<Spinner
        android:id="@+id/spinState"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="10dp"
        android:entries="@array/entry"
         />

private void getCity_State() {
    Call<List<City>> call = AppController.getInstance().getApiInterface().getCity();
    call.enqueue(new Callback<List<City>>() {
        @Override
        public void onResponse(Call<List<City>> call, Response<List<City>> response) {

            if (response.body() != null)
            {
                city = response.body();
                    ArrayList<String> City_States = new ArrayList<>();

                for (int i=0;i<city.size();i++)
                {
                    City_States.add(city.get(i).getCity_name());

                }
                cityType.setAdapter(new ArrayAdapter<String>(SignUpEventActivity.this,android.R.layout.simple_list_item_1,City_States));

            }
        }

        @Override
        public void onFailure(Call<List<City>> call, Throwable t) {

        }
    });
}

public class City {


    @SerializedName("city_name")
    @Expose
    private String city_name;

    @SerializedName("city_id")
    @Expose
    private int city_id;


    public int getCity_id() {
        return city_id;
    }

    public void setCity_id(int city_id) {
        this.city_id = city_id;
    }

    public String getCity_name() {
        return city_name;
    }

    public void setCity_name(String city_name) {
        this.city_name = city_name;
    }


}

@GET("city")
Call<List<City>> getCity();