alertbox.dart

  showDialogBox() => showCupertinoDialog<String>(
        context: context,
        builder: (BuildContext context) => CupertinoAlertDialog(
          title: const Text('No Connection'),
          content: const Text('Please check your internet connectivity'),
          actions: <Widget>[
            TextButton(
              onPressed: () async {
                Navigator.pop(context, 'Cancel');
                setState(() => isAlertSet = false);
                isDeviceConnected =
                    await InternetConnectionChecker().hasConnection;
                if (!isDeviceConnected && isAlertSet == false) {
                  showDialogBox();
                  setState(() => isAlertSet = true);
                }
              },
              child: const Text('OK'),
            ),
          ],
        ),
      );