSnackBar(
      new SnackBar(
         content: new Text(
         message,
         ),
         duration: duration,
      ),
   );
}