Application classes are the primary means to initialize, add business logic, and dynamically change layouts for Mobile Application Platform applications.
The Mobile Application Platform framework completely separates the business logic from the presentation layer. All Mobile Application Platform metadata is available in the application class PeopleCode layer and is not tied to application pages or other metadata, allowing you to override the defaults defined on the actual layout. This means that you have complete control of the presentation layer for any transaction within the application class PeopleCode.
PeopleSoft delivers two Mobile Application Platform application interface class methods that enable you to manipulate pages, elements, and other aspects of your applications via PeopleCode you define in layouts.