20 MVVM Android Interview Questions and Answers

MVVM is a popular design pattern used in Android development. If you’re applying for a position that involves Android development, it’s likely that you’ll be asked questions about MVVM during your interview. Knowing how to answer these questions can help you impress the hiring manager and improve your chances of getting the job. In this article, we discuss some of the most common MVVM Android interview questions and provide tips on how to answer them.

MVVM Android Interview Questions and Answers

Here are 20 commonly asked MVVM Android interview questions and answers to prepare you for your interview:

1. What is MVVM?

MVVM is a software design pattern that is used for developing user interfaces. It is derived from MVC, but it uses a different approach to separating the concerns of the application. In MVVM, the ViewModel is responsible for handling the data and the business logic, while the View is responsible for displaying the data. This separation of concerns makes it easier to develop and maintain complex user interfaces.

2. Why do you think MVVM is a better choice than MVC for developing Android apps?

I think that MVVM is a better choice for developing Android apps for a few reasons. First, it allows for a more separation of concerns between the different parts of the app, which can make development and maintenance simpler. Second, it can make it easier to bind data to the UI, since the ViewModel can act as a mediator between the data and the View. Finally, it can help to improve performance, since the ViewModel can handle tasks that would otherwise need to be done on the UI thread.

3. Is it necessary to use the data binding library with MVVM on Android?

While the data binding library is not required to use MVVM on Android, it can greatly simplify the process. The data binding library allows you to bind data directly to views, eliminating the need for manual view updates. This can help to keep your code clean and maintainable.

4. Can you explain how data binding works in MVVM?

Data binding is a process that allows you to automatically synchronize your ViewModel and View. When data binding is enabled, any changes that you make to your ViewModel will be automatically reflected in your View. This makes it easier to keep your View and ViewModel in sync, and can help to reduce the amount of boilerplate code that you need to write.

5. How does Model-View-ViewModel (MVVM) differ from other design patterns like Model-View-Controller (MVC)?

The main difference between MVVM and other design patterns is that MVVM separates the view (i.e. the user interface) from the model (i.e. the data). This separation allows for a more modular and testable codebase. Additionally, MVVM typically uses data binding to automatically update the view when the model changes, which further reduces the amount of code that needs to be written.

6. What’s the difference between two-way and one-way data binding?

Two-way data binding means that changes to either the model or the view will update the other automatically. One-way data binding means that changes to the model will update the view, but not vice versa.

7. What are some of the advantages and disadvantages of using MVVM in Android development?

Some advantages of using MVVM in Android development include the ability to easily bind data to UI elements, a clean separation of concerns between the View and ViewModel, and the ability to easily unit test the ViewModel. Some disadvantages of using MVVM in Android development include the potential for a lot of boilerplate code, and the fact that it can be difficult to debug data bindings.

8. Are there any alternate ways to achieve MVVM architecture outside of the official data binding library? If yes, can you give me an example?

There are a few ways to achieve MVVM architecture outside of the official data binding library. One way is to use the LiveData and ViewModel classes from the Android Architecture Components library. Another way is to use the RxJava library to create observables that can be subscribed to by the UI.

9. How can you improve performance when using data binding in Android?

One way to improve performance when using data binding is to use the @Bindable annotation. This annotation tells the data binding system to only update the UI when the data has actually changed. Without this annotation, the data binding system will update the UI every time any data is changed, even if the UI doesn’t need to be updated.

10. How would you implement MVVM without using the support libraries?

There are a few ways to implement MVVM without using the support libraries. One way would be to use a library like RxJava to manage your data bindings. Another way would be to use the Data Binding Library from Google.

11. What is LiveData? Why should we use it in our android app?

LiveData is a data holder class that can be observed within a given lifecycle. This means that you can observe LiveData objects for changes and update the UI accordingly. LiveData is especially useful in Android applications because it helps to avoid memory leaks and can automatically update the UI when data changes.

12. What’s the difference between Observables and LiveData?

LiveData is an observable data holder class. It is lifecycle-aware, meaning it respects the lifecycle of other app components, such as activities, fragments, or services. This awareness ensures LiveData only updates app component observers that are in an active lifecycle state.

Observables, on the other hand, are not lifecycle-aware. This means they will continue to emit data even if the observer is no longer in an active state, such as when an activity has been destroyed. This can lead to memory leaks if the observer is not unregistered when no longer needed.

13. What is the recommended way of implementing a ViewModel class in an Android app?

The recommended way of implementing a ViewModel class in an Android app is to use the Android Architecture Components library. This library provides a ViewModel class that is specifically designed for use with Android apps. The ViewModel class is designed to help manage data that is specific to a particular activity or fragment, and it is also designed to survive configuration changes such as screen rotations.

14. Can you explain what dependency injection means in context of MVVM?

Dependency injection is a technique used to remove the hard-coded dependencies from a class, making it more flexible and easier to test. In the context of MVVM, dependency injection can be used to inject view models into views, allowing the view model and view to be decoupled. This makes it easier to unit test the view model, as it can be tested in isolation.

15. Does MVVM depend on some other architectural pattern or framework?

No, MVVM does not depend on any other architectural pattern or framework.

16. What tools and technologies are used for implementing MVVM on Android?

There are a few different ways to implement MVVM on Android. One popular way is to use the Android Data Binding Library, which allows you to bind data directly to views in your layout file. Other popular tools and technologies used for MVVM on Android include RxJava and LiveData.

17. Can you explain what reactive programming is?

Reactive programming is a programming paradigm that is concerned with data streams and the propagation of change. This means that when a piece of data changes, all observers of that data are notified and updated automatically. This is in contrast to the more traditional approach of having to manually keep track of what data has changed and then update the observers accordingly.

18. How does reactive programming relate to event handling?

Reactive programming is a programming paradigm that is concerned with data streams and the propagation of changes. Event handling, on the other hand, is a way of responding to events that occur in a program. In the context of Android development, reactive programming can be used to handle events such as user input, while event handling is used to respond to events such as button clicks.

19. What do you understand about observables and observers in the context of reactive programming?

In reactive programming, observables are objects that emit a stream of data, and observers are objects that consume that data. In the context of Android development, observables can be used to emit data from a ViewModel to a View, and observers can be used to consume that data and update the UI.

20. Do you think RxJava is useful for Java developers who want to learn more about reactive programming?

Yes, I think RxJava is a great tool for Java developers who want to learn more about reactive programming. It can be used to create asynchronous and event-based applications.