public void setTorch(final boolean on) {
        Util.validateMainThread();

        if (open) {
            cameraThread.enqueue(() -> cameraManager.setTorch(on));
        }
    }
@return the camera rotation relative to display rotation, in degrees. Typically 0 if the
   display is in landscape orientation.
zxing-android-embedded/src/com/journeyapps/barcodescanner/camera/CameraInstance.java