flutter checkboxlist flutter-showmodalbottomsheet

How to change the value of "CheckboxListTile" widget in "showModalBottomSheet" widget in flutter?

I build an app with flutter,and I want to create page that allow the user to change the value of "CheckboxListTile" widget in "showModalBottomSheet" widget. The "showModalBottomSheet" widget, should be appear after the user click on button.

Here is my code:

class showModalBottomSheetTester extends StatefulWidget {
  const showModalBottomSheetTester({super.key});

  @override
  State<showModalBottomSheetTester> createState() =>
      _showModalBottomSheetTesterState();
}

class _showModalBottomSheetTesterState
    extends State<showModalBottomSheetTester> {
  bool? _isChecked = false;
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('showModalBottomSheetTester'),
      ),
      body: ElevatedButton(
          onPressed: () {
            showModalBottomSheet(
                context: context,
                builder: (BuildContext context) {
                  return SizedBox(
                    height: 500,
                    child: Column(
                      children: [
                        const Padding(
                          padding: EdgeInsets.only(top: 30.0),
                          child: Text('Head'),
                        ),
                        CheckboxListTile(
                            title: const Text('data'),
                            value: _isChecked,
                            activeColor: Colors.red,
                            checkColor: Colors.blue,
                            tileColor: Colors.green,
                            subtitle: const Text('data'),
                            controlAffinity: ListTileControlAffinity.leading,
                            tristate: true,
                            onChanged: (bool? newValue) {
                              setState(() {
                                _isChecked = newValue;
                              });
                            })
                      ],
                    ),
                  );
                });
          },
          child: const Text('press')),
    );
  }
}

The UI of this code is greate, but when I click on the checkbox to change the value, there is no change appear at the screen. H ow to resolve this problem?

Solution

Within a showModalSheet, if you call setState, it won't work. You need to use a StatefulBuilder within the sheet instead.

So wrap the contents of the modalSheet with a StatefulBuilder:

ElevatedButton(
          onPressed: () {
            showModalBottomSheet(
                context: context,
                builder: (BuildContext context) {
                  return StatefulBuilder(
                      builder: (BuildContext context, StateSetter setState) {
                    return SizedBox(
                      height: 500,

Here's a complete runnable snippet:

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Material App',
      home: Scaffold(
        appBar: AppBar(
          title: Text('Material App Bar'),
        ),
        body: Center(child: showModalBottomSheetTester()),
      ),
    );
  }
}

class showModalBottomSheetTester extends StatefulWidget {
  const showModalBottomSheetTester({super.key});

  @override
  State<showModalBottomSheetTester> createState() =>
      _showModalBottomSheetTesterState();
}

class _showModalBottomSheetTesterState
    extends State<showModalBottomSheetTester> {
  bool? _isChecked = false;
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('showModalBottomSheetTester'),
      ),
      body: ElevatedButton(
          onPressed: () {
            showModalBottomSheet(
                context: context,
                builder: (BuildContext context) {
                  return StatefulBuilder(
                      builder: (BuildContext context, StateSetter setState) {
                    return SizedBox(
                      height: 500,
                      child: Column(
                        children: [
                          const Padding(
                            padding: EdgeInsets.only(top: 30.0),
                            child: Text('Head'),
                          ),
                          CheckboxListTile(
                              title: const Text('data'),
                              value: _isChecked,
                              activeColor: Colors.red,
                              checkColor: Colors.blue,
                              tileColor: Colors.green,
                              subtitle: const Text('data'),
                              controlAffinity: ListTileControlAffinity.leading,
                              tristate: true,
                              onChanged: (bool? newValue) {
                                setState(() {
                                  _isChecked = newValue;
                                });
                              })
                        ],
                      ),
                    );
                  });
                });
          },
          child: const Text('press')),
    );
  }
}

See also