CameraSource is stretched in AlertDialog

I'm using SurfaceView in my AlertDialog in which i show a CameraSource which then scans barcodes, my main issue is that the camera preview is distort and stretched at the left and right.

The function where i initialize the CameraSource and SurfaceHolder looks like this:

private void initializeBarcodeReader(SurfaceView surfaceView, boolean greenpass) {
    ToneGenerator toneGen = new ToneGenerator(AudioManager.STREAM_MUSIC, 100);
    BarcodeDetector barcodeDetector = new BarcodeDetector.Builder(this)
            .setBarcodeFormats(greenpass ? Barcode.QR_CODE : Barcode.ALL_FORMATS)
            .build();
    CameraSource cameraSource = new CameraSource.Builder(this, barcodeDetector)
            .setAutoFocusEnabled(true)
            .build();

    SurfaceHolder previewHolder = surfaceView.getHolder();
    previewHolder.addCallback(new SurfaceHolder.Callback() {
        @Override
        public void surfaceCreated(SurfaceHolder holder) {
            try {
                if (ActivityCompat.checkSelfPermission(PtermActivity.this, Manifest.permission.CAMERA) == PackageManager.PERMISSION_GRANTED) {
                    cameraSource.start(holder);
                } else {
                    ActivityCompat.requestPermissions(PtermActivity.this, new
                            String[]{Manifest.permission.CAMERA}, 201);
                }
            } catch (IOException e) {
                e.printStackTrace();
            }


        }

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

        @Override
        public void surfaceDestroyed(SurfaceHolder holder) {
            if (cameraSource != null) {
                cameraSource.stop();
                cameraSource.release();
            }
        }
    });
    previewHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
}

But the preview is as the following:

As you could see the pen is very stretched as the phone behind, the preview is not as the one in the real Camera app...

How could i fix it?