How I keep data inside BottomSheet Flutter when I close it?

To save data even when closing the BottomSheet is to save user data such as the values the user selected to do that You must save the data in the parent widget if you’re not using any kind of state management like Provider and flutter_bloc, etc
this code will give you a good example of how to do that, then you can use your customization in the code

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Bottom Sheet Demo',
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  List<String> selectedChips = [];
  bool switchValue = false;

  final chipOptions = ['Item 1', 'Item 2', 'Item 3'];

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: ElevatedButton(
          child: Text('Open BottomSheet'),
          onPressed: () {
            showModalBottomSheet(
                context: context,
                builder: (context) {
                  return Column(
                    mainAxisSize: MainAxisSize.min,
                    children: [
                      Wrap(
                        children: chipOptions.map((item) {
                          return ChoiceChip(
                            label: Text(item),
                            selected: selectedChips.contains(item),
                            selectedColor: Colors.green,
                            onSelected: (selected) {
                              setState(() {
                                selected
                                    ? selectedChips.add(item)
                                    : selectedChips.remove(item);
                              });
                            },
                          );
                        }).toList(),
                      ),
                      Switch(
                        value: switchValue,
                        onChanged: (value) {
                          setState(() {
                            switchValue = value;
                          });
                        },
                      ),
                      ElevatedButton(
                        child: Text('Close'),
                        onPressed: () {
                          Navigator.pop(context);
                        },
                      )
                    ],
                  );
                });
          },
        ),
      ),
    );
  }
}

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