Difference Between MVP and MVVM Architecture Pattern in Android

Both MVP (Model-View-Presenter) and MVVM (Model-View-ViewModel) are design patterns intended to separate concerns in applications, particularly with regards to the separation between the user interface and underlying logic. In Android, these patterns have gained traction as they make the codebase more modular, testable, and maintainable. Here's a detailed comparison:

MVP (Model-View-Presenter):

Model: Represents the data source and business logic. It's responsible for fetching, storing, and processing data.
View: Represents the UI of the application. In Android, this could be an Activity, Fragment, or custom View. The View is passive and is responsible for forwarding user interactions to the Presenter.
Presenter: Acts as a mediator between the Model and View. It's responsible for handling all UI logic. The Presenter retrieves data from the Model, processes it, and updates the View accordingly.
In Android:
- The View (usually an Activity or Fragment) has a reference to the Presenter.
- The Presenter is devoid of any Android framework code, which makes it more testable.
- The Model encapsulates data access and business logic.

MVVM (Model-View-ViewModel):

Model: As in MVP, represents the data source and business logic.
View: Displays the data and is passive. It's not supposed to contain any logic.
ViewModel: It's a bridge between the Model and the View. The ViewModel holds the presentation logic and is responsible for transforming data from the Model into a format that can be easily displayed by the View. It doesn't have a direct reference to the View. Instead, it exposes observable data that the View can bind to.
In Android:
- The View (Activity or Fragment) binds to observables exposed by the ViewModel.
- The ViewModel uses LiveData or other observables, making it lifecycle-aware. This means it can manage data in a way that respects the Android component lifecycle (e.g., surviving configuration changes).
- The Model remains as the data provider and business logic handler.

Key Differences:

Binding:
- MVP: The View has a direct reference to the Presenter, but not vice versa. The Presenter updates the View explicitly.
- MVVM: Data-binding is often used to bind the View to the ViewModel, making manual updates unnecessary. When data in the ViewModel changes, the View automatically reflects these changes.
Decoupling:
- MVP: Although there's a clear distinction between View and Presenter, there's still a direct link between them.
- MVVM: The View and ViewModel are more decoupled because they communicate through data-binding and observables, rather than direct method calls.
Testability:
- MVP: Easier to test than traditional MVC in Android because the Presenter is decoupled from the Android framework.
- MVVM: The ViewModel is also easy to test as it doesn't have a direct reference to the View and doesn't depend on the Android framework.
Lifecycle Management:
- MVP: The Presenter needs to handle lifecycle events of the View, such as dealing with rotation or other configuration changes.
- MVVM: With tools like LiveData, the ViewModel becomes lifecycle-aware, reducing the boilerplate code to handle Android lifecycle events.

In conclusion, both MVP and MVVM aim for a cleaner separation of concerns than traditional MVC. The choice between MVP and MVVM often boils down to specific project needs, team familiarity, and the desired level of decoupling. In recent years, MVVM has gained more popularity in Android, especially with the introduction of the Android Jetpack libraries that support this architecture natively.