How to use Array key value pair in Flutter DropDownButton

In this Google flutter code example we are going to learn how to use Array key value pair in Flutter DropDownButton.

The code is based on flutter version 1.0.0

Main.dart (App entry point)

import 'package:flutter/material.dart';
import 'week2/dropdownbutton_key_value_pair.dart';

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

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        // This is the theme of your application.
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primarySwatch below to and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or simply save your changes to "hot reload" in a Flutter IDE).
        // Notice that the counter didn't reset back to zero; the application
        // is not restarted.
      //home: MyHomePage(title: 'Flutter Demo Home Page'),
      home: KeyValuePairDropdown(),


import 'package:flutter/material.dart';

class KeyValuePairDropdown extends StatefulWidget {
  //Add key-value pair data here
  KeyValuePairDropdownState createState() {
    return new KeyValuePairDropdownState();

class KeyValuePairDropdownState extends State<KeyValuePairDropdown> {
  List<KeyValueModel> _datas = [
    KeyValueModel(key: "Key 1", value: "Value 1"),
    KeyValueModel(key: "Key 2", value: "Value 2"),
    KeyValueModel(key: "Key 3", value: "Value 3"),
    KeyValueModel(key: "Key 4", value: "Value 4"),
    KeyValueModel(key: "Key 5", value: "Value 5"),

  String _selectedValue = "";

  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Key value Pair - DropdownButton'),
      body: Center(
        child: Column(
          mainAxisSize: MainAxisSize.max,
          children: <Widget>[
              items: _datas
                  .map((data) => DropdownMenuItem<String>(
                        child: Text(data.key),
                        value: data.value,
              onChanged: (String value) {
                setState(() => _selectedValue = value);
              hint: Text('Select Key'),
              height: 25.0,

//Create a Model class to hold key-value pair data
class KeyValueModel {
  String key;
  String value;

  KeyValueModel({this.key, this.value});

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