我在 Flutter 的多个下拉按钮上保存不同的列表时遇到问题

Question

我是 Flutter 的菜鸟，毕竟是编程。 我正在完成我作为土木工程师毕业的最后一个项目，但我决定编写一个适用于 Android 的应用程序，用于计算用于微桩设计的各种方程。

我已经完成了模拟披萨订单的代码（这对解释变得更加友好），但是我在保存不同列表中的值时遇到问题，这些列表会根据披萨素食或肉类而变化，我仍在努力。

我可以达到这样做的方法或表格，请有人解释或帮助我。

到目前为止的代码：

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';

//Provider
class Datos with ChangeNotifier {
  List _datos = [' '];

  List get datos => _datos;

  set datos(List value){
    _datos = value;
    notifyListeners();
  }

  void goVegan () {
    _datos = [' ','Vegan 1', 'Vegan 2', 'Vegan 3'];
    notifyListeners();
  }

  void goMeat () {
    _datos = [' ', 'Meat 1', 'Meat 2', 'Meat 3'];
    notifyListeners();
  }
}

class lechada extends StatelessWidget {
  // const lechada({Key? key}) : super(key: key);
  int nes = 0;

  @override
  Widget build(BuildContext context) {
    return ChangeNotifierProvider<Datos>(
      create: (context) => Datos(),
      child: Scaffold(
        appBar: AppBar(
          title: const Text('definitivo'),
        ),
        body:Column(
          children: [
            entrada('cantidad de Pizzas'),
            cuerpo(),//nes),
          ],
        ),
      ),
    );
  }
  //inputs de formatos
  entrada(String hint){
    return TextFormField(
      validator: (String? value) { //Esta valida que no este vacio
        if (value == null || value.isEmpty) {
          return 'Campo requerido'; //campo en caso de que este vacio
        }
        return null;
      },
      onSaved: (value) => nes = int.parse(value!),//eje.add(double.parse(value!)), //Aca guarda el valor
      decoration: InputDecoration(
        hintText: hint,
        // icon: Icon(Icons.calendar_view_day_sharp, color: Color(0xFFB14246))
      ),
      keyboardType: TextInputType.number,
    );
  }
}

class cuerpo extends StatefulWidget {
  // const cuerpo({Key? key}) : super(key: key);
  int nes = 3;
  // cuerpo (int nes);
  @override
  State<cuerpo> createState() => _cuerpoState();
}

class _cuerpoState extends State<cuerpo> {
  // List selec = [' ','Pizza Vegan','Pizza Meat'];

  String initial = ' ';
  String initial2 = ' ';

  @override
  Widget build(BuildContext context) {
    final datos = Provider.of<Datos>(context,listen: false);
    return Column(
      children: [
        ListView.builder(
            shrinkWrap: true,
            itemCount: widget.nes ,
            itemBuilder: (BuildContext context, int index) => datosPizza(),
            // {
            //   return datosPizza();
            // },
            ),
        SizedBox(height: 20),
        Container(
          padding: EdgeInsets.all(8),
          child: Text('selec.toString()'),
        ),
        SizedBox(height: 20),
        Row(
          mainAxisAlignment: MainAxisAlignment.spaceAround,
          children: [
            ElevatedButton(onPressed: (){
              setState(() {
                initial = ' ';
                datos.goVegan();
              });
              }, child: Text('Go Vegan')),
            ElevatedButton(onPressed: (){
              setState(() {
                initial = ' ';
                datos.goMeat();
              });
            }, child: Text('Go Meat')),
          ],
        )
      ],
    );
  }
}

class datosPizza extends StatefulWidget {
  // const datosPizza({Key? key}) : super(key: key);

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

class _datosPizzaState extends State<datosPizza> {
  List selec = [' ','Pizza Vegan','Pizza Meat'];

  String initial = ' ';
  String initial2 = ' ';

  @override
  Widget build(BuildContext context) {
    final datos = Provider.of<Datos>(context,listen: false);
    return Row(
      mainAxisAlignment: MainAxisAlignment.spaceAround,
      children: [
        Container(
          padding: EdgeInsets.all(8),
          child: DropdownButton(
              value: initial,
              //Aca recibe los valores y los pasa al map
              items: selec.map((value){ //datos se mete al list
                return DropdownMenuItem(
                  child: new Text(value),
                  value:value,
                );
              }).toList(),
              onChanged: (value) {
                value.toString() == 'Pizza Vegan' ?datos.goVegan() :null;
                value.toString() == 'Pizza Meat' ?datos.goMeat() :null;
                initial2 = ' ';
                setState(() {
                  initial = value.toString();
                });
              })
        ),
        Container(
          padding: EdgeInsets.all(8),
          child: DropdownButton(
              value: initial2,
              //Aca recibe los valores y los pasa al map
              items: datos.datos.map((value){ //datos se mete al list
                return DropdownMenuItem(
                  child: new Text(value),
                  value:value,
                );
              }).toList(),
              onChanged: (value) {
                setState(() {
                  initial2 = value.toString();
                });
              })
        ),
      ],
    );
  }
}

请不要责怪我的英语，我是西班牙裔母语人士

Answer 1

更新：我找到了问题的解决方案，简化是为主要树小部件创建更多的孩子，并继承这些值，所以小部件将保存我们需要的这些值，我将分享代码示例：

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';

//Provider
class Datos with ChangeNotifier {
  List _datos = [' '];
  List guardado = [];
  List gg = [];
  List<String> esgua = [];
  List<double> algua = [];
  List<double> zgua = [];
  // List guardado = [' '];
  int p = 0;

  List get datos => _datos;

  set datos(List value){
    _datos = value;
    notifyListeners();
  }

  void goVegan () {
    _datos = [' ','Vegan 1', 'Vegan 2', 'Vegan 3'];
    // p = 0;
    notifyListeners();
  }

  void goMeat () {
    _datos = [' ', 'Meat 1', 'Meat 2', 'Meat 3'];
    // p = 1;
    notifyListeners();
  }

  void plus () {
    p++;
    notifyListeners();
  }

}

class lechada extends StatelessWidget {
  // const lechada({Key? key}) : super(key: key);
  // int nes = 0;


  @override
  Widget build(BuildContext context) {
    return ChangeNotifierProvider<Datos>(
      create: (context) => Datos(),
      child: Scaffold(
        appBar: AppBar(
          title: const Text('definitivo'),
        ),
        body:Column(
          children: [
            Text('Toma pedido'),
            cuerpo(),
          ],
        ),
      ),
    );
  }
}

class cuerpo extends StatefulWidget {
  // const cuerpo({Key? key}) : super(key: key);

  @override
  State<cuerpo> createState() => _cuerpoState();
}

class _cuerpoState extends State<cuerpo> {
  // List selec = [' ','Pizza Vegan','Pizza Meat'];

  String initial = ' ';
  String initial2 = ' ';
  // GlobalKey<FormState> dkey = GlobalKey<FormState>();


  @override
  Widget build(BuildContext context) {
    final datos = Provider.of<Datos>(context);
    return Column(
      children: [
        ListView.builder(
            shrinkWrap: true,
            itemCount: datos.p,
            itemBuilder: (BuildContext context, int index) => datosPizza(),
            // {
            //   return datosPizza();
            // },
            ),
        SizedBox(height: 20),
        Container(
          padding: EdgeInsets.all(8),
          child: Text('selec.toString()'),
        ),
        SizedBox(height: 20),
        Row(
          mainAxisAlignment: MainAxisAlignment.spaceAround,
          children: [
            ElevatedButton(
                onPressed: (){
                  setState(() {
                    print (datos.gg);
                    datos.p!=datos.gg.length
                        ?print ('error')
                        :null;
              });
              }, child: Text('Print')
            ),
            ElevatedButton(
                onPressed: (){
                  datos.p = 0;
                  datos.gg.clear();
                },
                child: Text('Reinicia')),
            ElevatedButton(
                onPressed: (){
                  datos.plus();
                },
                child: Text('Add estrato')
            ),
          ],
        )
      ],
    );
  }
}

class datosPizza extends StatefulWidget {
  const datosPizza({Key? key}) : super(key: key);

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

class _datosPizzaState extends State<datosPizza> {
  List selec = [' ','Pizza Vegan','Pizza Meat'];

  String initial = ' ';
  String initial2 = ' ';
  List temp = [];
  List<double> eje = [];
  

  @override
  Widget build(BuildContext context) {
    final datos = Provider.of<Datos>(context,listen: false);
    return Row(
      mainAxisAlignment: MainAxisAlignment.spaceAround,
      children: [
        Container(
          width: 150,
          padding: EdgeInsets.all(8),
          child: DropdownButton(
              value: initial,
              //Aca recibe los valores y los pasa al map
              items: selec.map((value){ //datos se mete al list
                return DropdownMenuItem(
                  child: new Text(value),
                  value:value,
                );
              }).toList(),

              onChanged: (value) {
                value.toString() == 'Pizza Vegan' ?datos.goVegan() :null;
                value.toString() == 'Pizza Meat' ?datos.goMeat() :null;
                initial2 = ' ';
                temp.addAll(datos._datos); //Añade los datos de entrada y los pasa al widget para que los conserve
                setState(() {
                  initial = value.toString();
                });
              })
        ),
        Container(
          width: 100,
          padding: EdgeInsets.all(8),
          child: dropdowBut(temp),
        ),
        Container(
          width: 70,
          padding: EdgeInsets.all(8),
          child: entrada('mts'),
        )
      ],
    );
  }
  //inputs de formatos
  entrada(String hint){
    return TextFormField(
      validator: (String? value) { //Esta valida que no este vacio
        if (value == null || value.isEmpty) {
          return 'Campo requerido'; //campo en caso de que este vacio
        }
        return null;
      },
      onSaved: (value) => eje.add(double.parse(value!)),//eje.add(double.parse(value!)), //Aca guarda el valor
      onFieldSubmitted: (value) => print(value),
      // onChanged: (value)=> print(value),
      decoration: InputDecoration(
        hintText: hint,
        // icon: Icon(Icons.calendar_view_day_sharp, color: Color(0xFFB14246))
      ),
      keyboardType: TextInputType.number,
    );
  }
}

class dropdowBut extends StatefulWidget {
  // const dropdowBut({Key? key}) : super(key: key);
  String initial2 =' ';
  List temp ;


  dropdowBut(this.temp);


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

class _dropdowButState extends State<dropdowBut> {
  String _value = ' ';

  @override
  Widget build(BuildContext context) {
    final datos = Provider.of<Datos>(context,listen: false);
    return DropdownButton(
        // value: widget.initial2,
        value: _value,
        // hint: Text('hi'),
        //Aca recibe los valores y los pasa al map
        items:
        widget.temp.map((value){ //datos se mete al list
          return DropdownMenuItem(
            child: new Text(value),
            value:value,
          );
        }).toList(),
        onChanged: (value) {
          datos.gg.add(value);
          setState(() {
            _value = value.toString();
          });
        });
  }
}

对不起，如果我纠结了代码，但我还在学习 Flutter。