Learn to Generate QR Codes in Flutter

Table of Contents

1. Introduction
2. QR Codes in Flutter
3. Setting up the QR Code Package
4. Creating the Basic UI Components
5. Generating the QR Code
6. Styling the QR Code
7. Customizing QR Code Shape
8. Changing QR Code Color
9. Adding an Embedded Image
10. Generating Encrypted QR Codes
11. Conclusion

QR Codes in Flutter: A Comprehensive Guide

QR codes have become increasingly popular in today's digital age. Whether it's for marketing purposes or personal use, Flutter app developers can leverage the power of QR codes to enhance their applications. In this article, we will explore how to integrate QR code functionality into a Flutter app using a package called "QR_flutter". By following these step-by-step instructions, you will be able to generate QR codes for any string data within your app.

1. Introduction

QR codes, short for Quick Response codes, are two-dimensional barcodes that can store large amounts of data. They are widely used for various purposes, such as sharing URLs, contact information, or even unlocking features in an app. Integrating QR code functionality into your Flutter app can greatly enhance user experience and provide a seamless way to share and access information.

2. QR Codes in Flutter

To implement QR code functionality in a Flutter app, we will be using the "QR_flutter" package. This package provides a comprehensive set of widgets and methods to generate QR codes based on input data. Before we dive into the coding part, we need to make sure we have the latest version of the "QR_flutter" package installed.

3. Setting up the QR Code Package

To get started, we need to add the "QR_flutter" package to our Flutter project. Open the "pubspec.yaml" file and add the following line under the "dependencies" section:

dependencies:
  qr_flutter: ^4.0.0

Make sure to check for the latest version of the package and update the version number accordingly. Save the file and run the command flutter pub get in your terminal to fetch the package.

4. Creating the Basic UI Components

Before we can generate QR codes, we need to build the basic UI components of our app. This includes an input field where users can enter the data for which they want to generate a QR code. We will also add a button to trigger the QR code generation process.

In the main.dart file, start by importing the necessary packages:

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

Next, build the app's UI components inside the build() method of the HomePage class. We will create a TextField widget for the input field and a RaisedButton for the QR code generation button.

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  final TextEditingController _textEditingController =
      TextEditingController();
  String _data = '';

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: buildAppBar(),
      body: Column(
        children: [
          TextField(
            controller: _textEditingController,
            decoration: InputDecoration(
              hintText: 'Enter data',
            ),
          ),
          RaisedButton(
            onPressed: generateQRCode,
            child: Text('Generate QR Code'),
          ),
          SizedBox(height: 20),
          buildQRCode(),
        ],
      ),
    );
  }

5. Generating the QR Code

Now that we have set up the basic UI components, let's move on to generating the QR code. Inside the _HomePageState class, create a method called generateQRCode().

void generateQRCode() {
  String input = _textEditingController.text;

  if (input.isEmpty) {
    ScaffoldMessenger.of(context).showSnackBar(
      SnackBar(
        content: Text('Please enter a valid input.'),
      ),
    );
  } else {
    setState(() {
      _data = input;
    });
  }
}

This method extracts the input data from the TextField widget and validates it. If the input is empty, a SnackBar is displayed to prompt the user to enter a valid value. Otherwise, the input data is stored in the _data variable using the setState method, triggering a UI update.

6. Styling the QR Code

By default, the QR code generated by the "QR_flutter" package is square in shape with black modules. However, you can customize the styling of the QR code to match your app's design.

To do this, we will pass additional parameters to the QrImage widget. For example, you can specify the color, padding, and even add an embedded image to the center of the QR code.

buildQRCode() {
  if (_data.isEmpty) {
    return SizedBox.shrink();
  } else {
    return QrImage(
      data: _data,
      version: QrVersions.auto,
      size: 200.0,
      backgroundColor: Colors.white,
      color: Colors.black,
      errorCorrectionLevel: QrErrorCorrectLevel.H,
      errorStateBuilder: (cxt, err) {
        return Icon(Icons.error_outline);
      },
    );
  }
}

In this example, the QrImage widget is only rendered if the _data variable is not empty. We set the data parameter to the value stored in _data. We also specify the backgroundColor, color, and size of the QR code. Additionally, we handle potential errors by rendering an error icon when necessary.

7. Customizing QR Code Shape

Apart from changing the color and size of the QR code, you can also customize its shape. By default, the QR code is square, but you can make it circular by wrapping the QrImage widget with a ClipOval widget.

buildQRCode() {
  if (_data.isEmpty) {
    return SizedBox.shrink();
  } else {
    return ClipOval(
      child: QrImage(
        // QR code parameters...
      ),
    );
  }
}

By using the ClipOval widget, the corners of the QR code will be clipped, resulting in a circular shape. This can be a great way to add a unique touch to your QR codes.

8. Changing QR Code Color

In addition to customizing the shape, you can also change the color of the QR code. With the "QR_flutter" package, you can easily modify the color of both the modules and the eye of the QR code.

buildQRCode() {
  if (_data.isEmpty) {
    return SizedBox.shrink();
  } else {
    return QrImage(
      data: _data,
      version: QrVersions.auto,
      size: 200.0,
      backgroundColor: Colors.white,
      color: Colors.green, // Change the color here
      eyeStyle: QrEyeStyle(
        eyeShape: QrEyeShape.square,
        color: Colors.red, // Change the eye color here
      ),
    );
  }
}

By modifying the color parameter, you can give your QR code a unique look that suits your app's branding. Similarly, you can adjust the color of the eye by using the eyeStyle parameter.

9. Adding an Embedded Image

If you want to further personalize your QR code, you can add an embedded image at the center. This is useful when you want to display a logo or any other image within the QR code.

To add an embedded image, create a new DecorationImage and pass it as the embeddedImage parameter to the QrImage widget.

buildQRCode() {
  if (_data.isEmpty) {
    return SizedBox.shrink();
  } else {
    return QrImage(
      data: _data,
      version: QrVersions.auto,
      size: 200.0,
      backgroundColor: Colors.white,
      color: Colors.black,
      embeddedImage: AssetImage('assets/logo.png'),
      embeddedImageStyle: QrEmbeddedImageStyle(
        size: Size(40, 40),
      ),
    );
  }
}

Make sure you have the image file in your project's assets folder and add it to the pubspec.yaml file.

10. Generating Encrypted QR Codes

In some cases, you may want to encrypt the data before generating a QR code. This adds an extra layer of security, ensuring that only authorized users can access the information contained in the QR code.

To encrypt the data, you can use popular encryption algorithms like AES or RSA. Once the data is encrypted, you can pass it to the QrImage widget as usual.

11. Conclusion

In this tutorial, we have explored how to integrate QR code functionality into a Flutter app using the "QR_flutter" package. We have covered various aspects, from setting up the package to customizing the QR code's shape, color, and content. By following these step-by-step instructions, you can enhance your Flutter app user experience by allowing users to generate QR codes for any string data.

QR codes provide a convenient way to share and access information, and with Flutter's versatility, you can seamlessly integrate this functionality into your app. So go ahead and start implementing QR codes in your Flutter app today!