20 Android Retrofit Interview Questions and Answers

Retrofit is a popular networking library for Android development. If you’re applying for an Android developer position, it’s likely that you’ll be asked questions about Retrofit 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 the most common Retrofit questions and how you should answer them.

Android Retrofit Interview Questions and Answers

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

1. What is Retrofit?

Retrofit is a type-safe HTTP client for Android and Java.

2. Can you explain how to use Retrofit in an Android application?

Retrofit is a library that can be used on Android to simplify the process of making network requests. It can be used to make requests to RESTful web services, and can also be used to make requests to other types of web services. To use Retrofit in an Android application, you first need to add the library to your project. Then, you need to create an interface that defines the methods that you want to use to make requests. Finally, you need to create a Retrofit instance and use it to make requests.

3. How do you set up a new project with Retrofit in it?

The first step is to add the Retrofit library to your project dependencies. Then, you need to create an interface that defines the endpoints you want to call. Finally, you need to create a Retrofit instance and use it to generate an implementation of your interface.

4. What are the main components of a REST API call?

The main components of a REST API call are the URL, the HTTP method, the headers, and the body. The URL is the address of the server that you are trying to access. The HTTP method is the type of request that you are making to the server, such as GET, POST, PUT, or DELETE. The headers are the additional information that you are sending along with the request. The body is the data that you are sending to the server.

5. Can you give me some examples of real-world applications that make extensive use of Retrofit?

Some examples of real-world applications that use Retrofit extensively are the Android applications for Netflix, Airbnb, and Yelp. All of these apps need to communicate with a backend server in order to function, and Retrofit makes it easy to set up this communication.

6. Why should we use Retrofit over other libraries like Volley or OkHttp?

Retrofit is a great library for making network requests on Android because it is easy to use and has a lot of features. With Retrofit, you can easily add query parameters, add headers, and specify the request body all in one place. Retrofit also makes it easy to parse JSON responses and supports both synchronous and asynchronous requests.

7. Is it possible to customize JSON parsing using Retrofit? If yes, then how?

Yes, it is possible to customize JSON parsing using Retrofit. This can be done by creating a custom converter that extends the Converter.Factory class. This custom converter can then be used to parse the JSON response into the desired format.

8. What’s the best way to send an image using Retrofit?

The best way to send an image using Retrofit is to first encode the image into a Base64 string, and then send that string as a parameter in the Retrofit request.

9. When would you consider using Volley instead of Retrofit?

Volley is a good choice if you need a light-weight solution or if you need to support older versions of Android. Retrofit is a good choice if you’re looking for a more feature-rich library.

10. Does Retrofit support caching? If so, how does it work?

Yes, Retrofit supports caching. When you make a request, Retrofit will first check if there is a cached response for that request. If there is, it will return the cached response. If there is no cached response, Retrofit will make the network request and cache the response for future requests.

11. What do you understand about GSON annotations?

GSON annotations are used to specify how a field should be serialized or deserialized by the GSON library. For example, the @SerializedName annotation can be used to specify the name of a field in the JSON representation, while the @Expose annotation can be used to specify which fields should be included in the JSON representation.

12. Can you explain what annotations are used for and which ones you have experience working with?

Annotations are a way of adding metadata to Java code. They can be used for a variety of purposes, such as specifying that a certain method should be called when a button is clicked, or that a certain class should be serialized to JSON. I have experience working with a few different annotations, including @Override, @Nullable, and @JsonProperty.

13. What is the difference between @Path and @Query parameters?

@Path parameters are used to fill in the dynamic values in a URL path, while @Query parameters are used to specify values for query string parameters.

14. Do you think Retrofit can be used from both Kotlin and Java simultaneously in the same project?

Yes, I think that Retrofit can be used from both Kotlin and Java simultaneously in the same project. I don’t see any reason why it couldn’t be used in this way, as it would just be a matter of adding the appropriate dependencies for each language.

15. What is the purpose of Callback methods in Retrofit?

The purpose of the Callback methods is to notify the caller of the Retrofit request whether the request was successful or not. If the request was successful, then the onResponse() method is called. If the request was not successful, then the onFailure() method is called.

16. What is meant by synchronous and asynchronous calls in Retrofit?

A synchronous Retrofit call will execute the network request on the same thread that the Retrofit call was made on. This means that the main UI thread will be blocked while the network request is being executed. An asynchronous Retrofit call will instead create a new thread to execute the network request on, meaning that the main UI thread will not be blocked.

17. What is the difference between POST and GET requests?

The main difference between POST and GET requests is that POST requests include a body payload that can be used to send data to the server, while GET requests do not. This means that POST requests are typically used when you want to create or update data on the server, while GET requests are used for fetching data from the server.

18. How can multiple headers be sent along with a request in Retrofit?

In Retrofit, you can specify multiple headers by creating a Headers class and adding multiple @Header annotations to it.

19. What is your understanding of interceptors in Retrofit?

Interceptors are a powerful mechanism that can monitor, rewrite, and retry network requests. In Retrofit, interceptors are used to intercept and modify HTTP requests before they are sent to the server. This can be useful for adding common headers, query parameters, or for logging network requests.

20. What is the significance of retrofit logging level?

The logging level is used to determine the amount of information that is logged by the Retrofit library. By default, Retrofit will only log requests and responses at the “basic” level, which includes information such as the request method, URL, headers, and body. However, you can increase the logging level to “headers” or “full”, which will include additional information such as the request and response headers and bodies.