what is mvvm in android

what is mvvm in android

MVVM stands for Model, View, ViewModel. Model: This holds the data of the application. It cannot directly talk to the View. Generally, it's recommended to expose the data to the ViewModel through Observables. View: It represents the UI of the application devoid of any Application Logic.

Why MVVM is used in Android?

In Android, MVC refers to the default pattern where an Activity acts as a controller and XML files are views. MVVM treats both Activity classes and XML files as views, and ViewModel classes are where you write your business logic. It completely separates an app's UI from its logic.

a.Model: It represents the data and the business logic of the Android Application. It consists of the business logic - local and remote data source, model classes, and repository.

b.View: It consists of the UI Code(Activity, Fragment), XML. It sends the user action to the ViewModel but does not get the response back directly. To get the response, it has to subscribe to the observables which ViewModel exposes to it.

c.ViewModel: It is a bridge between the View and Model(business logic). It does not have any clue which View has to use it as it does not have a direct reference to the View. So basically, the ViewModel should not be aware of the view who is interacting with. It interacts with the Model and exposes the observable that can be observed by the View.