Create and Scan QRCode in Android

Create new project in Android Studio with steps as below:

Open res\values\strings.xml file and add new string as below:

<resources>
    <string name="app_name">Learn Android with Real Apps</string>
    <string name="product_id">Enter Product Id</string>
    <string name="generate">Generate</string>
    <string name="scan">Scan</string>
</resources>

Open build.gradle file in Gradle Scripts and add new library as below:

implementation 'com.google.zxing:core:3.2.1'
implementation 'com.journeyapps:zxing-android-embedded:3.2.0@aar'

Open res\layout\activity_main.xml file and create layout as below:

<?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="fill_parent"
    android:layout_height="fill_parent"
    android:background="#ffffff"
    android:orientation="vertical"
    tools:ignore="HardcodedText">

    <EditText
        android:id="@+id/editTextProductId"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:ems="10"
        android:hint="@string/product_id"
        android:inputType="textPersonName" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">

        <Button
            android:id="@+id/buttonGenerate"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="@string/generate" />

        <Button
            android:id="@+id/buttonScan"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="@string/scan" />
    </LinearLayout>

    <ImageView
        android:id="@+id/imageViewResult"
        android:layout_width="match_parent"
        android:layout_height="335dp" />

</LinearLayout>

Add code to MainActivity.java file in android.demo.learnandroidwithrealapps package as below:

package android.demo.learnandroidwithrealapps;

import android.content.Intent;
import android.graphics.Bitmap;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.Toast;

import com.google.zxing.BarcodeFormat;
import com.google.zxing.MultiFormatWriter;
import com.google.zxing.common.BitMatrix;
import com.google.zxing.integration.android.IntentIntegrator;
import com.google.zxing.integration.android.IntentResult;
import com.journeyapps.barcodescanner.BarcodeEncoder;

public class MainActivity extends AppCompatActivity {

    private EditText editTextProductId;
    private Button buttonGenerate, buttonScan;
    private ImageView imageViewResult;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initView();
    }

    private void initView() {
        editTextProductId = findViewById(R.id.editTextProductId);
        imageViewResult = findViewById(R.id.imageViewResult);
        buttonGenerate = findViewById(R.id.buttonGenerate);
        buttonGenerate.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                buttonGenerate_onClick(view);
            }
        });
        buttonScan = findViewById(R.id.buttonScan);
        buttonScan.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                buttonScan_onClick(view);
            }
        });
    }

    private void buttonGenerate_onClick(View view) {
        try {
            String productId = editTextProductId.getText().toString();
            MultiFormatWriter multiFormatWriter = new MultiFormatWriter();
            BitMatrix bitMatrix = multiFormatWriter.encode(productId, BarcodeFormat.QR_CODE, 400, 400);
            BarcodeEncoder barcodeEncoder = new BarcodeEncoder();
            Bitmap bitmap = barcodeEncoder.createBitmap(bitMatrix);
            imageViewResult.setImageBitmap(bitmap);
        } catch (Exception e) {
            Toast.makeText(getApplicationContext(), e.getMessage(), Toast.LENGTH_LONG).show();
        }
    }

    private void buttonScan_onClick(View view) {
        IntentIntegrator intentIntegrator = new IntentIntegrator(this);
        intentIntegrator.setDesiredBarcodeFormats(IntentIntegrator.QR_CODE_TYPES);
        intentIntegrator.setCameraId(0);
        intentIntegrator.initiateScan();
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        IntentResult intentResult = IntentIntegrator.parseActivityResult(requestCode, resultCode, data);
        if(intentResult != null) {
            String productId = intentResult.getContents();
            Toast.makeText(getApplicationContext(), productId, Toast.LENGTH_LONG).show();
        }
    }

}