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Simple way to call API in flutter using http package
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Every client side application require connection to server to share the data and get most updated data from server. In the same way flutter also require to call the APIs’ and get data from server and also store the data in server. So in this article i will show you to use Http Request using get and post method.

Http Request are used to communicate between client and server applications. In Flutter we use Http package.

Let’s call APIs in flutter using http package step by step

Step 1 : Create flutter project

First step is to create the fluter application using command line tool or in Android studio.

flutter create example_app

This will create a new project with name example_app then go in to the folder.

Step 2 : Add http package in application

We are going to use http request so we need to add http package first. so add http package in pubspec.yaml

name: example_app
description: A new Flutter project.
publish_to: 'none' # Remove this line if you wish to publish to pub.dev

version: 1.0.0+1

environment:
  sdk: ">=2.15.1 <3.0.0"

dependencies:
  flutter:
    sdk: flutter
  cupertino_icons: ^1.0.2
  http: ^0.13.4

dev_dependencies:
  flutter_test:
    sdk: flutter

  flutter_lints: ^1.0.0

flutter:

  uses-material-design: true

  assets:
    - assets/images/

here we added http: ^0.13.4 in dependencies block

dependencies:
  flutter:
    sdk: flutter
  cupertino_icons: ^1.0.2
  http: ^0.13.4

Also make sure to add latest version always from https://pub.dev/packages/http.

Then run command 

flutter --no-color pub get

Step 3 : Import and use http package in widget

After adding the http package now we can use it in our dart file so import the http package

File : lib/HttpDemo.dart 

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

Here we imported package:http/http.dart and given an alias as http so now lets’s make a http get request and parse the JSON


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

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

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

class _HttpDemoState extends State<HttpDemo> {

   List jsonData=[];

  @override
  void initState() {
    super.initState();
    getJsonData();


  }
   getJsonData() async{

    final response = await http
        .get(Uri.parse('https://jsonplaceholder.typicode.com/albums'));
   
    if (response.statusCode == 200) {
      // If the server did return a 200 OK response,
      // then parse the JSON.

      setState(() {
        jsonData =  json.decode(response.body);
        
      });
    } else {
      // If the server did not return a 200 OK response,
      // then throw an exception.
      throw Exception('Failed to load album');
    }
  }

  buildLayout(){
    if(jsonData.isEmpty) {
    return  Center(
        child: SizedBox(
          child: CircularProgressIndicator(
            backgroundColor: Theme
                .of(context)
                .primaryColor,
            strokeWidth: 2,
          ),
          height: 25.0,
          width: 25.0,
        ),
      );
    }
    else{

      return ListView(
        children: jsonData.map((e){ 
          return Container(
          margin: const EdgeInsets.all(5),
          child: "Title : "+Text(e['title']  )
          );
        }
    ).toList(),
      );
    }
  }


  @override
  Widget build(BuildContext context) {
    return  MaterialApp(
        title: 'Flutter Demo',
        theme: ThemeData(
          primarySwatch: Colors.blue,
        ),
        home: Scaffold(
        appBar: AppBar(
        title: const Text('Readerstacks Http Demo'),
    ),

    body:buildLayout()
    )
    );
  }
}

Here we used getJsonData to fetch http request and then on response setState again to rebuild the widget.

 getJsonData() async{

    final response = await http
        .get(Uri.parse('https://jsonplaceholder.typicode.com/albums'));
    
    if (response.statusCode == 200) {
      // If the server did return a 200 OK response,
      // then parse the JSON.

      setState(() {
        jsonData =  json.decode(response.body);
        
      });
    } else {
      // If the server did not return a 200 OK response,
      // then throw an exception.
      throw Exception('Failed to load album');
    }
  }

Here we used json.decode to decode the response in List using package import ‘dart:convert’.

we also create a method buildLayout to show loading indicator until jsonData variable is empty once its filled with data then we are showing list view as below

 buildLayout(){
    if(jsonData.isEmpty) {
    return  Center(
        child: SizedBox(
          child: CircularProgressIndicator(
            backgroundColor: Theme
                .of(context)
                .primaryColor,
            strokeWidth: 2,
          ),
          height: 25.0,
          width: 25.0,
        ),
      );
    }
    else{

      return ListView(
        children: jsonData.map((e){ 
          return Container(
          margin: const EdgeInsets.all(5),
          child: "Title : "+Text(e['title']  )
          );
        }
    ).toList(),
      );
    }
  }

Step 3 : Add Page to main file

Add you new pages to main.dart and start tabbing.

import 'package:flutter/material.dart';
import 'package:example_app/HttpDemo.dart';

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

Step 4: Run the project

Simply run the project using command line or in android studio to check the implementation.

flutter run lib/main.dart

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