Future<bool> getLoginStatus() async{
    final prefs = await SharedPreferences.getInstance();
    bool loginStatus = prefs.getBool('login') ?? false;
    print('login status $loginStatus');
    return loginStatus;
  }

  @override
  Widget build(BuildContext context) {
    return FutureBuilder<bool>(
        future: getLoginStatus(),
        builder: (context, snapshot) {
          return (snapshot.data) ?
          // jika sudah login tampilkan list siswa
          new ListSiswa() :
          // jika belum login tampilkan form login
          loginForm();
        },
      );
  }