MVVM pattern in Android Kotlin - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does MVVM stand for in Android development?

MVVM stands for Model-View-ViewModel. It is a design pattern that helps separate the user interface (View) from the business logic (Model) using a ViewModel as a bridge.

beginner

What is the role of the ViewModel in MVVM?

The ViewModel holds and manages UI-related data. It communicates with the Model to get data and prepares it for the View. It survives configuration changes like screen rotations.

intermediate

How does the View observe data changes in MVVM?

The View observes LiveData or StateFlow objects exposed by the ViewModel. When data changes, the View automatically updates without manual intervention.

intermediate

Why is MVVM better than putting all code in the Activity or Fragment?

MVVM separates concerns, making code easier to read, test, and maintain. It prevents Activities or Fragments from becoming too large and handles lifecycle changes better.

intermediate

In MVVM, where should network or database operations be performed?

Network or database operations should be done in the Model or Repository layer. The ViewModel requests data from the Model and exposes it to the View.

In MVVM, which component directly updates the UI?

A ViewModel

B Model

C View

D Repository

The View is responsible for displaying the UI and updating it based on data changes.

Which Android class is commonly used in ViewModel to hold observable data?

A Service

B Intent

C Bundle

D LiveData

LiveData is an observable data holder class that the View can observe for changes.

What is a key benefit of using ViewModel in MVVM?

A It survives configuration changes

B It handles UI rendering

C It stores user preferences

D It manages network connections

ViewModel survives configuration changes like screen rotations, preserving UI data.

Where should business logic be placed in MVVM?

A Model

B ViewModel

C Activity

D View

Business logic belongs in the Model layer, keeping ViewModel focused on UI data preparation.

Which of these is NOT a responsibility of the ViewModel?

A Fetching data from Model

B Handling user input events directly

C Exposing data to View

D Surviving configuration changes

User input events are usually handled by the View, which then informs the ViewModel.

Explain the roles of Model, View, and ViewModel in the MVVM pattern.

Think about who does what in the app: data, UI, and the middleman.

Describe how MVVM helps manage screen rotations in Android apps.

Consider what happens when the screen turns and the Activity restarts.