Generate QR Code in Android using Kotlin

Many applications nowadays use QR codes within their application to hide some information. QR codes are seen within many payment applications which are used by the users to scan and make payments. The QR codes which are seen within these applications are generated inside the application itself. In this article, we will take a look at How to generate a QR code in Android using Kotlin. A sample video is given below to get an idea about what we are going to do in this article.

Note: If you are looking to generate QR code in android using Java. Check out the following article: How to Generate QR Code in Android using Java

Step by Step Implementation

Step 1: Create a New Project in Android Studio

To create a new project in Android Studio please refer to How to Create/Start a New Project in Android Studio. Note that select Kotlin as the programming language.

Step 2: Add dependency to build.gradle(Module:app)

Navigate to the Gradle Scripts > build.gradle(Module:app) and add the below dependency in the dependencies section.

implementation 'androidmads.library.qrgenerator:QRGenerator:1.0.3'

After adding this dependency simply sync this project to install it. 

Step 3: Working with the activity_main.xml file

Navigate to the app > res > layout > activity_main.xml and add the below code to that file. Below is the code for the activity_main.xml file. Comments are added inside the code to understand the code in more detail.

XML

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <!--on below line we are creating
        a text for heading of our app-->
    <TextView
        android:id="@+id/idTVHeading"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="8dp"
        android:gravity="center"
        android:padding="4dp"
        android:text="QR Code Generator"
        android:textAlignment="center"
        android:textColor="@color/purple_200"
        android:textSize="18sp"
        android:textStyle="bold" />

    <!--We are using this image
        view to display our QR code-->
    <ImageView
        android:id="@+id/idIVQrcode"
        android:layout_width="300dp"
        android:layout_height="300dp"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="50dp"
        android:contentDescription="QR Code" />

    <!--Edit text to enter text
        for creating a QR code-->
    <EditText
        android:id="@+id/idEdt"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/idIVQrcode"
        android:layout_marginStart="20dp"
        android:layout_marginTop="30dp"
        android:layout_marginEnd="20dp"
        android:autofillHints=""
        android:hint="Enter your message"
        android:inputType="text" />

    <!--Button for creating a QR code-->
    <Button
        android:id="@+id/idBtnGenerateQR"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/idEdt"
        android:layout_marginStart="20dp"
        android:layout_marginTop="30dp"
        android:layout_marginEnd="20dp"
        android:text="Generate QR Code"
        android:textAllCaps="false" />

</RelativeLayout>

Step 4: Working with the MainActivity.kt file

Go to the MainActivity.kt file and refer to the following code. Below is the code for the MainActivity.kt file. Comments are added inside the code to understand the code in more detail.

Kotlin

package com.gtappdevelopers.kotlingfgproject

import android.graphics.Bitmap
import android.graphics.Point
import android.os.Bundle
import android.text.TextUtils
import android.view.Display
import android.view.WindowManager
import android.widget.Button
import android.widget.EditText
import android.widget.ImageView
import android.widget.Toast
import androidmads.library.qrgenerator.QRGContents
import androidmads.library.qrgenerator.QRGEncoder
import androidx.appcompat.app.AppCompatActivity

class MainActivity : AppCompatActivity() {

    // on below line we are creating a variable
    // for our image view, edit text and a button.
    lateinit var qrIV: ImageView
    lateinit var msgEdt: EditText
    lateinit var generateQRBtn: Button

    // on below line we are creating
    // a variable for bitmap
    lateinit var bitmap: Bitmap

    // on below line we are creating
    // a variable for qr encoder.
    lateinit var qrEncoder: QRGEncoder

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        // on below line we are
        // initializing our all variables.
        qrIV = findViewById(R.id.idIVQrcode)
        msgEdt = findViewById(R.id.idEdt)
        generateQRBtn = findViewById(R.id.idBtnGenerateQR)

        // on below line we are adding on click
        // listener for our generate QR button.
        generateQRBtn.setOnClickListener {
            // on below line we are checking if msg edit text is empty or not.
            if (TextUtils.isEmpty(msgEdt.text.toString())) {

                // on below line we are displaying toast message to display enter some text
                Toast.makeText(applicationContext, "Enter your message", Toast.LENGTH_SHORT).show()
            } else {
                // on below line we are getting service for window manager
                val windowManager: WindowManager = getSystemService(WINDOW_SERVICE) as WindowManager

                // on below line we are initializing a
                // variable for our default display
                val display: Display = windowManager.defaultDisplay

                // on below line we are creating a variable
                // for point which is use to display in qr code
                val point: Point = Point()
                display.getSize(point)

                // on below line we are getting
                // height and width of our point
                val width = point.x
                val height = point.y

                // on below line we are generating
                // dimensions for width and height
                var dimen = if (width < height) width else height
                dimen = dimen * 3 / 4

                // on below line we are initializing our qr encoder
                qrEncoder = QRGEncoder(msgEdt.text.toString(), null, QRGContents.Type.TEXT, dimen)

                // on below line we are running a try
                // and catch block for initializing our bitmap
                try {
                    // on below line we are
                    // initializing our bitmap
                    bitmap = qrEncoder.encodeAsBitmap()

                    // on below line we are setting
                    // this bitmap to our image view
                    qrIV.setImageBitmap(bitmap)
                } catch (e: Exception) {
                    // on below line we
                    // are handling exception
                    e.printStackTrace()
                }
            }
        }
    }
}

Now run your application to see the output of it. 

Output: