在flutter的底部工作表中基于列表创建下拉列表

Question

在我的代码中，我正在解析Json并创建一个Map列表，对于每个Map，我想在下拉列表中显示它们。

这是我的代码

import 'package:flutter/material.dart';

class ReportFilter extends StatefulWidget {
  final Map jsonString;
  var globalData;

  ReportFilter({@required this.jsonString, this.globalData});

  @override
  _ReportFilterState createState() => _ReportFilterState();
}

class _ReportFilterState extends State<ReportFilter> {
  List<TextEditingController> controllers = [];
  TextEditingController controller;
  Map<String, Object> globalValues = Map<String, Object>();

  String type;
  int optionId;

  @override
  void initState() {
    globalValues = widget.globalData;
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Container(
      child: SingleChildScrollView(
          child: Column(
        children: <Widget>[
          Align(
              alignment: Alignment.topRight,
              child: FlatButton.icon(
                label: Text('Filters'),
                icon: Icon(Icons.filter_list),
                onPressed: () => showModalSheet(),
              )),
        ],
      )),
    );
  }

  showModalSheet() {
    List<Map<String, Object>> dropdownList = List<Map<String, Object>>();

       // here I am fetching data from json and doing some operations and storing the result into the List of maps, i.e dropdownList
// below I showed the contents of the dropdownList, and I am passing this list to the Dropdown menu. The contents of the list is dynamic and it keeps changing, It may contains any no of type value as String in  map, or List in map

    showModalBottomSheet<void>(
        shape: RoundedRectangleBorder(
          borderRadius: BorderRadius.circular(10.0),
        ),
        context: context,
        builder: (BuildContext context) {
          return StatefulBuilder(
              builder: (BuildContext context, StateSetter state) {
              return createBox(context, dropdownList, state);

          });
        });
  }

  createBox(BuildContext context, List<Map<String, Object>> val,
      StateSetter setState) {
    Widget supporting = buildSupportingWidget(val, setState);
    return SingleChildScrollView(
        child: LimitedBox(
            maxHeight: 300,
            child: Column(
                mainAxisSize: MainAxisSize.max,
                mainAxisAlignment: MainAxisAlignment.center,
                children: <Widget>[
                  buildMainDropdown(val, setState),
                  if (supporting != null) supporting
                ])));
  }

  Expanded buildMainDropdown(
      List<Map<String, Object>> items, StateSetter setState) {
    return Expanded(
      child: DropdownButtonHideUnderline(
        child: DropdownButton(
          value: type,
          hint: Text("Select a type"),
          items: items
              .map((json) => DropdownMenuItem(
                  child: Text(json["displayName"]), value: json["type"]))
              .toList(),
          onChanged: (newType) {
            setState(() {
              type = newType;
            });
          },
        ),
      ),
    );
  }

  Widget buildSupportingWidget(
      List<Map<String, Object>> items, StateSetter setState) {
    if (type == "list") {
      List<Map<String, Object>> options = items[1]["data"];
      return Expanded(
        child: DropdownButtonHideUnderline(
          child: DropdownButton(
            value: optionId,
            hint: Text("Select an entry"),
            items: options
                .map((option) => DropdownMenuItem(
                    child: Text(option["displayId"]), value: option["id"]))
                .toList(),
            onChanged: (newId) => setState(() {
              this.optionId = newId;
            }),
          ),
        ),
      );
    } else if (type == "string") {
      return Expanded(child: TextFormField());
    }
    return null;
  }
}

在显示模型表中，我正在做一些操作来获取地图列表，  因此，执行完这些后，我的 dropdownList 列表中会包含这样的数据

[
      {
        "displayName": "Enter value",
        "type": "string",
      },
      {
        "displayName": "Enter second value",
        "type": "string",
      },
      {
        "id": "si",
        "displayName": "Source",
        "type": "list",
        "value": ["MO"], "searchField": "si",
        "data": [
          {"id": 1, "displayId": "MO"},
          {"id": 2, "displayId": "AO"},
          {"id": 3, "displayId": "OffNet"}
        ]
      }
    ];

它可以是多个字符串，或者列表取决于我正在处理的Json，

然后，我将列表传递给其中的框，以调用Dropdown函数，但是我没有得到如何基于List创建那些下拉列表的方法，并且一旦用户选择了特定项目，就无法管理最终数据，< / p>

就像如果第一个下拉菜单中的用户选择了一个需要文本框的项目，我需要将输入的值存储在某个地方，并且如果他从第一个下拉列表中选择了导致显示另一个下拉列表的列表，我需要将两个数据都存储在某个地方。 如果有人以前做过这样的事情，或者有人知道这件事，请告诉我，谢谢