Introduction

Hello and welcome to my new blog on Rest API in Flutter. In this blog, we shall discuss fetching data, deleting data, updating data using a JSON file. Nowadays the use of API in an app is very common, almost every app we use in daily life use API to display the uses data. We will use http package, which provides advanced methods to perform various operations. REST API uses a simple http calls to communicate with JSON data. Each request returns a Future<Response>.

Table of content

Need of http package & methods

Setting up the project

Creating a simple get Request

Handling the error code

Decoding the JSON data

Creating UI classes

Displaying the response on the screen

Updating the data

Deleting the data

Sending the data

Need of http Package?

• :: It uses await and async feature.
• :: It provides various method.
• :: It provides class and http to perform web request.

:: Core Methods in http package?

Listing Http package methods woth giving a try and of much usage

1. post Method

:: This method uses a URL and POST method to post the data and return a Future<Response>. It is used to send the data on the web.

2. get Method

:: get method uses a URL and fetches the data in JSON format.

3. delete Method

:: This method is used to delete the data using the DELETE method.

4. head Method

:: Uses the URL to request the data using the HEAD method and return the response as Future<Response>.

5. read Method

:: It is similar as get method, used to read the data.

6. put Method

:: It uses the specified URL and update the data specified by the user using the PUT method.

7. patch Method

It is very similar to the put method, used to update the data.

:: Setting up the Project

Install the http dependency

Add the following dependency in pubspec.yaml file

dependencies:
  http:

Import the package as http

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

Also Import import 'dart:convert'; to convert the JSON data.

: Creating a Request

Future<List<Fruit>> fetchFruit() async {
  final response = await http.get(url);
}
String url = "Your_URL";

This is the basic request using get method to fetch the data from the specified URL in the JSON format.

: Handling the error code

final response = await http.get(
      'url');
  if (response.statusCode == 200) {
    //displaY UI
    } else {
    //SHOW ERROR MESSAGE
    }
}

If the response status code is 200 then we can display the requested data otherwise we can show the error message to the users.

: Decoding the JSON data

List<Fruit> decodeFruit(String responseBody) {
  final parsed = json.decode(responseBody).cast<Map<String, dynamic>>();
  return parsed.map<Fruit>((json) => Fruit.fromMap(json)).toList();
}

: Creating a Fruit class

class Fruit {
  final int id;
  final String title;
  final String imageUrl;
  final int quantity;

  Fruit(
    this.id,
    this.title,
    this.imageUrl,
    this.quantity,
  );
  factory Fruit.fromMap(Map<String, dynamic> json) {
    return Fruit(json['id'], json['title'], json['imageUrl'], json['quantity']);
  }
  factory Fruit.fromJson(Map<String, dynamic> json) {
    return Fruit(json['id'], json['title'], json['imageUrl'], json['quantity']);
  }
}

:: Creating a FruitList class

import 'package:flutter/material.dart';
import 'fruit.dart';
import 'fruitItem.dart';

class FruitList extends StatelessWidget {
  final List<Fruit> items;

  FruitList({Key key, this.items});

  @override
  Widget build(BuildContext context) {
    return ListView.builder(
      itemCount: items.length,
      itemBuilder: (context, index) {
        return FruitItem(item: items[index]);
      },
    );
  }
}

: Creating the FruitItem

import 'package:flutter/material.dart';

import 'fruit.dart';

class FruitItem extends StatelessWidget {
  FruitItem({this.item});

  final Fruit item;

  Widget build(BuildContext context) {
    return Container(
        padding: EdgeInsets.all(2),
        height: 140,
        child: Card(
          elevation: 5,
          child: Row(
              mainAxisAlignment: MainAxisAlignment.spaceEvenly,
              children: <Widget>[
                Image.network(
                  this.item.imageUrl,
                  width: 200,
                ),
                Expanded(
                    child: Container(
                        padding: EdgeInsets.all(5),
                        child: Column(
                          mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                          children: <Widget>[
                            Text(this.item.title,
                                style: TextStyle(fontWeight: FontWeight.bold)),
                            Text("id:${this.item.id}"),
                            Text("quantity:${this.item.quantity}"),
                          ],
                        )))
              ]),
        ));
  }
}

: Displaying the response on the screen

class MyHomePage extends StatelessWidget {
  final String title;
  final Future<List<Fruit>> products;

  MyHomePage({Key key, this.title, this.products}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(title: Text("Product Navigation"),
         ),
        body: Center(
          child: FutureBuilder<List<Fruit>>(
            future: products,
            builder: (context, snapshot) {
              if (snapshot.hasError) print(snapshot.error);
              return snapshot.hasData
                  ? FruitList(items: snapshot.data)
                  : Center(child: CircularProgressIndicator());
            },
          ),
        ));
  }
}

: Updating the data

Future<Fruit> updateFruit(String title) async {
  final http.Response response = await http.put(
    'url/$id',
    headers: <String, String>{
      'Content-Type': 'application/json; charset=UTF-8',
    },
    body: jsonEncode(<String, String>{
      'title': title,
    }),
  );

  if (response.statusCode == 200) {
    return Fruit.fromJson(json.decode(response.body));
  } else {
    throw Exception('Failed to update album.');
  }
}

: Deleting the data

Future<Fruit> deleteAlbum(int id) async {
  final http.Response response = await http.delete(
    'url/$id',
    headers: <String, String>{
      'Content-Type': 'application/json; charset=UTF-8',
    },
  );

  if (response.statusCode == 200) {
    return Fruit.fromJson(json.decode(response.body));
  } else {
    throw Exception('Failed to delete album.');
  }
}

: Sending the data

Future<Fruit> sendFruit(
    String title, int id, String imageUrl, int quantity) async {
  final http.Response response = await http.post(
    'url',
    headers: <String, String>{
      'Content-Type': 'application/json; charset=UTF-8',
    },
    body: jsonEncode(<String, String>{
      'title': title,
      'id': id.toString(),
      'imageUrl': imageUrl,
      'quantity': quantity.toString()
    }),
  );
  if (response.statusCode == 201) {
    return Fruit.fromJson(json.decode(response.body));
  } else {
    throw Exception('Failed to load album');
  }
}

Github Link

flutter-devs/rest_API_demo
A new Flutter application. This project is a starting point for a Flutter application. A few resources to get you…github.com

🌸🌼🌸 Thank you for reading. 🌸🌼🌸🌼

From Our Parent Company Aeologic

Aeologic Technologies is a leading AI-driven digital transformation company in India, helping businesses unlock growth with AI automation, IoT solutions, and custom web & mobile app development. We also specialize in AIDC solutions and technical manpower augmentation, offering end-to-end support from strategy and design to deployment and optimization.

Trusted across industries like manufacturing, healthcare, logistics, BFSI, and smart cities, Aeologic combines innovation with deep industry expertise to deliver future-ready solutions.

Feel free to connect with us:
And read more articles from FlutterDevs.com

FlutterDevs team of Flutter developers to build high-quality and functionally-rich apps. Hire flutter developer for your cross-platform Flutter mobile app project on an hourly or full-time basis as per your requirement! You can connect with us on Facebook, GitHub, Twitter, and LinkedIn for any flutter related queries.

We welcome feedback and hope that you share what you’re working on using #FlutterDevs. We truly enjoy seeing how you use Flutter to build beautiful, interactive web experiences!.

Related: Rest API Using GetX

Related: Integrating REST APIs into Your FlutterFlow App

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Introduction

In this blog, we shall discuss how to generate and scan QR code in your Flutter app. QR code is widely used by the payment gateway and in many other services because they can store text, URL, email address, ph. numbers or any other form of data. Nowadays QR code scanning can be done very easily through mobile phones, they do not require special devices for scanning.

Key Features of Bar code and QR code

1. Safe and secure, they are only readable by machines.
2. They can store any form of data easily
3. Quick Response
4. Data stored in static QR codes can not be edited.
5. Easy to generate and scan

Table of content

1. Installing Package
2. Generate QR code
3. Scan QR code
4. GitHub Link

:: Installing Package

Update your pubspec.yaml file with the following package:

barcode_scan | Flutter Package
example/lib/main.dart import ‘dart:async’; import ‘dart:io’ show Platform; import…pub.dev

qr_flutter | Flutter Package
QR. Flutter is a Flutter library for simple and fast QR code rendering via a Widget or custom painter.pub.dev

dependencies:
  barcode_scan:
  qr_flutter:

:: Generate QR code

Import import ‘package:qr_flutter/qr_flutter.dart’;

Let’s build a text field to take input from the user:

Initialize a textEditingController for the field:

TextEditingController qrTextController = TextEditingController();

Create a text field with hint text:

TextField(
  controller: qrTextController,
  decoration: InputDecoration(
    hintText: "please enter some data",
  ),
),

Code to design the text field:

Padding(
  padding: const EdgeInsets.all(8.0),
  child: Card(
    elevation: 5,
    child: ListTile(
      leading: Icon(Icons.edit),
      trailing: FlatButton(
        child: Text(
          "ENTER",
          style: TextStyle(
            color: Colors.white,
          ),
        ),
        color: Colors.green,
        onPressed: () {
        },
      ),
      title: TextField(
        controller: qrTextController,
        decoration: InputDecoration(
          hintText: "please enter some data",
        ),
      ),
    ),
  ),
),

Submitting the text entered by the user to the QR code data:

onPressed: () {
  setState(() {
    dummyData = qrTextController.text == ""
        ? null
        : qrTextController.text;
  });
},

dummyData is a string that is the data for QR code. Here I have declared a condition to specify the dummyData , if the qrTextController is “” then it will be null otherwise qrTextController will be the data of the dummyData string.

Creating a QrImage

import 'package:qr_flutter/qr_flutter.dart'; package provides us QrImage() class to create a code image of the data given by the user.

QrImage(
    data: dummyData,
  ),

Creating a QrImage with embeddedImage

QrImage(
    embeddedImage: NetworkImage(
      "https://avatars1.githubusercontent.com/u/41328571?s=280&v=4",
    ),
    data: dummyData,
  ),

generate.dart

import 'package:flutter/material.dart';
import 'package:qr_flutter/qr_flutter.dart';

class GeneratePage extends StatefulWidget {
  @override
  State<StatefulWidget> createState() => GeneratePageState();
}

class GeneratePageState extends State<GeneratePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Generate QR code'),
      ),
      body: ListView(
        children: <Widget>[
          Padding(
            padding: const EdgeInsets.all(8.0),
            child: Card(
              elevation: 5,
              child: ListTile(
                leading: Icon(Icons.edit),
                trailing: FlatButton(
                  child: Text(
                    "ENTER",
                    style: TextStyle(
                      color: Colors.white,
                    ),
                  ),
                  color: Colors.green,
                  onPressed: () {
                    setState(() {
                      dummyData = qrTextController.text == ""
                          ? null
                          : qrTextController.text;
                    });
                  },
                ),
                title: TextField(
                  controller: qrTextController,
                  decoration: InputDecoration(
                    hintText: "please enter some data",
                  ),
                ),
              ),
            ),
          ),
          (dummyData == null)
              ? Center(child: Text("enter some text to display qr code..."))
              : QrImage(
                  embeddedImage: NetworkImage(
                    "https://avatars1.githubusercontent.com/u/41328571?s=280&v=4",
                  ),
                  data: dummyData,
                  gapless: true,
                ),
        ],
      ),
    );
  }
}

String dummyData;

TextEditingController qrTextController = TextEditingController();

:: Scan Qr Code

Import import ‘package:barcode_scan/barcode_scan.dart’; and initialize the

String qrCodeResult; variable to store the result of the Qr code.

Creating a scan function

Future<void> _scan() async {
  ScanResult codeSanner = await BarcodeScanner.scan();
}

BrcodeScanner class provides us scan() method to scan the Qr code. BarcodeScanner.scan() returns a ScanResult that contains the text return by the Qr Code scanner.

Setting up the result of the scanner to the qrCodeResult

Future<void> _scan() async {
  ScanResult codeSanner = await BarcodeScanner.scan(),
  );
  setState(() {
    qrCodeResult = codeSanner.rawContent;
  });
}

Setting up the camera option

scan() method contains option a property that can be used to change the camera (eg. front Camera or Back Camera).

Future<void> _scan() async {
  ScanResult codeSanner = await BarcodeScanner.scan(
    options: ScanOptions(
      useCamera: camera,
    ),
  ); 
}
int camera = 1;

ScanOptions provides us useCamera property to change the camera type.

1. useCamera takes an integer 1 or -1.
2. If useCamera value is 1 then the front Camera works to scan the Qr code.
3. If useCamera value is -1 then back camera works to scan the Qr code.

To switch the camera I have built the following logic:

appBar: AppBar(
  title: Text("Scan using:" + (backCamera ? "Front Cam" : "Back Cam")),
  actions: <Widget>[
    IconButton(
      icon: backCamera
          ? Icon(Ionicons.ios_reverse_camera)
          : Icon(Icons.camera),
      onPressed: () {
        setState(() {
          backCamera = !backCamera;
          camera = backCamera ? 1 : -1;
        });
      },
    )
  ],
),

Initializing the scan() function

IconButton(
  icon: Icon(MaterialCommunityIcons.qrcode_scan),
  onPressed: () {
    _scan();
  },
)

Displaying the result

Center(
  child: Text(
    (qrCodeResult == null) || (qrCodeResult == "")
        ? "Please Scan to show some result"
        : "Result:" + qrCodeResult,
    style: TextStyle(fontSize: 20.0, fontWeight: FontWeight.w900),
  ),
)

scan.dart

import 'package:barcode_scan/barcode_scan.dart';
import 'package:flutter/material.dart';
import 'package:flutter_vector_icons/flutter_vector_icons.dart';

class ScanPage extends StatefulWidget {
  @override
  _ScanPageState createState() => _ScanPageState();
}

class _ScanPageState extends State<ScanPage> {
  String qrCodeResult;
  bool backCamera = true;

 @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: Text("Scan using:" + (backCamera ? "Front Cam" : "Back Cam")),
          actions: <Widget>[
            IconButton(
              icon: backCamera
                  ? Icon(Ionicons.ios_reverse_camera)
                  : Icon(Icons.camera),
              onPressed: () {
                setState(() {
                  backCamera = !backCamera;
                  camera = backCamera ? 1 : -1;
                });
              },
            ),
            IconButton(
              icon: Icon(MaterialCommunityIcons.qrcode_scan),
              onPressed: () {
                _scan();
              },
            )
          ],
        ),
        body: Center(
          child: Text(
            (qrCodeResult == null) || (qrCodeResult == "")
                ? "Please Scan to show some result"
                : "Result:" + qrCodeResult,
            style: TextStyle(fontSize: 20.0, fontWeight: FontWeight.w900),
          ),
        ));
  }

 Future<void> _scan() async {
    ScanResult codeSanner = await BarcodeScanner.scan(
      options: ScanOptions(
        useCamera: camera,
      ),
    );
    setState(() {
      qrCodeResult = codeSanner.rawContent;
    });
  }
}

int camera = 1;

Our app will look like this

:: GitHub Link

flutter-devs/qr_code_demo
A new Flutter application. This project is a starting point for a Flutter application. A few resources to get you…github.com

🌸🌼🌸 Thank you for reading. 🌸🌼🌸🌼

From Our Parent Company Aeologic

Aeologic Technologies is a leading AI-driven digital transformation company in India, helping businesses unlock growth with AI automation, IoT solutions, and custom web & mobile app development. We also specialize in AIDC solutions and technical manpower augmentation, offering end-to-end support from strategy and design to deployment and optimization.

Trusted across industries like manufacturing, healthcare, logistics, BFSI, and smart cities, Aeologic combines innovation with deep industry expertise to deliver future-ready solutions.

Feel free to connect with us:
And read more articles from FlutterDevs.com

FlutterDevs team of Flutter developers to build high-quality and functionally-rich apps. Hire flutter developer for your cross-platform Flutter mobile app project on an hourly or full-time basis as per your requirement! You can connect with us on Facebook, GitHub, Twitter, and LinkedIn for any flutter related queries.

We welcome feedback and hope that you share what you’re working on using #FlutterDevs. We truly enjoy seeing how you use Flutter to build beautiful, interactive web experiences!.

Related: Improve code style using lint rules in Flutter

Related: Pin Code Fields In Flutter

Need expert help building your Flutter app? Talk to FlutterExperts for architecture, development, and consulting support.