private void initialiseDetectorsAndSources()
    {
        String str="";

        Toast.makeText(getApplicationContext(), "Barcode scanner started", Toast.LENGTH_SHORT).show();

        barcodeDetector = new BarcodeDetector.Builder(this)
                .setBarcodeFormats(Barcode.ALL_FORMATS)
                .build();

        cameraSource = new CameraSource.Builder(this, barcodeDetector)
                .setRequestedPreviewSize(1920, 1080)
                .setAutoFocusEnabled(true) //you should add this feature
                .build();

       
        surfaceView.getHolder().addCallback(new SurfaceHolder.Callback()
        {
            @Override
            public void surfaceCreated(SurfaceHolder holder)
            {
                try
                {
                    if (ActivityCompat.checkSelfPermission(ScannerBarcodeActivity.this, Manifest.permission.CAMERA) == PackageManager.PERMISSION_GRANTED)
                    {
                        cameraSource.start(surfaceView.getHolder());
                    }
                    else
                    {
                        ActivityCompat.requestPermissions(ScannerBarcodeActivity.this, new
                                String[]{Manifest.permission.CAMERA}, REQUEST_CAMERA_PERMISSION);
                    }

                } catch (IOException e)
                {
                    e.printStackTrace();
                }
            }

            @Override
            public void surfaceChanged(SurfaceHolder holder, int format, int width, int height)
            {

            }

            @Override
            public void surfaceDestroyed(SurfaceHolder holder)
            {
                cameraSource.stop();
            }
        });

        barcodeDetector.setProcessor(new Detector.Processor<Barcode>()
        {
            @Override
            public void release()
            {
                Toast.makeText(getApplicationContext(), "To prevent memory leaks barcode scanner has been stopped", Toast.LENGTH_SHORT).show();
            }

            @Override
            public void receiveDetections(Detector.Detections<Barcode> detections)
            {
                final SparseArray<Barcode> barcodes = detections.getDetectedItems();
                if (barcodes.size() != 0)
                {
                    String str= barcodes.valueAt(0).displayValue; /**scanned code*/
                    TextView txt= (TextView) findViewById(R.id.txtBarcodeValue);
                    txt.setText(str);

                    Toast.makeText(ScannerBarcodeActivity.this, str, Toast.LENGTH_LONG).show(); 
                }
            }
        });
    }