我将扫描仪设为黑屏而不是相机

Question

我试图在我的应用程序中创建条形码扫描仪。但是它没有显示相机，它在上周显示了黑屏，但仍然可以使用。我该如何解决。我的代码在这里

public class ScanBarcodeCartActivity extends AppCompatActivity {

private SurfaceView surfaceView;
private CameraSource cameraSource;
private TextView text_code,re_scan;
private Button btn_confirm_cart;
private BarcodeDetector barcodeDetector;

private String id_order;
private String phone;
private String cart,dateid,date;

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

    surfaceView = findViewById(R.id.camera_preview);
    text_code = findViewById(R.id.text_code);
    btn_confirm_cart = findViewById(R.id.confirm_cart);
    re_scan = findViewById(R.id.re_scan);

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

    cameraSource = new CameraSource.Builder(this,barcodeDetector)
        .setRequestedPreviewSize(640,480).setAutoFocusEnabled(true).build();


    surfaceView.getHolder().addCallback(new SurfaceHolder.Callback() {
        @Override
        public void surfaceCreated(SurfaceHolder holder) {
            if (ActivityCompat.checkSelfPermission(getApplicationContext(), Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {
                return;
            }
            try {
                cameraSource.start(holder);
            }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() {

        }

        @Override
        public void receiveDetections(Detector.Detections<Barcode> detections) {
            final SparseArray<Barcode> qrcode = detections.getDetectedItems();

            if (qrcode.size() != 0) {
                text_code.post(new Runnable() {
                    @Override
                    public void run() {
                        text_code.setText(qrcode.valueAt(0).displayValue);
                    }
                });
            }
        }
    });

}    }

我尝试了许多方法，但仍然不能。 我不知道是因为相机还是表面视图。 并感谢您的建议。