Dropdown in Flutter Example Code.

In Flutter, a dropdown (or dropdown list) is a UI widget that displays a list of options that the user can choose from by tapping on a button. When the user taps on the button, the dropdown expands to show the list of options, and the user can select one of the options. 

<p>How to Create a Dropdown in Flutter

The dropdown widget is typically used in forms, settings screens, or any other scenario where the user needs to choose one option from a list of options. The selected option is usually displayed on the button after the user makes a selection.

What is Dropdown

In Flutter, the DropdownButton widget is used to create a dropdown. It takes in a list of items as well as a default value, and when the user selects an item from the list, the value of the dropdown is updated to the selected item. You can customize the appearance of the dropdown using various properties of the DropdownButton widget, such as icon, iconSize, style, isExpanded, etc.

main.dart

 import 'package:flutter/material.dart';

 void main() {
   runApp(MyApp());
 }

class MyApp extends StatelessWidget {
  final List items = ['Item 1', 'Item 2', 'Item 3', 'Item 4'];
  String dropdownValue = 'Item 1';

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      home: Scaffold(
        appBar: AppBar(
          title: Text('Dropdown List Example'),
        ),
        body: Center(
          child: DropdownButton(
            value: dropdownValue,
            onChanged: (newValue) {
              // setState(() {
              //   dropdownValue = newValue;
              // });
              dropdownValue = newValue!;
              print(dropdownValue);
            },
            items: items.map>((String value) {
              return DropdownMenuItem(
                value: value,
                child: Text(value),
              );
            }).toList(),
          ),
        ),
      ),
    );
  }
} 

In this example, we create a DropdownButton widget that takes in a list of items as well as a default value. 

We then map over the items list to create a list of DropdownMenuItem widgets that we pass into the items parameter of the DropdownButton. 

When the user selects an item from the dropdown list, the onChanged callback is called, which updates the value of dropdownValue. 

You can customize the appearance of the dropdown list using various properties of the DropdownButton widget, such as icon, iconSize, style, isExpanded, etc.