Working with RESTful APIs in Android: Retrofit, Volley, OkHttp

Introduction

In modern Android app development, working with RESTful APIs is a fundamental skill. RESTful APIs enable communication between your Android app and a server, allowing you to send and receive data. In this article, we’ll explore three popular libraries in the Android ecosystem for making API calls: Retrofit, Volley, and OkHttp.

Retrofit is a type-safe HTTP client for Android and Java developed by Square. It simplifies the process of making API calls by converting HTTP API endpoints into Java interfaces. With its efficient handling of data serialization and deserialization using converters, Retrofit has become a popular choice among Android developers.

Volley is a networking library provided by Google. It offers an easy-to-use and flexible API for handling network requests, image loading, and caching. Volley is particularly suitable for smaller projects or when quick and straightforward API calls are required.

OkHttp is another powerful HTTP client library from Square. It works as both a lower-level library for making API calls and as the underlying networking layer for Retrofit. OkHttp’s strong focus on performance, security, and customization makes it a versatile option for various Android projects.

Setting Up the Project

To get started, let’s set up a new Android project and integrate the libraries:

// build.gradle (app module)

dependencies {
// Add the Retrofit library
implementation ‘com.squareup.retrofit2:retrofit:2.9.0’
implementation ‘com.squareup.retrofit2:converter-gson:2.9.0’

// Add the Volley library
implementation ‘com.android.volley:volley:1.2.0’

// Add the OkHttp library
implementation ‘com.squareup.okhttp3:okhttp:4.9.1’
}

Retrofit

Retrofit is known for its simplicity and flexibility. Let’s dive into how you can use Retrofit to make API calls:

Define a data model for the API response:

public class Post {
private int id;
private String title;
private String body;
// getters and setters…
}

Create a Retrofit service interface with API endpoints:

public interface ApiService {
@GET(“posts/{id}”)
Call<Post> getPost(@Path(“id”) int postId);

@POST(“posts”)
Call<Post> createPost(@Body Post post);
}

Create a Retrofit instance and the ApiService using it:

Retrofit retrofit = new Retrofit.Builder()
.baseUrl(“https://jsonplaceholder.typicode.com/")
.addConverterFactory(GsonConverterFactory.create())
.build();

ApiService apiService = retrofit.create(ApiService.class);

Making a GET request:

Call<Post> call = apiService.getPost(1);
call.enqueue(new Callback<Post>() {
@Override
public void onResponse(Call<Post> call, Response<Post> response) {
if (response.isSuccessful() && response.body() != null) {
Post post = response.body();
// Handle the post data
}
}

@Override
public void onFailure(Call<Post> call, Throwable t) {
// Handle the failure
}
});

Making a POST request:

Post newPost = new Post(101, “New Title”, “New Body”);
Call<Post> call = apiService.createPost(newPost);
call.enqueue(new Callback<Post>() {
@Override
public void onResponse(Call<Post> call, Response<Post> response) {
if (response.isSuccessful() && response.body() != null) {
Post createdPost = response.body();
// Handle the createdPost data
}
}

@Override
public void onFailure(Call<Post> call, Throwable t) {
// Handle the failure
}
});

Volley

Volley is a versatile library for handling network requests. Here’s how you can use Volley to make API calls:

Instantiate the RequestQueue:

RequestQueue requestQueue = Volley.newRequestQueue(context);

Making a GET request:

String url = “https://jsonplaceholder.typicode.com/posts/1";
StringRequest getRequest = new StringRequest(Request.Method.GET, url,
response -> {
// Handle the response
},
error -> {
// Handle the error
});

requestQueue.add(getRequest);

Making a POST request:

String url = “https://jsonplaceholder.typicode.com/posts";
StringRequest postRequest = new StringRequest(Request.Method.POST, url,
response -> {
// Handle the response
},
error -> {
// Handle the error
}) {
@Override
protected Map<String, String> getParams() {
Map<String, String> params = new HashMap<>();
params.put(“title”, “New Title”);
params.put(“body”, “New Body”);
params.put(“userId”, “1”);
return params;
}
};

requestQueue.add(postRequest);

OkHttp

OkHttp is a robust library that can work independently or as the underlying layer for Retrofit. Here’s how you can use OkHttp for making API calls:

Create an OkHttpClient instance:

OkHttpClient client = new OkHttpClient();

Making a GET request:

String url = “https://jsonplaceholder.typicode.com/posts/1";
Request getRequest = new Request.Builder()
.url(url)
.build();

client.newCall(getRequest).enqueue(new Callback() {
@Override
public void onResponse(Call call, Response response) throws IOException {
if (response.isSuccessful() && response.body() != null) {
String responseData = response.body().string();
// Handle the response data
}
}

@Override
public void onFailure(Call call, IOException e) {
// Handle the failure
}
});

Making a POST request:

String url = “https://jsonplaceholder.typicode.com/posts";
RequestBody requestBody = new FormBody.Builder()
.add(“title”, “New Title”)
.add(“body”, “New Body”)
.add(“userId”, “1”)
.build();

Request postRequest = new Request.Builder()
.url(url)
.post(requestBody)
.build();

client.newCall(postRequest).enqueue(new Callback() {
@Override
public void onResponse(Call call, Response response) throws IOException {
if (response.isSuccessful() && response.body() != null) {
String responseData = response.body().string();
// Handle the response data
}
}

@Override
public void onFailure(Call call, IOException e) {
// Handle the failure
}
});

Comparing the Libraries

Each library has its strengths and fits different project requirements. Retrofit’s simplicity and elegant API design make it a top choice for many projects, especially when combined with Gson for JSON parsing. Volley is great for smaller projects or when quick setup and image loading are needed. OkHttp’s flexibility and performance-oriented features are ideal for projects with specific networking requirements.

Best Practices

Regardless of the library you choose, consider the following best practices when working with RESTful APIs in Android:

• Use background threads or coroutines for network calls to avoid blocking the UI thread.
• Implement caching and handle network errors gracefully to provide a smooth user experience.
• Secure sensitive data by using HTTPS and authenticating your API calls if required.
• Consider using libraries for JSON parsing, such as Gson or Moshi, to convert JSON responses to Java objects.
• Monitor and optimize network calls using tools like Stetho or Chuck.

Conclusion

In this article, we explored how to work with RESTful APIs in Android using three popular libraries: Retrofit, Volley, and OkHttp. Each library has its unique features and advantages, making them suitable for different scenarios. By integrating these libraries into your Android projects, you can efficiently communicate with servers and provide a seamless user experience in your apps.

Remember to choose the library that best aligns with your project’s requirements and development preferences.