How to use API in Dropdown list in Flutter?

Question

Output in Working Condtion Hello Flutter/Dart Programmers, I'm new in Flutter. below code about Dropdown is working without API, but i wants API data to display in Dropdown list.... i need help

import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
import 'dart:convert';
import 'dart:async';

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

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter DropDownButton',
      theme: ThemeData(
        primarySwatch: Colors.green,
      ),
      home: const MyHomePage(),
      debugShowCheckedModeBanner: false,
    );
  }
}

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

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  String selectValue = "";
  List categoryItemlist = [];

  //List categoryItemlist = List();  //it is not working

  // ***********************************************************
  // Fetch data from JSON/API File
  Future getAllCategory() async {
    var baseUrl = "https://gssskhokhar.com/api/classes/";

    http.Response response = await http.get(Uri.parse(baseUrl));

    if (response.statusCode == 200) {
      var jsonData = json.decode(response.body);
      setState(() {
        categoryItemlist = jsonData;
      });
    }
    print(categoryItemlist);
  }

  @override
  void initState() {
    super.initState();
    getAllCategory();
  }
  // ***********************************************************

// Initial Selected Value
  String dropdownvalue = 'Item 1';

// List of items in our dropdown menu
  var items = [
    'Item 1',
    'Item 2',
    'Item 3',
    'Item 4',
    'Item 5',
  ];
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text("DropDown List"),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            DropdownButton(
              // Initial Value
              value: dropdownvalue,

              // Down Arrow Icon
              icon: const Icon(Icons.keyboard_arrow_down),

              // Array list of items
              items: items.map((String items) {
                return DropdownMenuItem(
                  value: items,
                  child: Text(items),
                );
              }).toList(),
              // After selecting the desired option,it will
              // change button value to selected value
              onChanged: (String? newValue) {
                setState(() {
                  dropdownvalue = newValue!;
                });
              },
            ),
          ],
        ),
      ),
    );
  }
}

Output Pic is attach with working condition but without API/JSON. but i wants API data to display in Dropdown list....

Answer 1

i think you need this codes

import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
import 'dart:convert';
import 'dart:async';

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

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter DropDownButton',
      theme: ThemeData(
        primarySwatch: Colors.green,
      ),
      home: const MyHomePage(),
      debugShowCheckedModeBanner: false,
    );
  }
}

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

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  List categoryItemlist = [];

  Future getAllCategory() async {
    var baseUrl = "https://gssskhokhar.com/api/classes/";

    http.Response response = await http.get(Uri.parse(baseUrl));

    if (response.statusCode == 200) {
      var jsonData = json.decode(response.body);
      setState(() {
        categoryItemlist = jsonData;
      });
    }
  }

  @override
  void initState() {
    super.initState();
    getAllCategory();
  }

  var dropdownvalue;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text("DropDown List"),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            DropdownButton(
              hint: Text('hooseNumber'),
              items: categoryItemlist.map((item) {
                return DropdownMenuItem(
                  value: item['ClassCode'].toString(),
                  child: Text(item['ClassName'].toString()),
                );
              }).toList(),
              onChanged: (newVal) {
                setState(() {
                  dropdownvalue = newVal;
                });
              },
              value: dropdownvalue,
            ),
          ],
        ),
      ),
    );
  }
}