How to use API in Dropdown list in Flutter?-CodePudding

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....

CodePudding user response：

Use FutureBuilder to build widgets which requires Future value.

You can return new list of DropDownMenuIems from your getAllCategory() method Instead of updating old Items. Like:

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

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

    if (response.statusCode == 200) {
      List<String> items = [];
      var jsonData = json.decode(response.body) as List;
      for (var element in jsonData) {
        items.add(element["ClassName"]);
      }
      return items;
    } else {
      //Handle Errors
      throw response.statusCode;
    }
  }

Then you can give getAllCategory() as future of FutureBuilder. FutureBuilder will build different widgets according to the provided Future. you can return CircularProgressIndicator until future doesn't have value. After getting your DropDownMenuItems you can return your DropDownMenu. Like:

           FutureBuilder<List<String>>(
              future: getAllCategory(),
              builder: (context, snapshot) {
                if (snapshot.hasData) {
                  var data = snapshot.data!;
                  return DropdownButton(
                    // Initial Value
                    value: dropdownvalue ?? data[0],

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

                    // Array list of items
                    items: data.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!;
                      });
                    },
                  );
                } else {
                  return const CircularProgressIndicator();
                }
              },
            )

Full Code:

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? dropdownvalue;

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

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

    if (response.statusCode == 200) {
      List<String> items = [];
      var jsonData = json.decode(response.body) as List;
      for (var element in jsonData) {
        items.add(element["ClassName"]);
      }
      return items;
    } else {
      throw response.statusCode;
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text("DropDown List"),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            FutureBuilder<List<String>>(
              future: getAllCategory(),
              builder: (context, snapshot) {
                if (snapshot.hasData) {
                  var data = snapshot.data!;
                  return DropdownButton(
                    // Initial Value
                    value: dropdownvalue ?? data[0],

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

                    // Array list of items
                    items: data.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!;
                      });
                    },
                  );
                } else {
                  return const CircularProgressIndicator();
                }
              },
            ),
          ],
        ),
      ),
    );
  }
}

CodePudding user response：

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,
            ),
          ],
        ),
      ),
    );
  }
}