app/lib/my_tools/my_datas.dart

import 'dart:convert';

import 'package:bbyyy/beans/commodity_category_bean_entity.dart';
import 'package:bbyyy/https/MyDio.dart';
import 'package:flutter/cupertino.dart';
import 'package:bbyyy/my_tools/event_bus.dart';

class MyData {
  MyData._internal();

  static MyData _singleton = MyData._internal();

  factory MyData() => _singleton;

  List<CommodityCategoryBeanData> commodityCategoryBeanData;

  Future<List<CommodityCategoryBeanData>> getCommodityCategoryBeanData(
      BuildContext context) async {
    if (commodityCategoryBeanData == null) {
      MyDio().query({
        "key": "commodity_category",
        "filters": {},
        "dims": [
          "name",
        ]
      }, (response, hasError) {
        if (!hasError) {
          CommodityCategoryBeanEntity entity = CommodityCategoryBeanEntity()
              .fromJson(json.decode(response.data.toString()));
          commodityCategoryBeanData = entity.data;
          print(json.encode(commodityCategoryBeanData));
          EventBus().emit('commodity_category');
          return commodityCategoryBeanData;
        } else {
          return commodityCategoryBeanData;
        }
      }, (error) {
        return commodityCategoryBeanData;
      });
    } else {
      return commodityCategoryBeanData;
    }
  }

  Future<void> init(BuildContext context) async {
    await getCommodityCategoryBeanData(context);
    EventBus().emit('dataComplete');
  }
}