小编Ant*_*ono的帖子

尝试使用对象模型从我的API JSON添加元素时收到以下错误 DropdownMenuItem

这是错误：

The method 'map' was called on null.
Receiver: null
Tried calling: map<DropdownMenuItem<Provinces>>(Closure: (Provinces) => DropdownMenuItem<Provinces>)

这是我的飞镖代码：

import 'dart:async';

import 'dart:convert';
import 'package:flutter/material.dart';
import 'package:sj/utils/constants.dart';
import 'package:http/http.dart' as http;
import 'package:sj/models/master/provinces.dart';

class IdCardFormPage extends StatefulWidget {
  @override
  _IdCardFormPageState createState() => new _IdCardFormPageState();
}

class _IdCardFormPageState extends State<IdCardFormPage> {

  List<Provinces> listProvinces;
  Provinces _selectedProvince;

  Future<List<Provinces>> getProvinceList() async {
    //final response = await http.get("${APIConstants.API_BASE_URL}api/masters/provincesList.php");
    final response = await http.get("url");

    listProvinces = parseProvinces(response.body);

    return parseProvinces(response.body);
  }

  List<Provinces> parseProvinces(String responseBody) {
    final …