How to Build a QR Code Android App using Firebase?

Last Updated : 24 Apr, 2025

QR (Quick Response) code is a type of two-dimensional barcode that contains information encoded in a pattern of black and white squares. It was first developed in 1994 by a company named Denso Wave. Qr codes can be scanned by a smartphone or a dedicated QR code scanner, which uses the device's camera to read the code and extract the information stored within it. This can include text, URLs, contact information, and more, depending on what the QR code has been programmed to contain. A sample video is given below to get an idea about what we are going to do in this article.

Note: This Android article covered in both Java and Kotlin languages.

QR Scanner

A QR Scanner is a tool that can read and decode QR codes. QR code scanners are widely available as mobile apps that can be downloaded on smartphones and tablets and can be used to scan QR codes using the device's built-in camera. Our QR code scanner app also includes additional features, such as the ability to generate QR codes and share information with others.

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 Java as the programming language.

Step 2:

Create two floating buttons, one for scanning the code and the other for generating the QR code.

QR Generator Code:

XML

<?xml version="1.0" encoding="utf-8"?> <layer-list xmlns:android="http://schemas.android.com/apk/res/android">     <item>         <shape             android:shape="oval">             <gradient                 android:startColor="#FDDC74"                 android:endColor="#FBD665">             </gradient>         </shape>     </item>      <item android:gravity="center">         <vector android:height="24dp" android:tint="#FFFFFF"             android:viewportHeight="24" android:viewportWidth="24"             android:width="24dp" xmlns:android="http://schemas.android.com/apk/res/android">             <path android:fillColor="@android:color/white" android:pathData="M3,11h8V3H3V11zM5,5h4v4H5V5z"/>             <path android:fillColor="@android:color/white" android:pathData="M3,21h8v-8H3V21zM5,15h4v4H5V15z"/>             <path android:fillColor="@android:color/white" android:pathData="M13,3v8h8V3H13zM19,9h-4V5h4V9z"/>             <path android:fillColor="@android:color/white" android:pathData="M19,19h2v2h-2z"/>             <path android:fillColor="@android:color/white" android:pathData="M13,13h2v2h-2z"/>             <path android:fillColor="@android:color/white" android:pathData="M15,15h2v2h-2z"/>             <path android:fillColor="@android:color/white" android:pathData="M13,17h2v2h-2z"/>             <path android:fillColor="@android:color/white" android:pathData="M15,19h2v2h-2z"/>             <path android:fillColor="@android:color/white" android:pathData="M17,17h2v2h-2z"/>             <path android:fillColor="@android:color/white" android:pathData="M17,13h2v2h-2z"/>             <path android:fillColor="@android:color/white" android:pathData="M19,15h2v2h-2z"/>         </vector>      </item> </layer-list>

QR Scanner Code:

XML

<?xml version="1.0" encoding="utf-8"?> <layer-list xmlns:android="http://schemas.android.com/apk/res/android"> <item>     <shape         android:shape="oval">         <gradint             android:startColor="#43DAA6"             android:endColor="#09855C">         </gradint>     </shape> </item>      <item android:gravity="center">          <vector android:height="24dp" android:tint="#FFFFFF"             android:viewportHeight="24" android:viewportWidth="24"             android:width="24dp" xmlns:android="http://schemas.android.com/apk/res/android">             <path android:fillColor="@android:color/white" android:pathData="M7,3H4v3H2V1h5V3zM22,6V1h-5v2h3v3H22zM7,21H4v-3H2v5h5V21zM20,18v3h-3v2h5v-5H20zM19,18c0,1.1 -0.9,2 -2,2H7c-1.1,0 -2,-0.9 -2,-2V6c0,-1.1 0.9,-2 2,-2h10c1.1,0 2,0.9 2,2V18zM15,8H9v2h6V8zM15,11H9v2h6V11zM15,14H9v2h6V14z"/>         </vector>     </item> </layer-list>

Output UI:

Step 3:

Add a gradient to your background.

XML

<?xml version="1.0" encoding="utf-8"?> <selector xmlns:android="http://schemas.android.com/apk/res/android">     <item>         <shape             android:shape="rectangle">             <gradient                 android:startColor="#615EE8"                 android:endColor="#7F6CEF"/>         </shape>     </item> </selector>

Step 4:

In your activity main xml file add one CardView, one ImageView, two floating action buttons, and one EditText.

XML

<?xml version="1.0" encoding="utf-8"?> <LinearLayout      xmlns:android="http://schemas.android.com/apk/res/android"     xmlns:app="http://schemas.android.com/apk/res-auto"     xmlns:tools="http://schemas.android.com/tools"     android:layout_width="match_parent"     android:layout_height="match_parent"     android:orientation="vertical"     android:background="@drawable/back_qr"     android:gravity="center_horizontal"     tools:context=".MainActivity">      <TextView         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:text="MY QR CODE"         android:textSize="24sp"         android:textStyle="bold"         android:fontFamily="@font/bold"         android:textColor="@color/white"         android:layout_marginTop="50dp"/>      <androidx.cardview.widget.CardView         android:layout_marginTop="35dp"         android:layout_width="290dp"         android:layout_height="350dp"         app:cardCornerRadius="25dp">                <ImageView             android:id="@+id/img_qr"             android:layout_width="match_parent"             android:layout_height="match_parent"             android:scaleType="fitCenter">         </ImageView>            </androidx.cardview.widget.CardView>      <androidx.cardview.widget.CardView         android:layout_width="300dp"         android:layout_height="80dp"         android:layout_marginTop="20dp"         app:cardCornerRadius="50dp"         android:backgroundTint="#5754D3">         <RelativeLayout             android:layout_width="wrap_content"             android:layout_height="wrap_content">                        <com.google.android.material.floatingactionbutton.FloatingActionButton                 android:layout_width="43dp"                 android:layout_height="43dp"                 android:id="@+id/btnQr"                 android:layout_marginLeft="17dp"                 android:layout_marginTop="20dp"                 style="@style/floating_yellow">             </com.google.android.material.floatingactionbutton.FloatingActionButton>                        <TextView                 android:layout_width="wrap_content"                 android:layout_height="wrap_content"                 android:layout_marginTop="15dp"                 android:text="Generate Your Qr Code"                 android:layout_marginLeft="80dp"                 android:textColor="@color/white"                 android:textStyle="bold"                 android:fontFamily="@font/bold"                 android:textSize="16sp">             </TextView>                  <EditText                     android:id="@+id/edtgen"                     android:layout_width="wrap_content"                     android:layout_height="wrap_content"                     android:hint="Enter your Section Here"                     android:background="@null"                     android:layout_marginTop="45dp"                     android:layout_marginLeft="80dp"                     android:textColor="@color/white"                     android:textColorHint="@color/white"                     android:textSize="12sp" />         </RelativeLayout>      </androidx.cardview.widget.CardView>      <com.google.android.material.floatingactionbutton.FloatingActionButton         android:id="@+id/btnScan"         android:layout_width="50dp"         android:layout_height="50dp"         style="@style/floating_green"         android:layout_marginTop="60dp"         android:outlineSpotShadowColor="@color/black"         android:outlineAmbientShadowColor="@color/black"/>  </LinearLayout>

Step 5:

In your main activity add this code, and create two onclick Listeners for generating and scanning the QR code.

Java

package com.shruti.qrcodescanner;  import androidx.appcompat.app.AppCompatActivity; import androidx.cardview.widget.CardView;  import android.annotation.SuppressLint; import android.content.Context; import android.content.Intent; import android.graphics.Bitmap; import android.media.Image; import android.os.Bundle; import android.view.View; import android.view.inputmethod.InputMethod; import android.view.inputmethod.InputMethodManager; import android.widget.Button; import android.widget.EditText; import android.widget.ImageView; import android.widget.RelativeLayout; import android.widget.TextView;  import com.google.android.material.floatingactionbutton.FloatingActionButton; import com.google.zxing.BarcodeFormat; import com.google.zxing.MultiFormatWriter; import com.google.zxing.WriterException; import com.google.zxing.common.BitMatrix; import com.journeyapps.barcodescanner.BarcodeEncoder;  public class MainActivity extends AppCompatActivity {        FloatingActionButton btnQr;     FloatingActionButton btnScan;     EditText edtgen;     ImageView img_qr;        @SuppressLint("WrongViewCast")     @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.activity_main);          btnScan =(FloatingActionButton) findViewById(R.id.btnScan);         btnQr =  (FloatingActionButton)findViewById(R.id.btnQr);         edtgen = (EditText) findViewById(R.id.edtgen);         img_qr = (ImageView) findViewById(R.id.img_qr);          btnScan.setOnClickListener(new View.OnClickListener() {             @Override             public void onClick(View v) {                 startActivity(new Intent(getApplicationContext(),qrScanner.class));             }         });          btnQr.setOnClickListener(new View.OnClickListener() {             @Override             public void onClick(View v) {                 String Gqr = edtgen.getText().toString().trim();                 MultiFormatWriter writer = new MultiFormatWriter();                  try {                     BitMatrix matrix = writer.encode(Gqr, BarcodeFormat.QR_CODE,                             260,320);                     BarcodeEncoder encoder = new BarcodeEncoder();                     Bitmap bitmap = encoder.createBitmap(matrix);                     img_qr.setImageBitmap(bitmap);                     InputMethodManager manager = (InputMethodManager)getSystemService(                             Context.INPUT_METHOD_SERVICE                     );                     manager.hideSoftInputFromWindow(edtgen.getApplicationWindowToken(),                             0);                 } catch (WriterException e) {                     e.printStackTrace();                 }             }         });      } }

Kotlin

package com.shruti.qrcodescanner  import android.content.Context import android.content.Intent import android.graphics.Bitmap import android.os.Bundle import android.view.View import android.view.inputmethod.InputMethodManager import androidx.appcompat.app.AppCompatActivity import com.google.android.material.floatingactionbutton.FloatingActionButton import com.google.zxing.BarcodeFormat import com.google.zxing.MultiFormatWriter import com.google.zxing.WriterException import com.google.zxing.common.BitMatrix import com.journeyapps.barcodescanner.BarcodeEncoder import kotlinx.android.synthetic.main.activity_main.*  class MainActivity : AppCompatActivity() {      override fun onCreate(savedInstanceState: Bundle?) {         super.onCreate(savedInstanceState)         setContentView(R.layout.activity_main)          val btnScan = findViewById<FloatingActionButton>(R.id.btnScan)         val btnQr = findViewById<FloatingActionButton>(R.id.btnQr)         val edtgen = findViewById<EditText>(R.id.edtgen)         val img_qr = findViewById<ImageView>(R.id.img_qr)          btnScan.setOnClickListener {             startActivity(Intent(applicationContext, qrScanner::class.java))         }          btnQr.setOnClickListener {             val Gqr = edtgen.text.toString().trim()             val writer = MultiFormatWriter()              try {                 val matrix: BitMatrix = writer.encode(                     Gqr,                     BarcodeFormat.QR_CODE,                     260,                     320                 )                 val encoder = BarcodeEncoder()                 val bitmap: Bitmap = encoder.createBitmap(matrix)                 img_qr.setImageBitmap(bitmap)                 val manager = getSystemService(Context.INPUT_METHOD_SERVICE) as InputMethodManager                 manager.hideSoftInputFromWindow(edtgen.applicationWindowToken, 0)             } catch (e: WriterException) {                 e.printStackTrace()             }         }     } }

Step 6:

Create a new Empty activity in your project. Add this code to your Java folder.

Java

package com.shruti.qrcodescanner;  import android.os.Bundle; import android.Manifest;  import androidx.annotation.NonNull; import androidx.appcompat.app.AppCompatActivity;  import com.google.android.gms.tasks.OnCompleteListener; import com.google.android.gms.tasks.Task; import com.google.firebase.database.DatabaseReference; import com.google.firebase.database.FirebaseDatabase; import com.google.zxing.Result; import com.karumi.dexter.Dexter; import com.karumi.dexter.PermissionToken; import com.karumi.dexter.listener.PermissionDeniedResponse; import com.karumi.dexter.listener.PermissionGrantedResponse; import com.karumi.dexter.listener.PermissionRequest; import com.karumi.dexter.listener.single.PermissionListener;  import me.dm7.barcodescanner.zxing.ZXingScannerView;  public class qrScanner extends AppCompatActivity implements ZXingScannerView.ResultHandler {     ZXingScannerView scannerView;     DatabaseReference dref ;      @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         scannerView= new ZXingScannerView(this);         setContentView(scannerView);         dref = FirebaseDatabase.getInstance().getReference("information");         Dexter.withContext(getApplicationContext())                 .withPermission(Manifest.permission.CAMERA)                 .withListener(new PermissionListener() {                     @Override                     public void onPermissionGranted(PermissionGrantedResponse permissionGrantedResponse) {                         scannerView.startCamera();                     }                      @Override                     public void onPermissionDenied(PermissionDeniedResponse permissionDeniedResponse) {                      }                      @Override                     public void onPermissionRationaleShouldBeShown(PermissionRequest permissionRequest, PermissionToken permissionToken) {                         permissionToken.continuePermissionRequest();                     }                 }).check();     }       @Override     public void handleResult(Result rawResult) {         String data = rawResult.getText().toString();          dref.push().setValue(data)                 .addOnCompleteListener(new OnCompleteListener<Void>() {                     @Override                     public void onComplete(@NonNull Task<Void> task) {                         onBackPressed();                     }                 });     }      @Override     protected void onPause() {         super.onPause();         scannerView.stopCamera();     }      @Override     protected void onResume() {         super.onResume();         scannerView.setResultHandler(this);         scannerView.startCamera();     } }

Kotlin

package com.shruti.qrcodescanner  import android.Manifest import android.os.Bundle import androidx.appcompat.app.AppCompatActivity import com.google.android.gms.tasks.OnCompleteListener import com.google.android.gms.tasks.Task import com.google.firebase.database.DatabaseReference import com.google.firebase.database.FirebaseDatabase import com.google.zxing.Result import com.karumi.dexter.Dexter import com.karumi.dexter.PermissionToken import com.karumi.dexter.listener.PermissionDeniedResponse import com.karumi.dexter.listener.PermissionGrantedResponse import com.karumi.dexter.listener.PermissionRequest import com.karumi.dexter.listener.single.PermissionListener import me.dm7.barcodescanner.zxing.ZXingScannerView  class qrScanner : AppCompatActivity(), ZXingScannerView.ResultHandler {     private lateinit var scannerView: ZXingScannerView     private lateinit var dref: DatabaseReference      override fun onCreate(savedInstanceState: Bundle?) {         super.onCreate(savedInstanceState)         scannerView = ZXingScannerView(this)         setContentView(scannerView)         dref = FirebaseDatabase.getInstance().getReference("information")         Dexter.withContext(applicationContext)             .withPermission(Manifest.permission.CAMERA)             .withListener(object : PermissionListener {                 override fun onPermissionGranted(permissionGrantedResponse: PermissionGrantedResponse) {                     scannerView.startCamera()                 }                  override fun onPermissionDenied(permissionDeniedResponse: PermissionDeniedResponse) {}                  override fun onPermissionRationaleShouldBeShown(                     permissionRequest: PermissionRequest,                     permissionToken: PermissionToken                 ) {                     permissionToken.continuePermissionRequest()                 }             }).check()     }      override fun handleResult(rawResult: Result) {         val data = rawResult.text          dref.push().setValue(data)             .addOnCompleteListener { task: Task<Void?> ->                 onBackPressed()             }     }      override fun onPause() {         super.onPause()         scannerView.stopCamera()     }      override fun onResume() {         super.onResume()         scannerView.setResultHandler(this)         scannerView.startCamera()     } }

Step 7:

Add these dependencies in your gradle file.

implementation 'me.dm7.barcodescanner:zxing:1.9.13'
implementation 'com.karumi:dexter:6.2.2'
implementation 'com.journeyapps:zxing-android-embedded:3.4.0'

Step 8:

Add these styles to your themes.xml.

XML

<style>     <style name="CardView." parent="CardView">         <item name ="android:foreground">@drawable/button_grad</item>     </style>     <style name="floating_yellow" parent="Widget.Design.FloatingActionButton">         <item name="android:foreground">@drawable/qr_button</item>     </style>     <style name="floating_green" parent="Widget.Design.FloatingActionButton">         <item name="android:foreground">@drawable/scan_button</item> </style>