Learn How to Build a QR & Barcode Scanner App in Android Studio

Learn How to Build a QR & Barcode Scanner App in Android Studio

Table of Contents:

1. Introduction
2. Setting up the QR Code Scanner 2.1 Adding Dependency 2.2 Adding Runtime Permission
3. Designing the Layout
4. Implementing the Code Scanner Function
5. Handling Camera Runtime Permission
6. Testing the Code Scanner
7. Conclusion

Introduction

In this tutorial, we will learn how to Create a QR code scanner in Android using Kotlin. A QR code scanner is a useful tool for decoding QR codes and barcodes. We will be using a library called Code Scanner by Yuri Budiev to implement the functionality. The scanner will ask for camera permission and will be able to scan both QR codes and barcodes. Additionally, we will add features like autofocus, flashlight control, and a user-friendly interface. So let's get started with setting up the QR code scanner.

Setting up the QR Code Scanner

To set up the QR code scanner, we need to add the necessary dependencies and configure the runtime permission.

2.1 Adding Dependency

The first step is to add the required dependency to our project. We will be using the Code Scanner library by Yuri Budiev. You can find the library on GitHub and check the supported formats before proceeding. Copy the implementation code from the library's documentation and paste it into the project's build.gradle file under the "dependencies" section. Once you have pasted the code, click on "Sync Now" to sync the project.

2.2 Adding Runtime Permission

Next, we need to add the necessary runtime permission for accessing the camera. Open the manifest file and add the following line of code within the "manifest" tag:

<uses-permission android:name="android.permission.CAMERA" />

This line specifies that the app requires camera permission.

Designing the Layout

Now, let's move on to designing the layout for our QR code scanner. Open the activity_main.xml layout file and make the following changes:

• Change the root layout from ConstraintLayout to RelativeLayout.
• Remove any existing views and add the CodeScanner view to the layout.
• Set the width to "match_parent" and Height to "400dp" to cover half the screen.
• Assign an id to the CodeScanner view (e.g., scanner_view).
• Add attributes for autofocus and flash buttons to make them visible and set their colors.
• Optionally, add a mask color to create a transparent background for the scanner.

Implementing the Code Scanner Function

Now, let's implement the code scanner function. In the MainActivity.kt file, create a private constant named "cameraRequestCode" with a value of 101. Then, create a private late-initialized variable named "codeScanner" of Type "CodeScanner".

Next, create a function named "startCodeScanner" that will initialize and configure the code scanner. Inside the function, initialize the "codeScanner" variable by assigning it a new instance of CodeScanner with the Current Context. Set the camera to the back camera using "codeScanner.camera = CodeScanner.CAMERA_BACK". Specify the desired barcode formats using "codeScanner.formats = CodeScanner.ALL_FORMATS". Set the autofocus mode to "CodeScanner.AutoFocusMode.SAFE" for better scanning accuracy. Enable continuous scan mode with "codeScanner.scanMode = CodeScanner.ScanMode.CONTINUOUS". Optionally, enable or disable autofocus and flash Based on your requirements.

Next, add the decoder callback and error callback functions to handle successful decoding of codes and error scenarios, respectively.

Finally, override the onResume and onPause methods to start and release the code scanner's resources, respectively.

Handling Camera Runtime Permission

To handle the camera runtime permission, create a private function named "setupPermissions" that will check if the camera permission is granted or not. Use the "ContextCompat.checkSelfPermission" function to check the permission status. If the permission is not granted, call another function named "makeRequest" to request the permission from the user. In the "makeRequest" function, use "ActivityCompat.requestPermissions" to request the camera permission. Override the "onRequestPermissionsResult" method to handle the permission request result. If the permission is granted, proceed with using the scanner. Otherwise, display a toast message informing the user that the camera permission is required to use the app.

Testing the Code Scanner

Once you have implemented all the required functions and set up the layout, you can test the QR code scanner. Run the app on a device or emulator that has a camera. The app will prompt you to grant camera permission. Upon granting the permission, the camera will be activated, and you can start scanning QR codes and barcodes by aligning them within the scanner view. The result will be displayed in the text view below the scanner.

Conclusion

In this tutorial, we learned how to create a QR code scanner in Android using Kotlin. We used the Code Scanner library to implement the functionality and added features like autofocus, flashlight control, and a user-friendly interface. By following the step-by-step instructions, you should now have a working QR code scanner in your Android app.

Highlights:

• Create a QR code scanner in Android using Kotlin.
• Use the Code Scanner library by Yuri Budiev for decoding QR codes and barcodes.
• Add camera runtime permission and handle permission requests.
• Design a user-friendly layout for the QR code scanner.
• Implement autofocus, flashlight control, and continuous scanning functionality.
• Test the app by scanning QR codes and barcodes.

FAQ:

Q: Can I use this QR code scanner with any Android device? A: Yes, you can use this QR code scanner with any Android device that has a camera. However, devices running on API level 23 and above require runtime permission for accessing the camera.

Q: Can I customize the UI of the QR code scanner? A: Yes, you can customize the UI of the QR code scanner by modifying the activity_main.xml layout file. You can change the size, position, and colors of the scanner view and other UI elements.

Q: Can I scan both QR codes and barcodes with this QR code scanner? A: Yes, this QR code scanner can scan both QR codes and barcodes. It is compatible with various barcode formats, and you can specify which formats to scan if needed.

Q: Is it possible to use the flash feature while scanning QR codes? A: Yes, you can use the flash feature while scanning QR codes by enabling the flashlight button in the UI. This allows you to scan codes in low-light conditions.

Q: What happens if the user denies the camera permission? A: If the user denies the camera permission, they will not be able to use the QR code scanner functionality. The app will display a message informing the user that the camera permission is required to use the app. To give the permission, the user will need to close and reopen the app.

Q: Can I further customize the behavior of the QR code scanner? A: Yes, you can customize the behavior of the QR code scanner by modifying the code in the MainActivity.kt file. You can add additional callbacks, change the scanning mode, or modify the error handling logic based on your requirements.

Q: Is the QR code scanner compatible with Kotlin and Java? A: Yes, the QR code scanner is compatible with both Kotlin and Java. The Code Scanner library provides usage examples in both languages, allowing you to choose the one you are comfortable with.