Web scraping is technique of extracting information from websites. For mobile applications, it should be considered a last resort. Instead try to get access to the inderlying data via a documented REST web service API.
However, you may find that an REST or SOAP API is not available and you may need to web scrape in order to get the web site data into your mobile application.
If you are going web scrape, then don't do it in the mobile app. Instead, use a microservices platform, like Arrow. By implementing the screen scraping in an Arrow middle tier server, then when the web site changes, you can change your scraping algorithm without needing to publish a new mobile application.
This blog post will show a simple example of using Arrow Builder to build an API that utilizes web scraping.