Flutter DropdownButton2

Intro

Flutter's core Dropdown Button widget with steady dropdown menu and many other options you can customize to your needs.

• Features
• Options
• Installation
• Usage and Examples
  • 1. Simple DropdownButton2 with no styling
  • 2. DropdownButton2 with some styling and customization
  • 3. DropdownButton2 with items of different heights like dividers
  • 4. DropdownButton2 as Multiselect Dropdown with Checkboxes
  • 5. DropdownButton2 as Searchable Dropdown
  • 6. DropdownButton2 as Popup menu button using customButton parameter
  • 7. Using DropdownButtonFormField2 with Form
• CustomDropdownButton2 Widget "customize it to your needs"

Features

• Dropdown menu always open below the button "as long as it's possible otherwise it'll open to the end of the screen" and you can edit its position by using the offset parameter.
• You can control how (button, button's icon, dropdown menu and menu items) will be displayed "read Options below".
• You can align (hint & value) and customize them.
• You can edit the scrollbar's radius,thickness and isAlwaysShow.
• You can set max height for the dropdown menu & it'll become scrollable if there are more items.
• If you pass Null to dropdownMaxHeight parameter or didn't use it, the dropdown menu will take max height possible for the items and will become scrollable if there are more items.
• If you have long scrollable list, the dropdown menu will auto scroll to current selected item and show it at the middle of the menu if possible.
• Wrap DropdownButton2 with DropdownButtonHideUnderline to hide the underline.
• A Custom widget of the DropdownButton2 below to make it more reusable. You can customize it to your needs and use it throughout all your app easily as shown in the examples.
• You can use DropdownButton2 with items of different heights like dividers as shown in the examples.
• You can use DropdownButton2 as Multiselect Dropdown with Checkboxes as shown in the examples.
• You can use DropdownButton2 as Searchable Dropdown as shown in the examples.
• You can use DropdownButton2 as a popup menu button by using the parameter customButton. You can pass Icon,Image or any widget and customize it as shown in the examples.
• You can also use DropdownButtonFormField2 the same way with all options above and use it inside Form as shown in the examples.
• Use decoration parameter for the DropdownButtonFormField2 to add borders, label and more.
• You can customize DropdownButtonFormField2 width by wrapping it with Padding or with SizedBox and give it the width you want.

Options

For DropdownButton2:

Option	Description	Type	Required
items	The list of items the user can select	List<DropdownMenuItem>	Yes
hint	The placeholder displayed before the user choose an item	Widget	No
disabledHint	The placeholder displayed if the dropdown is disabled	Widget	No
value	The value of the currently selected [DropdownMenuItem]	T	No
onChanged	Called when the user selects an item	ValueChanged<T?>	No
onMenuStateChange	Called when the dropdown menu is opened or closed	Function(bool isOpen)	No
selectedItemBuilder	How the selected item will be displayed on button	DropdownButtonBuilder	No
buttonHeight	The height of the button	double	No
buttonWidth	The width of the button	double	No
buttonPadding	The inner padding of the Button	EdgeInsetsGeometry	No
buttonDecoration	The decoration of the Button	BoxDecoration	No
buttonElevation	The elevation of the Button	int	No
buttonSplashColor	The splash color of the button's InkWell	Color	No
buttonHighlightColor	The highlight color of the button's InkWell	Color	No
buttonOverlayColor	The overlay color of the button's InkWell	MaterialStateProperty<Color?>	No
icon	The suffix icon of the dropdown button	Widget	No
iconOnClick	Shows different icon when dropdown menu open	Widget	No
iconSize	The size of the icon	double	No
iconEnabledColor	The color of the icon if the button is enabled	Color	No
iconDisabledColor	The color of the icon if the button is disabled	Color	No
itemHeight	The height of menu items	double	No
itemPadding	The padding of menu items	EdgeInsetsGeometry	No
itemSplashColor	The splash color of the item's InkWell	Color	No
itemHighlightColor	The highlight color of the item's InkWell	Color	No
dropdownMaxHeight	The maximum height of the dropdown menu	double	No
dropdownWidth	The width of the dropdown menu	double	No
dropdownPadding	The inner padding of the dropdown menu	EdgeInsetsGeometry	No
dropdownScrollPadding	The inner padding of the dropdown menu including the scrollbar	EdgeInsetsGeometry	No
dropdownDecoration	The decoration of the dropdown menu	BoxDecoration	No
dropdownDirection	The direction of the dropdown menu in relation to the button	DropdownDirection	No
dropdownElevation	The elevation of the dropdown menu	int	No
selectedItemHighlightColor	The highlight color of the current selected item	Color	No
scrollbarRadius	The radius of the scrollbar's corners	Radius	No
scrollbarThickness	The thickness of the scrollbar	double	No
scrollbarAlwaysShow	Always show the scrollbar even when a scroll is not underway	bool	No
offset	Changes the position of the dropdown menu	Offset	No
customButton	Uses custom widget like icon,image,etc.. instead of the default button	Widget	No
customItemsHeights	Uses different predefined heights for the menu items (useful for adding dividers)	List	No
isExpanded	Makes the button's inner contents expanded (set true to avoid long text overflowing)	bool	No
openWithLongPress	Opens the dropdown menu on long-pressing instead of tapping	bool	No
dropdownOverButton	Opens the dropdown menu over the button instead of below it	bool	No
dropdownFullScreen	Opens the dropdown menu in fullscreen mode (Above AppBar & TabBar)	bool	No
focusColor	The color of button when it has input focus using traditional interfaces (keyboard and mouse)	Color	No
barrierDismissible	Whether you can dismiss this route by tapping the modal barrier	bool	No
barrierColor	The color to use for the modal barrier. If this is null, the barrier will be transparent	Color	No
barrierLabel	The semantic label used for a dismissible barrier	String	No
searchController	The controller used for searchable dropdowns, if null, then it'll perform as a normal dropdown	TextEditingController	No
searchInnerWidget	The widget to be shown at the top of the dropdown menu for searchable dropdowns	Widget	No
searchMatchFn	The match function used for searchable dropdowns, if null, defaultFn will be used	SearchMatchFn	No

For DropdownButtonFormField2 "In addition to the above":

Option	Description	Type	Required
dropdownButtonKey	The key of DropdownButton2 child widget	Key	No
decoration	The decoration of the dropdown button form field	InputDecoration	No
onSaved	Called with the current selected item when the form is saved	FormFieldSetter	No
validator	Called to validates if the input is invalid and display error text	FormFieldValidator	No
autovalidateMode	Used to enable/disable auto validation	AutovalidateMode	No

Installation

add this line to pubspec.yaml

dependencies:

  dropdown_button2: ^1.9.2

import package

import 'package:dropdown_button2/dropdown_button2.dart';

Usage and Examples

1. Simple DropdownButton2 with no styling:

final List<String> items = [
  'Item1',
  'Item2',
  'Item3',
  'Item4',
];
String? selectedValue;

@override
Widget build(BuildContext context) {
  return Scaffold(
    body: Center(
      child: DropdownButtonHideUnderline(
        child: DropdownButton2(
          hint: Text(
            'Select Item',
            style: TextStyle(
              fontSize: 14,
              color: Theme
                      .of(context)
                      .hintColor,
            ),
          ),
          items: items
                  .map((item) =>
                  DropdownMenuItem<String>(
                    value: item,
                    child: Text(
                      item,
                      style: const TextStyle(
                        fontSize: 14,
                      ),
                    ),
                  ))
                  .toList(),
          value: selectedValue,
          onChanged: (value) {
            setState(() {
              selectedValue = value as String;
            });
          },
          buttonHeight: 40,
          buttonWidth: 140,
          itemHeight: 40,
        ),
      ),
    ),
  );
}

2. DropdownButton2 with some styling and customization:

final List<String> items = [
  'Item1',
  'Item2',
  'Item3',
  'Item4',
  'Item5',
  'Item6',
  'Item7',
  'Item8',
];
String? selectedValue;

@override
Widget build(BuildContext context) {
  return Scaffold(
    body: Center(
      child: DropdownButtonHideUnderline(
        child: DropdownButton2(
          isExpanded: true,
          hint: Row(
            children: const [
              Icon(
                Icons.list,
                size: 16,
                color: Colors.yellow,
              ),
              SizedBox(
                width: 4,
              ),
              Expanded(
                child: Text(
                  'Select Item',
                  style: TextStyle(
                    fontSize: 14,
                    fontWeight: FontWeight.bold,
                    color: Colors.yellow,
                  ),
                  overflow: TextOverflow.ellipsis,
                ),
              ),
            ],
          ),
          items: items
                  .map((item) =>
                  DropdownMenuItem<String>(
                    value: item,
                    child: Text(
                      item,
                      style: const TextStyle(
                        fontSize: 14,
                        fontWeight: FontWeight.bold,
                        color: Colors.white,
                      ),
                      overflow: TextOverflow.ellipsis,
                    ),
                  ))
                  .toList(),
          value: selectedValue,
          onChanged: (value) {
            setState(() {
              selectedValue = value as String;
            });
          },
          icon: const Icon(
            Icons.arrow_forward_ios_outlined,
          ),
          iconSize: 14,
          iconEnabledColor: Colors.yellow,
          iconDisabledColor: Colors.grey,
          buttonHeight: 50,
          buttonWidth: 160,
          buttonPadding: const EdgeInsets.only(left: 14, right: 14),
          buttonDecoration: BoxDecoration(
            borderRadius: BorderRadius.circular(14),
            border: Border.all(
              color: Colors.black26,
            ),
            color: Colors.redAccent,
          ),
          buttonElevation: 2,
          itemHeight: 40,
          itemPadding: const EdgeInsets.only(left: 14, right: 14),
          dropdownMaxHeight: 200,
          dropdownWidth: 200,
          dropdownPadding: null,
          dropdownDecoration: BoxDecoration(
            borderRadius: BorderRadius.circular(14),
            color: Colors.redAccent,
          ),
          dropdownElevation: 8,
          scrollbarRadius: const Radius.circular(40),
          scrollbarThickness: 6,
          scrollbarAlwaysShow: true,
          offset: const Offset(-20, 0),
        ),
      ),
    ),
  );
}

3. DropdownButton2 with items of different heights like dividers:

  final List<String> items = [
  'Item1',
  'Item2',
  'Item3',
  'Item4',
];
String? selectedValue;

List<DropdownMenuItem<String>> _addDividersAfterItems(List<String> items) {
  List<DropdownMenuItem<String>> _menuItems = [];
  for (var item in items) {
    _menuItems.addAll(
      [
        DropdownMenuItem<String>(
          value: item,
          child: Padding(
            padding: const EdgeInsets.symmetric(horizontal: 8.0),
            child: Text(
              item,
              style: const TextStyle(
                fontSize: 14,
              ),
            ),
          ),
        ),
        //If it's last item, we will not add Divider after it.
        if (item != items.last)
          const DropdownMenuItem<String>(
            enabled: false,
            child: Divider(),
          ),
      ],
    );
  }
  return _menuItems;
}

List<double> _getCustomItemsHeights() {
  List<double> _itemsHeights = [];
  for (var i = 0; i < (items.length * 2) - 1; i++) {
    if (i.isEven) {
      _itemsHeights.add(40);
    }
    //Dividers indexes will be the odd indexes
    if (i.isOdd) {
      _itemsHeights.add(4);
    }
  }
  return _itemsHeights;
}

@override
Widget build(BuildContext context) {
  return Scaffold(
    body: Center(
      child: DropdownButtonHideUnderline(
        child: DropdownButton2(
          isExpanded: true,
          hint: Text(
            'Select Item',
            style: TextStyle(
              fontSize: 14,
              color: Theme.of(context).hintColor,
            ),
          ),
          items: _addDividersAfterItems(items),
          customItemsHeights: _getCustomItemsHeights(),
          value: selectedValue,
          onChanged: (value) {
            setState(() {
              selectedValue = value as String;
            });
          },
          buttonHeight: 40,
          dropdownMaxHeight: 200,
          buttonWidth: 140,
          itemPadding: const EdgeInsets.symmetric(horizontal: 8.0),
        ),
      ),
    ),
  );
}

4. DropdownButton2 as Multiselect Dropdown with Checkboxes:

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();
          },
        ),
      ),
    ),
  );
}

5. DropdownButton2 as Searchable Dropdown:

final List<String> items = [
  'A_Item1',
  'A_Item2',
  'A_Item3',
  'A_Item4',
  'B_Item1',
  'B_Item2',
  'B_Item3',
  'B_Item4',
];

String? selectedValue;
final TextEditingController textEditingController = TextEditingController();

@override
void dispose() {
  textEditingController.dispose();
  super.dispose();
}

@override
Widget build(BuildContext context) {
  return Scaffold(
    body: Center(
      child: DropdownButtonHideUnderline(
        child: DropdownButton2(
          isExpanded: true,
          hint: Text(
            'Select Item',
            style: TextStyle(
              fontSize: 14,
              color: Theme.of(context).hintColor,
            ),
          ),
          items: items
                  .map((item) => DropdownMenuItem<String>(
            value: item,
            child: Text(
              item,
              style: const TextStyle(
                fontSize: 14,
              ),
            ),
          ))
                  .toList(),
          value: selectedValue,
          onChanged: (value) {
            setState(() {
              selectedValue = value as String;
            });
          },
          buttonHeight: 40,
          buttonWidth: 200,
          itemHeight: 40,
          dropdownMaxHeight: 200,
          searchController: textEditingController,
          searchInnerWidget: Padding(
            padding: const EdgeInsets.only(
              top: 8,
              bottom: 4,
              right: 8,
              left: 8,
            ),
            child: TextFormField(
              controller: textEditingController,
              decoration: InputDecoration(
                isDense: true,
                contentPadding: const EdgeInsets.symmetric(
                  horizontal: 10,
                  vertical: 8,
                ),
                hintText: 'Search for an item...',
                hintStyle: const TextStyle(fontSize: 12),
                border: OutlineInputBorder(
                  borderRadius: BorderRadius.circular(8),
                ),
              ),
            ),
          ),
          searchMatchFn: (item, searchValue) {
            return (item.value.toString().contains(searchValue));
          },
          //This to clear the search value when you close the menu
          onMenuStateChange: (isOpen) {
            if (!isOpen) {
              textEditingController.clear();
            }
          },
        ),
      ),
    ),
  );
}

6. DropdownButton2 as Popup menu button using customButton parameter:

Example 1 using icon:

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

  @override
  State<CustomButtonTest> createState() => _CustomButtonTestState();
}

class _CustomButtonTestState extends State<CustomButtonTest> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: DropdownButtonHideUnderline(
          child: DropdownButton2(
            customButton: const Icon(
              Icons.list,
              size: 46,
              color: Colors.red,
            ),
            customItemsHeights: [
              ...List<double>.filled(MenuItems.firstItems.length, 48),
              8,
              ...List<double>.filled(MenuItems.secondItems.length, 48),
            ],
            items: [
              ...MenuItems.firstItems.map(
                        (item) =>
                        DropdownMenuItem<MenuItem>(
                          value: item,
                          child: MenuItems.buildItem(item),
                        ),
              ),
              const DropdownMenuItem<Divider>(enabled: false, child: Divider()),
              ...MenuItems.secondItems.map(
                        (item) =>
                        DropdownMenuItem<MenuItem>(
                          value: item,
                          child: MenuItems.buildItem(item),
                        ),
              ),
            ],
            onChanged: (value) {
              MenuItems.onChanged(context, value as MenuItem);
            },
            itemHeight: 48,
            itemPadding: const EdgeInsets.only(left: 16, right: 16),
            dropdownWidth: 160,
            dropdownPadding: const EdgeInsets.symmetric(vertical: 6),
            dropdownDecoration: BoxDecoration(
              borderRadius: BorderRadius.circular(4),
              color: Colors.redAccent,
            ),
            dropdownElevation: 8,
            offset: const Offset(0, 8),
          ),
        ),
      ),
    );
  }
}

class MenuItem {
  final String text;
  final IconData icon;

  const MenuItem({
    required this.text,
    required this.icon,
  });
}

class MenuItems {
  static const List<MenuItem> firstItems = [home, share, settings];
  static const List<MenuItem> secondItems = [logout];

  static const home = MenuItem(text: 'Home', icon: Icons.home);
  static const share = MenuItem(text: 'Share', icon: Icons.share);
  static const settings = MenuItem(text: 'Settings', icon: Icons.settings);
  static const logout = MenuItem(text: 'Log Out', icon: Icons.logout);

  static Widget buildItem(MenuItem item) {
    return Row(
      children: [
        Icon(
                item.icon,
                color: Colors.white,
                size: 22
        ),
        const SizedBox(
          width: 10,
        ),
        Text(
          item.text,
          style: const TextStyle(
            color: Colors.white,
          ),
        ),
      ],
    );
  }

  static onChanged(BuildContext context, MenuItem item) {
    switch (item) {
      case MenuItems.home:
      //Do something
        break;
      case MenuItems.settings:
      //Do something
        break;
      case MenuItems.share:
      //Do something
        break;
      case MenuItems.logout:
      //Do something
        break;
    }
  }
}

Example 2 using image and openWithLongPress parameter:

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

  @override
  State<CustomButtonTest> createState() => _CustomButtonTestState();
}

class _CustomButtonTestState extends State<CustomButtonTest> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: DropdownButtonHideUnderline(
          child: DropdownButton2(
            customButton: Container(
              height: 240,
              width: 240,
              decoration: BoxDecoration(
                borderRadius: BorderRadius.circular(40),
                image: const DecorationImage(
                  image: NetworkImage(
                    'https://cdn.pixabay.com/photo/2020/05/11/06/20/city-5156636_960_720.jpg',
                  ),
                  fit: BoxFit.cover,
                ),
              ),
            ),
            openWithLongPress: true,
            customItemsHeights: [
              ...List<double>.filled(MenuItems.firstItems.length, 48),
              8,
              ...List<double>.filled(MenuItems.secondItems.length, 48),
            ],
            items: [
              ...MenuItems.firstItems.map(
                        (item) => DropdownMenuItem<MenuItem>(
                  value: item,
                  child: MenuItems.buildItem(item),
                ),
              ),
              const DropdownMenuItem<Divider>(enabled: false, child: Divider()),
              ...MenuItems.secondItems.map(
                        (item) => DropdownMenuItem<MenuItem>(
                  value: item,
                  child: MenuItems.buildItem(item),
                ),
              ),
            ],
            onChanged: (value) {
              MenuItems.onChanged(context, value as MenuItem);
            },
            itemHeight: 48,
            itemPadding: const EdgeInsets.only(left: 16, right: 16),
            dropdownWidth: 160,
            dropdownPadding: const EdgeInsets.symmetric(vertical: 6),
            dropdownDecoration: BoxDecoration(
              borderRadius: BorderRadius.circular(4),
              color: Colors.redAccent,
            ),
            dropdownElevation: 8,
            offset: const Offset(40, -4),
          ),
        ),
      ),
    );
  }
}

class MenuItem {
  final String text;
  final IconData icon;

  const MenuItem({
    required this.text,
    required this.icon,
  });
}

class MenuItems {
  static const List<MenuItem> firstItems = [like, share, download];
  static const List<MenuItem> secondItems = [cancel];

  static const like = MenuItem(text: 'Like', icon: Icons.favorite);
  static const share = MenuItem(text: 'Share', icon: Icons.share);
  static const download = MenuItem(text: 'Download', icon: Icons.download);
  static const cancel = MenuItem(text: 'Cancel', icon: Icons.cancel);

  static Widget buildItem(MenuItem item) {
    return Row(
      children: [
        Icon(
          item.icon,
          color: Colors.white,
          size: 22,
        ),
        const SizedBox(
          width: 10,
        ),
        Text(
          item.text,
          style: const TextStyle(
            color: Colors.white,
          ),
        ),
      ],
    );
  }

  static onChanged(BuildContext context, MenuItem item) {
    switch (item) {
      case MenuItems.like:
      //Do something
        break;
      case MenuItems.share:
      //Do something
        break;
      case MenuItems.download:
      //Do something
        break;
      case MenuItems.cancel:
      //Do something
        break;
    }
  }
}

7. Using DropdownButtonFormField2 with Form:

final List<String> genderItems = [
  'Male',
  'Female',
];

String? selectedValue;

final _formKey = GlobalKey<FormState>();

@override
Widget build(BuildContext context) {
  return Scaffold(
    body: Form(
      key: _formKey,
      child: Padding(
        padding: const EdgeInsets.symmetric(horizontal: 80),
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            TextFormField(
              decoration: InputDecoration(
                contentPadding: const EdgeInsets.symmetric(
                  horizontal: 20,
                  vertical: 20,
                ),
                hintText: 'Enter Your Full Name.',
                hintStyle: const TextStyle(fontSize: 14),
                border: OutlineInputBorder(
                  borderRadius: BorderRadius.circular(15),
                ),
              ),
            ),
            const SizedBox(height: 30),
            DropdownButtonFormField2(
              decoration: InputDecoration(
                //Add isDense true and zero Padding.
                //Add Horizontal padding using buttonPadding and Vertical padding by increasing buttonHeight instead of add Padding here so that The whole TextField Button become clickable, and also the dropdown menu open under The whole TextField Button.
                isDense: true,
                contentPadding: EdgeInsets.zero,
                border: OutlineInputBorder(
                  borderRadius: BorderRadius.circular(15),
                ),
                //Add more decoration as you want here
                //Add label If you want but add hint outside the decoration to be aligned in the button perfectly.
              ),
              isExpanded: true,
              hint: const Text(
                'Select Your Gender',
                style: TextStyle(fontSize: 14),
              ),
              icon: const Icon(
                Icons.arrow_drop_down,
                color: Colors.black45,
              ),
              iconSize: 30,
              buttonHeight: 60,
              buttonPadding: const EdgeInsets.only(left: 20, right: 10),
              dropdownDecoration: BoxDecoration(
                borderRadius: BorderRadius.circular(15),
              ),
              items: genderItems
                      .map((item) =>
                      DropdownMenuItem<String>(
                        value: item,
                        child: Text(
                          item,
                          style: const TextStyle(
                            fontSize: 14,
                          ),
                        ),
                      ))
                      .toList(),
              validator: (value) {
                if (value == null) {
                  return 'Please select gender.';
                }
              },
              onChanged: (value) {
                //Do something when changing the item if you want.
              },
              onSaved: (value) {
                selectedValue = value.toString();
              },
            ),
            const SizedBox(height: 30),
            TextButton(
              onPressed: () {
                if (_formKey.currentState!.validate()) {
                  _formKey.currentState!.save();
                }
              },
              child: const Text('Submit Button'),
            ),
          ],
        ),
      ),
    ),
  );
}

CustomDropdownButton2 Widget "customize it to your needs"

class CustomDropdownButton2 extends StatelessWidget {
  final String hint;
  final String? value;
  final List<String> dropdownItems;
  final ValueChanged<String?>? onChanged;
  final DropdownButtonBuilder? selectedItemBuilder;
  final Alignment? hintAlignment;
  final Alignment? valueAlignment;
  final double? buttonHeight, buttonWidth;
  final EdgeInsetsGeometry? buttonPadding;
  final BoxDecoration? buttonDecoration;
  final int? buttonElevation;
  final Widget? icon;
  final double? iconSize;
  final Color? iconEnabledColor;
  final Color? iconDisabledColor;
  final double? itemHeight;
  final EdgeInsetsGeometry? itemPadding;
  final double? dropdownHeight, dropdownWidth;
  final EdgeInsetsGeometry? dropdownPadding;
  final BoxDecoration? dropdownDecoration;
  final int? dropdownElevation;
  final Radius? scrollbarRadius;
  final double? scrollbarThickness;
  final bool? scrollbarAlwaysShow;
  final Offset? offset;

  const CustomDropdownButton2({
    required this.hint,
    required this.value,
    required this.dropdownItems,
    required this.onChanged,
    this.selectedItemBuilder,
    this.hintAlignment,
    this.valueAlignment,
    this.buttonHeight,
    this.buttonWidth,
    this.buttonPadding,
    this.buttonDecoration,
    this.buttonElevation,
    this.icon,
    this.iconSize,
    this.iconEnabledColor,
    this.iconDisabledColor,
    this.itemHeight,
    this.itemPadding,
    this.dropdownHeight,
    this.dropdownWidth,
    this.dropdownPadding,
    this.dropdownDecoration,
    this.dropdownElevation,
    this.scrollbarRadius,
    this.scrollbarThickness,
    this.scrollbarAlwaysShow,
    this.offset,
    Key? key,
  }) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return DropdownButtonHideUnderline(
      child: DropdownButton2(
        //To avoid long text overflowing.
        isExpanded: true,
        hint: Container(
          alignment: hintAlignment,
          child: Text(
            hint,
            overflow: TextOverflow.ellipsis,
            maxLines: 1,
            style: TextStyle(
              fontSize: 14,
              color: Theme.of(context).hintColor,
            ),
          ),
        ),
        value: value,
        items: dropdownItems
                .map((item) => DropdownMenuItem<String>(
          value: item,
          child: Container(
            alignment: valueAlignment,
            child: Text(
              item,
              overflow: TextOverflow.ellipsis,
              maxLines: 1,
              style: const TextStyle(
                fontSize: 14,
              ),
            ),
          ),
        ))
                .toList(),
        onChanged: onChanged,
        selectedItemBuilder: selectedItemBuilder,
        icon: icon ?? const Icon(Icons.arrow_forward_ios_outlined),
        iconSize: iconSize ?? 12,
        iconEnabledColor: iconEnabledColor,
        iconDisabledColor: iconDisabledColor,
        buttonHeight: buttonHeight ?? 40,
        buttonWidth: buttonWidth ?? 140,
        buttonPadding:
        buttonPadding ?? const EdgeInsets.only(left: 14, right: 14),
        buttonDecoration: buttonDecoration ??
                BoxDecoration(
                  borderRadius: BorderRadius.circular(14),
                  border: Border.all(
                    color: Colors.black45,
                  ),
                ),
        buttonElevation: buttonElevation,
        itemHeight: itemHeight ?? 40,
        itemPadding: itemPadding ?? const EdgeInsets.only(left: 14, right: 14),
        //Max height for the dropdown menu & becoming scrollable if there are more items. If you pass Null it will take max height possible for the items.
        dropdownMaxHeight: dropdownHeight ?? 200,
        dropdownWidth: dropdownWidth ?? 140,
        dropdownPadding: dropdownPadding,
        dropdownDecoration: dropdownDecoration ??
                BoxDecoration(
                  borderRadius: BorderRadius.circular(14),
                ),
        dropdownElevation: dropdownElevation ?? 8,
        scrollbarRadius: scrollbarRadius ?? const Radius.circular(40),
        scrollbarThickness: scrollbarThickness,
        scrollbarAlwaysShow: scrollbarAlwaysShow,
        //Null or Offset(0, 0) will open just under the button. You can edit as you want.
        offset: offset,
        dropdownOverButton: false, //Default is false to show menu below button
      ),
    );
  }
}

How simple you can use it:

final List<String> items = [
  'Item1',
  'Item2',
  'Item3',
  'Item4',
  'Item5',
  'Item6',
  'Item7',
  'Item8',
];
String? selectedValue;

@override
Widget build(BuildContext context) {
  return Scaffold(
    body: Center(
      child: CustomDropdownButton2(
        hint: 'Select Item',
        dropdownItems: items,
        value: selectedValue,
        onChanged: (value) {
          setState(() {
            selectedValue = value;
          });
        },
      ),
    ),
  );
}

---

Thanks

If something is missing or you want to add some feature, feel free to open a ticket or contribute!

LICENSE: MIT