【Flutter】アラートを出す（ノーマルとiOS風）

AlertDialog _alertBuilder( BuildContext context,  String msg ) {
    return AlertDialog(
      title: const Text('My App'),
      content: Text(msg),
      actions: [
        TextButton(
          onPressed: () {
            Navigator.pop(context, 'OK');
          },
         child: const Text('OK'))
      ],);
  }

  CupertinoAlertDialog _alertBuilderForCupertino( BuildContext context, String msg ) {

    return CupertinoAlertDialog(
      title: const Text('My App (like iOS)'),
      content: Text(msg),
      actions: [
        CupertinoDialogAction(child: const Text('OK'), onPressed: () {
          Navigator.pop(context);
        },)
      ],
    );
  }

  void _showAlert( String msg) {
    showDialog(
      context: context,
      builder: (BuildContext context) => _alertBuilder( context, msg ) );
  }