Checkbox doesn't change when clicked in dropdownbutton - flutter

Question

I am using DropdownButton and I am facing the following issue. I'm using a checkbox in elements, but when I click on an element, I don't get a checkmark indicating that the checkbox has been clicked. As a result, I need to close and reopen it, and then I will see the changes that were clicked on the "checkbox". The second problem is that when I select one element, all elements are selected for me. As a final result, I need to get so that I can select an element and the checkbox is immediately marked, if 2 elements are needed, then two, and so on. Tell me how to fix these problems, I will be grateful for the help?
dropdown
class DropdownWidget extends StatefulWidget {
List<String> items;
SvgPicture? icon;
double width;
DropdownWidget({
Key? key,
required this.items,
required this.icon,
required this.width,
}) : super(key: key);
#override
State<DropdownWidget> createState() => _DropdownWidgetState();
}
class _DropdownWidgetState extends State<DropdownWidget> {
String? selectedValue;
bool isChecked = false;
#override
void initState() {
super.initState();
if (widget.items.isNotEmpty) {
selectedValue = widget.items[1];
}
}
#override
Widget build(BuildContext context) {
return SizedBox(
width: widget.width,
child: DropdownButtonHideUnderline(
child: DropdownButton2(
items: widget.items
.map((item) => DropdownMenuItem<String>(
value: item,
child: Container(
decoration: BoxDecoration(
border: Border(
bottom: BorderSide(
color: constants.Colors.white.withOpacity(0.1),
width: 1,
),
),
),
child: Center(
child: Row(
children: [
if (item == selectedValue)
const SizedBox(
width: 0,
),
Expanded(
child: Text(
item,
style: constants.Styles.smallTextStyleWhite,
),
),
Checkbox(
checkColor: Colors.black,
value: isChecked,
onChanged: (bool? value) {
setState(() {
isChecked = value!;
});
},
),
],
),
),
),
))
.toList(),
value: selectedValue,
onChanged: (value) {
setState(() {
selectedValue = value as String;
});
},
icon: SvgPicture.asset(constants.Assets.arrowDropdown),
iconSize: 21,
buttonHeight: 27,
itemHeight: 47,
dropdownMaxHeight: 191,
dropdownWidth: 140,
dropdownDecoration: BoxDecoration(
borderRadius: BorderRadius.circular(8),
border: Border.all(
color: constants.Colors.purpleMain,
),
color: constants.Colors.greyDark,
),
selectedItemBuilder: (context) {
return widget.items.map(
(item) {
return Row(
children: [
widget.icon ?? const SizedBox(),
const SizedBox(width: 8),
Text(
item,
style: constants.Styles.bigBookTextStyleWhite,
),
],
);
},
).toList();
},
),
),
);
}
}
items
final List<String> items = const [
"All EV's",
'Main EV',
'<EV2>',
];

Answer 1

I hope this example explains the concept. For simplcity I made simple a new file, run it and see the results:
Then main idea in two lists, _checkList contain values of the CheckBox and _selectedList handles the main dropdown widget to show the selection.
Feel free to ask any questions and I'm happy to help
import 'package:flutter/material.dart';
class TestPage extends StatelessWidget {
const TestPage({Key? key}) : super(key: key);
#override
Widget build(BuildContext context) {
return const AnimationDemo(number: 5);
}
}
class AnimationDemo extends StatefulWidget {
const AnimationDemo({Key? key, this.number = 2}) : super(key: key);
final int number;
#override
State<AnimationDemo> createState() => _AnimationDemoState();
}
class _AnimationDemoState extends State<AnimationDemo> {
late List<bool> _checkList;
late List<int> _selectedIndex;
bool _isOpen = false;
#override
void initState() {
_checkList = List.filled(widget.number, false);
_selectedIndex = <int>[];
super.initState();
}
List<DropDownItem> generateItems() {
var tmp = <DropDownItem>[];
for (var i = 0; i < _checkList.length; i++) {
tmp.add(DropDownItem(
isChecked: _checkList[i],
onChanged: (value) {
setState(() {
_checkList[i] = value!;
if (value && !_selectedIndex.contains(i)) {
_selectedIndex.add(i);
} else {
_selectedIndex.remove(i);
}
});
},
));
}
return tmp;
}
#override
Widget build(BuildContext context) {
return SafeArea(
child: Column(
mainAxisAlignment: MainAxisAlignment.start,
mainAxisSize: MainAxisSize.min,
children: [
Row(
children: [
Expanded(
child: Text((_selectedIndex.isEmpty)
? 'Nothing Selected'
: _selectedIndex.join(',')),
),
GestureDetector(
onTap: () {
setState(() {
_isOpen = !_isOpen;
});
},
child: const Icon(Icons.arrow_downward),
),
],
),
AnimatedOpacity(
opacity: (_isOpen) ? 1 : 0,
duration: const Duration(milliseconds: 300),
child: Column(
mainAxisSize: MainAxisSize.min,
children: generateItems(),
),
)
],
),
);
}
}
class DropDownItem extends StatelessWidget {
final bool isChecked;
final Function(bool?)? onChanged;
const DropDownItem({Key? key, this.onChanged, this.isChecked = false})
: super(key: key);
#override
Widget build(BuildContext context) {
return Row(
children: [
const Expanded(child: Text('Demo item')),
Checkbox(value: isChecked, onChanged: onChanged)
],
);
}
}

Answer 2

Here's how to achieve the Multiselect dropdown with DropdownButton2:
final List<String> items = [
'Item1',
'Item2',
'Item3',
'Item4',
];
List<String> selectedItems = [];
#override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: DropdownButtonHideUnderline(
child: DropdownButton2(
isExpanded: true,
hint: Align(
alignment: AlignmentDirectional.center,
child: Text(
'Select Items',
style: TextStyle(
fontSize: 14,
color: Theme.of(context).hintColor,
),
),
),
items: items.map((item) {
return DropdownMenuItem<String>(
value: item,
//disable default onTap to avoid closing menu when selecting an item
enabled: false,
child: StatefulBuilder(
builder: (context, menuSetState) {
final _isSelected = selectedItems.contains(item);
return InkWell(
onTap: () {
_isSelected
? selectedItems.remove(item)
: selectedItems.add(item);
//This rebuilds the StatefulWidget to update the button's text
setState(() {});
//This rebuilds the dropdownMenu Widget to update the check mark
menuSetState(() {});
},
child: Container(
height: double.infinity,
padding: const EdgeInsets.symmetric(horizontal: 16.0),
child: Row(
children: [
_isSelected
? const Icon(Icons.check_box_outlined)
: const Icon(Icons.check_box_outline_blank),
const SizedBox(width: 16),
Text(
item,
style: const TextStyle(
fontSize: 14,
),
),
],
),
),
);
},
),
);
}).toList(),
//Use last selected item as the current value so if we've limited menu height, it scroll to last item.
value: selectedItems.isEmpty ? null : selectedItems.last,
onChanged: (value) {},
buttonHeight: 40,
buttonWidth: 140,
itemHeight: 40,
itemPadding: EdgeInsets.zero,
selectedItemBuilder: (context) {
return items.map(
(item) {
return Container(
alignment: AlignmentDirectional.center,
padding: const EdgeInsets.symmetric(horizontal: 16.0),
child: Text(
selectedItems.join(', '),
style: const TextStyle(
fontSize: 14,
overflow: TextOverflow.ellipsis,
),
maxLines: 1,
),
);
},
).toList();
},
),
),
),
);
}
Also, I've added it as an example to the package doc "Example 4" so you can get back to it later.