private void InitScan()
        {
            var integrator = new IntentIntegrator(this);

            integrator.SetPrompt("请扫描");
            integrator.SetOrientationLocked(true);
            integrator.SetCameraId(0);
            integrator.SetBeepEnabled(false);
            integrator.SetCaptureActivity(new ScanActivity().Class);
            integrator.InitiateScan();
        }