Demo doesn't work

[GDN-GR]

Try to build and test the demo but it never execure evt.getSource();

hi.add(new Button(new Command("start scan") {

        @Override
        public void actionPerformed(ActionEvent evt) {
            updateAction("start scan");
            try {
                bt.startScan((ActionListener) evt1 -> {
                            try {
                                JSONObject res = (JSONObject) evt1.getSource();
                                System.out.println("response " + res);
                                updateAction("response " + res);

                                if (res.getString("status").equals("scanResult")) {
                                    //if this is a new device add it
                                    if (!devices.containsKey(res.getString("address"))) {
                                        devices.put(res.getString("address"), res);
                                        updateAction("Dispositivi: " + devices.size());
                                        updateUI();
                                    }
                                }
                            } catch (JSONException ex) {
                                Log.e(ex);
                            }
                        }, null, true, Bluetooth.SCAN_MODE_LOW_POWER, Bluetooth.MATCH_MODE_STICKY,
                        Bluetooth.MATCH_NUM_MAX_ADVERTISEMENT, Bluetooth.CALLBACK_TYPE_ALL_MATCHES);
            }catch (IOException ex) {
                Log.e(ex);
            } 
        }
    }));

How can I get the list of the devices?