public ScanOptions setCameraId(int cameraId) {
        if (cameraId >= 0) {
            addExtra(Intents.Scan.CAMERA_ID, cameraId);
        }
        return this;
    }
Use the specified camera ID.

@param cameraId camera ID of the camera to use. A negative value means "no preference".
@return this
zxing-android-embedded/src/com/journeyapps/barcodescanner/ScanOptions.java