Creating Dropdown in Flutter using Generics

creating dropdown in flutter with generics#

I will show you how to create a dropdown with list of values in flutter.

There is already a widget for that which is DropdownButton() it also have item property which is list of widget in that item we will add list of DropdownMenuItem like below.

i will give you a practical example of using dropdown, first i will create a custom widget which will return DropdownButton so that we can use same widget at a multiple location.

You need to create a model class for showing data into dropdown. i will use generic dropdown so that it will work with anykind of model class.

lets first create a model class of users.

class Users {
  final int id;
  final String username;
  final String fullName;

    required this.username,
    required this.fullName,

  String toString() {
    // TODO: implement toString
    return this.fullName;

make sure toString() method is defined because we are using that methods return type to show text in DropdownItem.

Now create a statefull widget in widgets folder with name CustomDropdown.

i will give you all code below for custom dropdown.


import 'package:flutter/material.dart';

class CustomDropdown<T> extends StatefulWidget {
  const CustomDropdown(
      {Key? key,
      required this.modelList,
      required this.model,
      required this.callback})
      : super(key: key);
  final List<T?> modelList;
  final T? model;
  final Function(T?) callback;

  State<CustomDropdown<T>> createState() => _CustomDropdownState<T>();

class _CustomDropdownState<T> extends State<CustomDropdown<T>> {
  T? labour;

  void initState() {
    labour = widget.model;

  Widget build(BuildContext context) {
    return Container(
      child: DropdownButton<T>(
        underline: const SizedBox(),
        elevation: 0,
        isDense: true,
        hint: const Text("Select "),
        value: labour,
        items: value) {
          return DropdownMenuItem<T>(
            value: value,
            child: Text(value.toString()),
        onChanged: (val) {
          setState(() {
            labour = val;

I have used generics to make it compatible with anykind of model class.

I can use it with any model class like below

List<Users?> usersArr = [
Users(id: 1, username: "abc", fullName: "ABC"),
Users(id: 2, username: "xyz", fullName: "XYZ"),
                modelList: usersArr,
                model: usersArr[0],
                callback: (user) {

with the help of generics you can create many custom widgets which will be very helpfull for others as well.

if you have any doubt please comment.

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