Flutter : put api response into flutter dropdown menu

I have an API displaying data and I want to put it in the dropdown menu of the flutter app. I can display it in the text but when I try to create a dropdown menu I can't make it yet

so I want to make a dropdown menu from API response like this

{
    "status": "success",
    "message": "Routes Requested !",
    "data": [
        {
            "id": 1,
            "kode_trayek": "603",
            "titik_awal": "Claudia Krajcik V",
            "titik_akhir": "Gust Conn",
            "created_at": "1996-11-01T01:18:26.000000Z",
            "updated_at": "1980-09-18T04:49:44.000000Z",
            "deleted_at": null
        },
        {
            "id": 2,
            "kode_trayek": "539",
            "titik_awal": "Mrs. Tianna Von",
            "titik_akhir": "Anais Dibbert DVM",
            "created_at": "1973-07-04T07:14:05.000000Z",
            "updated_at": "1993-12-11T22:14:31.000000Z",
            "deleted_at": null
        }
    ]
}

and this is an example of my code to fetch data from API

Future<List<Data>> fetchData() async {
  SharedPreferences sharedPreferences = await SharedPreferences.getInstance();
  String? accessToken = sharedPreferences.getString("token");
  final response = await http.get(
    Uri.parse("https://exampleapi.id/api/routes"),
    headers: {
      'Authorization': 'Bearer $accessToken',
    },
  );
  print(response.statusCode);
  print(response.body);
  if (response.statusCode == 200) {
    Map<String, dynamic> map = json.decode(response.body);
    List<dynamic> jsonResponse = map["data"];
    return jsonResponse.map((data) => new Data.fromJson(data)).toList();
  } else {
    throw Exception('Unexpected error occured!');
  }
}

class Data {
  final int id;
  final String titik_awal;
  final String titik_akhir;

  Data({
    required this.id,
    required this.titik_awal,
    required this.titik_akhir,
  });

  factory Data.fromJson(Map<String, dynamic> json) {
    return Data(
      id: json['id'],
      titik_awal: json['titik_awal'],
      titik_akhir: json['titik_akhir'],
    );
  }
}

and in class _RouteState extends State there is this code

late Future<List<Data>> futureData;
  @override
  void initState() {
    super.initState();
    futureData = fetchData();
  }

and here's how I display the data

            FutureBuilder<List<Data>>(
              future: futureData,
              builder: (context, snapshot) {
                if (snapshot.hasData) {
                  List<Data>? data = snapshot.data;
                  return ListView.builder(
                      physics: NeverScrollableScrollPhysics(),
                      scrollDirection: Axis.vertical,
                      shrinkWrap: true,
                      itemCount: data!.length,
                      itemBuilder: (BuildContext context, int index) {
                        return Container(
                          margin: EdgeInsets.only(bottom: 12),
                          child: Column(children: [
                            Text(data[index].id.toString()),
                            Text(data[index].titik_awal),
                            Text(data[index].titik_akhir),
                          ]),
                        );
                      });
                } else if (snapshot.hasError) {
                  return Text("${snapshot.error}");
                }
                // By default show a loading spinner.
                return const CircularProgressIndicator();
              },
            ),

display the data