Liferay Screens for Android is composed of a Core, a Screenlet layer, a View layer, Interactors, and Server Connectors. Interactors are technically part of the core, but are worth covering separately. They facilitate interaction with both local and remote data sources, as well as communication between the Screenlet layer and the Liferay Mobile SDK.
Each component is described below.
Core: includes all the base classes for developing other Screens components. It’s a micro-framework that lets developers write their own Screenlets, Views, and Interactors.
Screenlets: Java view classes for inserting into any activity or fragment view hierarchy. They render a selected layout in the runtime and in Android Studio’s visual editor and react to UI events, sending any necessary server requests. You can set a Screenlet’s properties from its layout XML file and Java classes. The Screenlets bundled with Liferay Screens are known collectively as the Screenlet Library.
Server Connectors: a collection of classes that interact with different Liferay DXP versions. These classes abstract away the complexity of communicating with different versions. This allows the developer to call API methods and the correct Interactor without worrying about the specific Liferay DXP version.
Interactors: implement specific use cases for communicating with servers. They can use local and remote data sources. Most Interactors use the Liferay Mobile SDK to exchange data with a Liferay instance. If a user action or use case needs to execute more than one query on a local or remote store, the sequence is done in the corresponding Interactor. If a Screenlet supports more than one user action or use case, an Interactor must be created for each. Interactors are typically bound to one specific Liferay version, and instantiated by a Server Connector. Interactors run in a background thread and can therefore perform intensive operations without blocking the UI thread.
Views: a set of layouts and accompanying custom view classes that present Screenlets to the user.
Next, the core layer is described in detail.