Mobile vision is not detecting QR codes

Question

I'm trying to add QR code scanning functionality to my application. I've used google vision to detect the QR codes. But, it fails to detect the codes. Even though the Detector.isOperational() returns true but nothing happening. I guess the preview quality is pretty dumb to scan the QR that's why it is failing. The codes as follow. THANK YOU.

package com.example.tngrocery;

import androidx.appcompat.app.AppCompatActivity;

   import android.graphics.SurfaceTexture;

   import android.hardware.Camera;

   import android.os.Bundle;

   import android.util.SparseArray;

   import android.view.Gravity;

   import android.view.TextureView;

   import android.widget.TextView;

   import android.widget.Toast;

   import com.google.android.gms.vision.Detector;

   import com.google.android.gms.vision.barcode.Barcode;

   import com.google.android.gms.vision.barcode.BarcodeDetector;

   public class ScanQR extends AppCompatActivity implements TextureView.SurfaceTextureListener{

TextureView textureView;

   TextureView textureView;

   TextView displayResult;

   BarcodeDetector detector;

   @Override

   protected void onCreate(Bundle savedInstanceState) {

   super.onCreate(savedInstanceState);

   setContentView(R.layout.activity_scan_q_r);

   displayResult = findViewById(R.id.alignQR);

   textureView = findViewById(R.id.texture_view);

   textureView.setSurfaceTextureListener(this);

   detector = new BarcodeDetector.Builder(this).

   setBarcodeFormats(Barcode.QR_CODE).

   build();

   try {

   if (detector.isOperational()) {

   displayResult.setText("it works");

   } else {

   displayResult.setText("Nope");

   }

   }

   catch (Exception e){

   Toast test = Toast.makeText(this,e.toString(),Toast.LENGTH_LONG);

   test.setGravity(Gravity.TOP|Gravity.LEFT, 0, 0);



test.show();
    }

   }

       @Override


       public void onSurfaceTextureAvailable(SurfaceTexture surface, int width, int height) {

       try{

       cam = Camera.open();

       test.show();


   }

   @Override

   public void onSurfaceTextureAvailable(SurfaceTexture surface, int width, int height) {

   try{

   cam = Camera.open();

   cam.setPreviewTexture(surface);

   cam.setDisplayOrientation(90);

   cam.startPreview();

   detector.setFocus(1);

   detector.setProcessor(new Detector.Processor<Barcode>(){

   @Override

   public void release() {

   }

   @Override

   public void receiveDetections(Detector.Detections<Barcode> detections) {

   final SparseArray<Barcode> barcodes = detections.getDetectedItems();

   if(barcodes.size() != 0){

   displayResult.post(new Runnable() {

   @Override

       public void run() {

   displayResult.setText(barcodes.valueAt(0).displayValue);

   }

   });

   }

   }

   });

   }

   catch(Exception camException){

   Toast.makeText(this,camException.toString(),Toast.LENGTH_LONG).show();

   }

   }

   @Override

   public void onSurfaceTextureSizeChanged(SurfaceTexture surface, int width, int height) {

   }

   @Override

   public boolean onSurfaceTextureDestroyed(SurfaceTexture surface) {

   cam.stopPreview();

   return false;

   }

   @Override

   public void onSurfaceTextureUpdated(SurfaceTexture surface) {

    }

}