Flutter：如何从运行时创建的列表中访问单个子部件的值

在这里，我举了一个例子，说明如何使用您已经使用过的Provider个包来实现它，这样您就可以根据您的需要进行调整. 以下是UserVariablesModel提供程序示例:

import 'package:flutter/material.dart';

class UserVariablesModel with ChangeNotifier {
  final List<SliderVariable> _userVariables = [
    SliderVariable(min: 0, max: 10, question: 'How would you rate your sleep?'),
    SliderVariable(
        min: 0,
        max: 10,
        question: 'How many times did you wake up in the night?'),
  ];

  List<SliderVariable> get userVariables => List.unmodifiable(_userVariables);

  updateVariable(SliderVariable sliderVariable, double value) {
    final index = userVariables.indexOf(sliderVariable);
    if (index != -1) {
      _userVariables[index] = sliderVariable.copyWith(value: value);
      notifyListeners();
    }
  }
}

class SliderVariable {
  double min;
  double max;
  double value;
  String question;

  SliderVariable({
    required this.min,
    required this.max,
    double? value,
    required this.question,
  }) : value = value ?? min;

  SliderVariable copyWith({
    double? min,
    double? max,
    double? value,
    String? question,
  }) {
    return SliderVariable(
      min: min ?? this.min,
      max: max ?? this.max,
      value: value ?? this.value,
      question: question ?? this.question,
    );
  }
}

这是如何使用它来反映变化的示例:

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:test/business/user_variables_model.dart';

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

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return ChangeNotifierProvider(
      create: (context) => UserVariablesModel(),
      child: const MaterialApp(
        home: Scaffold(
          body: SafeArea(
            child: MorningSurveyScreen(),
          ),
        ),
      ),
    );
  }
}

class MorningSurveyScreen extends StatelessWidget {
  const MorningSurveyScreen({Key? key}) : super(key: key);

  Future<void> _addEntry(List<SliderVariable> sliderVariables) async {
    print("slider values:");
    for (var userVariable in sliderVariables) {
      print(userVariable.value);
    }

    // bool addEntry = await DialogHelper.showAddEntryDialog(context);
    // if (addEntry) {
    //   await CsvDataService.addRowToCsv({
    //     // THIS POINT IS WHERE I NEED TO ACCESS THE SLIDER VALUES
    //   });
    // }
  }

  @override
  Widget build(BuildContext context) {
    //wrap in consumer
    return Consumer<UserVariablesModel>(
      builder: (context, userVariablesModel, child) => Stack(
        children: [
          Center(
            child: ListView(
              children: <Widget>[
                // OTHER WIDGETS,
                for (var sliderVariable in userVariablesModel.userVariables)
                  SliderWidget(sliderVariable: sliderVariable)
              ],
            ),
          ),
          Positioned(
            bottom: 16,
            right: 16,
            child: FloatingActionButton(
              onPressed: () => _addEntry(userVariablesModel.userVariables),
              tooltip: 'Add entry',
              child: const Icon(Icons.check),
            ),
          )
        ],
      ),
    );
  }
}

class SliderWidget extends StatelessWidget {
  final SliderVariable sliderVariable;

  const SliderWidget({Key? key, required this.sliderVariable})
      : super(key: key);

  @override
  Widget build(BuildContext context) {
    final currentSliderValue = sliderVariable.value.toDouble();
    return Column(
      children: [
        // OTHER WIDGETS,
        Slider(
          value: currentSliderValue,
          min: sliderVariable.min.toDouble(),
          max: sliderVariable.max.toDouble(),
          divisions: (sliderVariable.max - sliderVariable.min).toInt(),
          label: currentSliderValue.round().toString(),
          onChanged: (double value) {
            Provider.of<UserVariablesModel>(context, listen: false)
                .updateVariable(sliderVariable, value);
          },
        )
      ],
    );
  }
}