in  build.gradle(:app)


// QR Scan
implementation 'com.journeyapps:zxing-android-embedded:4.3.0'


in MainActivity.Java

Create button and set on click listener, Call a method scanCode();

btnConfirmReceived.setOnClickListener(view -> {
     scanCode();
});

private void scanCode() {
    
    ScanOptions options = new ScanOptions();
    options.setPrompt("Volume up to flash on");
    options.setBeepEnabled(true);
    options.setOrientationLocked(true);
    options.setCaptureActivity(CaptureAct.class);
    barLauncher.launch(options);

}

ActivityResultLauncher<ScanOptions> barLauncher = registerForActivityResult(new ScanContract(), result -> {

    if(result.getContents() != null){
        AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);
        builder.setTitle("Result");
        builder.setMessage(result.getContents());
        builder.setPositiveButton("Ok", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialogInterface, int i) {
                dialogInterface.dismiss();
            }
        }).show();
    }

});

create class CaptureAct.java


public class CaptureAct extends CaptureActivity {
}

in AndroidManifest.xml


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

<activity android:name=".CaptureAct"
    android:screenOrientation="portrait"
    android:stateNotNeeded="true"
    android:theme="@style/zxing_CaptureTheme"/>