获取Firebase设备令牌android delphi 10.2

Question

我正在按照本教程http://thundaxsoftware.blogspot.com/2017/01/firebase-cloud-messaging-with-delphi.html使用推送通知，

 {$IFDEF ANDROID}
   PushService := TPushServiceManager.Instance.GetServiceByName(TPushService.TServiceNames.GCM);
  PushService.AppProps[TPushService.TAppPropNames.GCMAppID] := '71553856XXXX';
{$ENDIF}
  ServiceConnection := TPushServiceConnection.Create(PushService);
  //ServiceConnection.Active := True; //Update
  ServiceConnection.OnChange := OnServiceConnectionChange;
  ServiceConnection.OnReceiveNotification := OnReceiveNotificationEvent;
  ServiceConnection.Active := True; 

  DeviceId := PushService.DeviceIDValue[TPushService.TDeviceIDNames.DeviceId];
  DeviceToken := PushService.DeviceTokenValue[TPushService.TDeviceTokenNames.DeviceToken];
  Memo1.Lines.Add(DateTimeToStr(Now) + ' DeviceID: ' + DeviceId);
  Memo1.Lines.Add(DateTimeToStr(Now) + ' FCM Token: ' + DeviceToken);
  Memo1.Lines.Add(DateTimeToStr(Now) + ' Ready to receive!');

值DeviceToken为空！但是显示了设备ID，我使用的是与本文所附的源代码相同的代码。