In Android architecture, a ViewModel acts as a bridge between the user interface and the underlying data sources, facilitating the management and presentation of UI-related data in a lifecycle-aware manner. Introduced as part of the Android Architecture Components, ViewModel is designed to store and manage UI-related data in a way that survives configuration changes (such as screen rotations) and persists across the lifecycle of an activity or fragment.
The primary purpose of a ViewModel is to separate the concerns of data management from the UI logic, promoting a more modular and maintainable codebase. By encapsulating UI-related data and business logic within a ViewModel, developers can create more testable, scalable, and maintainable applications.
ViewModels are designed to be lifecycle-aware, meaning they are tied to the lifecycle of the associated activity or fragment. When an activity or fragment is destroyed and recreated due to configuration changes, such as orientation changes, the ViewModel survives and retains its state, ensuring that UI-related data remains intact and consistent across different lifecycle states.
ViewModels are typically used to encapsulate and manage data that is required to be retained across configuration changes, such as UI state, user input, and view data. They can also be used to perform asynchronous data loading operations, manage UI navigation, and coordinate interactions between different components of an application.
ViewModels are instantiated using the ViewModelProvider class, which is responsible for creating and managing ViewModel instances associated with specific lifecycle scopes, such as activities or fragments. ViewModels should be accessed and observed from within the UI components (activities or fragments) they are associated with, using LiveData or other observable mechanisms to observe changes in the ViewModel’s data and update the UI accordingly.
