I need help printing in a GX420t

  {

   Handler handler = new Handler();

   handler.post(new Runnable()

  {

   UsbDeviceConnection conn;

   UsbInterface usbInterface;

   //@RequiresApi(api = Build.VERSION_CODES.N)

   @Override

   public void run()

  {

   try

  {

   for (int i = 0; i < printerDevice.getInterfaceCount(); i++)

  {

  usbInterface = printerDevice.getInterface(i);

  }

   UsbEndpoint endPoint = usbInterface.getEndpoint(0);

  conn = mUsbManager.openDevice(mDevice);

   conn.claimInterface(usbInterface, true);

   //conn.bulkTransfer(endPoint, arregloLogo, arregloLogo.length, 0);

   conn.bulkTransfer(endPoint, arregloBytes, arregloBytes.length, 0);

   mPromise.resolve(arregloBytes.toString());

  mPromise = null;

   conn.close();

  }

   catch (Exception e)

  {

   mPromise.reject(e);

  mPromise = null;

   Log.e("Exception", "Unable to transfer bulk data");

   e.printStackTrace();

  }

  }

  });

  }