当其他下拉值在颤振中更改时，将下拉值重置为偏移量0

如何解决当其他下拉值在颤振中更改时，将下拉值重置为偏移量0

我正在使用一个下拉小部件来显示其中的多个drpdown。

  String CountryVal,StateVal;
  Widget _dropdown(List<String> _options,String selected){
    return Container(
      padding: EdgeInsets.fromLTRB(15.0,4.0,15.0,4.0),margin: EdgeInsets.fromLTRB(20.0,7.0,20.0,10.0),child: DropdownButtonHideUnderline(
        child: DropdownButton<String>(
          isExpanded: true,hint: Text(
            _options[0],style: TextStyle(
              color: Colors.blue,fontSize: 18.0,),items: _options.map((String value){
            return DropdownMenuItem<String>(
              value: value,child: Text(value),);
          }).toList(),onChanged: (String captureSelected) {
            setState(() {
              if(selected == 'Country Dropdown'){
                  CountryVal = captureSelected;
              } else if(selected == 'State Dropdown'){
                  StateVal = captureSelected;
              }
            });
          },value: selected == 'Country Dropdown' ? CountryVal : StateVal,style: TextStyle(
            color: Colors.blue,);
  }

我已经多次使用它进行不同的下拉菜单

List<String> _country = ['- Select Country -','USA','UK'];
List<String> _state = ['- Select State -','New York','London'];
_dropdown(_country,'Country Dropdown');
_dropdown(_state,'State Dropdown');

现在接通“状态下拉”值取决于“国家下拉”，我需要重置“状态下拉”的值来抵消0当选择“国家下拉”值。

我已经花费了数小时进行搜索并亲自尝试，但是可以正确完成。请帮忙。

解决方法

您可以在下面复制粘贴运行完整代码
您可以在选择“国家/地区”下拉菜单值时设置StateVal = _state[0];。
代码段

if (selected == 'Country Dropdown') {
        CountryVal = captureSelected;
        StateVal = _state[0];
      }

工作演示

完整代码

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',theme: ThemeData(
        primarySwatch: Colors.blue,visualDensity: VisualDensity.adaptivePlatformDensity,),home: MyHomePage(title: 'Flutter Demo Home Page'),);
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key,this.title}) : super(key: key);

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  String CountryVal,StateVal;
  List<String> _country = ['- Select Country -','USA','UK'];
  List<String> _state = ['- Select State -','New York','London'];

  Widget _dropdown(List<String> _options,String selected) {
    return Container(
      padding: EdgeInsets.fromLTRB(15.0,4.0,15.0,4.0),margin: EdgeInsets.fromLTRB(20.0,7.0,20.0,10.0),child: DropdownButtonHideUnderline(
        child: DropdownButton<String>(
          isExpanded: true,hint: Text(
            _options[0],style: TextStyle(
              color: Colors.blue,fontSize: 18.0,items: _options.map((String value) {
            return DropdownMenuItem<String>(
              value: value,child: Text(value),);
          }).toList(),onChanged: (String captureSelected) {
            setState(() {
              if (selected == 'Country Dropdown') {
                CountryVal = captureSelected;
                StateVal = _state[0];
              } else if (selected == 'State Dropdown') {
                StateVal = captureSelected;
              }
            });
          },value: selected == 'Country Dropdown' ? CountryVal : StateVal,style: TextStyle(
            color: Colors.blue,);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,children: <Widget>[
            _dropdown(_country,'Country Dropdown'),_dropdown(_state,'State Dropdown')
          ],);
  }
}