Languages

Understanding Okhttp3 and Retrofit in Android

When designing an Android application, it is vital to understand how to send and manage network requests. Determining the frameworks to use is also critical.  Network calls are frequently used to retrieve or change API data/media from a server. This is a typical task in Android development, especially for clients who use dynamic data.

Understanding Okio's okhttp3 and retrofit

Okio-okhttp3 is a library that works in conjunction with java.io and java.nio to make data access, storage, and processing considerably easier. It started as a component of OkHttp.

Retrofit is a type-safe REST client for Java and Android application development. It consists of interfaces, classes, and methods that provide the required functionalities.

JSON or XML data may be parsed and converted to POJOs (Plain Old Java Objects) using the Retrofit library.

Okio is a simple and fast Android networking library suitable for complex challenges.

Prerequisites

To follow along with this article, you need to:

Have a basic understanding of Android programming
Understand the basics of the Kotlin programming language
Have basic knowledge of view binding

Goals

This article primarily compares Okio's okhttp3 library and Retrofit in terms of conducting network calls.

It also highlights the benefits and drawbacks of both libraries, which library is the best to use, and how both are implemented in Android.

Advantages of Okio's okhttp3 library

It is based on byte string and buffers, which compact a lot of functionality into a simple API. This saves both the processing power and memory.
Okio features stream types called bufferSource and buffersink - which operate as inputStream and outputStream respectively.
It is simple to construct, use, and test using the two streams.

Disadvantages of Okio's okhttp3 library

Processing data may be slow because there is no direct communication with the webserver when making network calls.
Request cancellation is not supported by the Okio library.
It cannot handle both synchronous and asynchronous network requests at the same time.

Advantages of Retrofit library

In comparison to other network libraries, it is extremely fast.
It has direct access to the web service and can communicate with it.
It is simple to use and understand.
It has the option to make a cancellation request.
It can handle both post requests and multipart uploads.

Disadvantages of Retrofit library

Retrofit is not able to load images. Other libraries, such as Glide and Picasso, are required.
Retrofit does not support prioritization.

Which library is the best to use

When comparing the performance of okio's okhttp3 and retrofit in performing network calls, Retrofit would be considered the best.

This is because retrofit is fast, can communicate directly with the server. This means that no intermediate code is required to convert data from the server to a form that can be understood.

It also supports request cancellation, which is not available in okio's okhttp3.

Let's get coding!

Step 1 - Create a new project

To make a new project, go to File > New, then New Project, and select Empty activity.

Give the project a descriptive name and select Kotlin as the preferred programming language.

New project

Step 2 - Adding necessary dependencies

Okio's okhttp3 dependency

Include these dependencies to your app-level build.gradle file to set up the project:

// Okio/Okhttp3 library
implementation 'com.squareup.okhttp3:okhttp:4.9.1'

Retrofit dependency

// Retrofit
implementation 'com.squareup.retrofit2:retrofit:2.9.0'
implementation 'com.squareup.retrofit2:converter-gson:2.9.0'

Step 3 - Creating the user interface

Setting up the region where network data is displayed is crucial. In this example, we'll use a Textview to hold the required data and two buttons.

One button will fetch the data using retrofit while the other will use okio's okhttp library.

Below is how the user interface is implemented:

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/textViewok"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginEnd="16dp"
        android:textSize="24sp"
        android:text="Text to be fetched from internet"
        android:textAlignment="center"
        android:textStyle="bold"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/btnRetrofit"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginTop="32dp"
        android:layout_marginEnd="8dp"
        android:text="Load with retrofit"
        android:textAllCaps="false"
        app:layout_constraintEnd_toStartOf="@+id/btnOkhttp3"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textViewok" />

    <Button
        android:id="@+id/btnOkhttp3"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginEnd="8dp"
        android:text="Load with okhttp3"
        android:textAllCaps="false"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toEndOf="@+id/btnRetrofit"
        app:layout_constraintTop_toTopOf="@+id/btnRetrofit" />
</androidx.constraintlayout.widget.ConstraintLayout>

user interface

Ensure you add the internet permissions in the manifest, otherwise, the application will crash.

Step 4 - Setting up the project

Retrofit

To provide certain services, we'll require the following classes to set up retrofit:

Model

The Model class is used to illustrate the data format and how it can be transferred to the current user interface. For this case, the model class is as shown below:

data class Dog(
    Val message: String?,
    Val status: String?
)

Constants

This class only contains constant values that will not change throughout the program, it is implemented as shown below:

object Constants {
    const Val BASE_URL = "https://dog.ceo/api/breeds/"
}

ApiService

Api service is a method-based interface that calls data based on the endpoint of the URL provided. The API service used is as shown below:

interface ApiService {
    @GET("image/random")
    fun getRandomDog() : Call<Dog>
}

Retrofit Class

This is a class that uses Retrofit to make network calls based on the data from the predefined API service.

The base url and the converter factory, which translates the data appropriately, are required for Retrofit.

This is an object class, as indicated below:

object DogApi {
    private val retrofit = Retrofit.Builder()
        .baseUrl(BASE_URL)
        .addConverterFactory(GsonConverterFactory.create())
        .build()

    val apiService by lazy {
        retrofit.create(ApiService::class.java)
    }

}

Okhttp3

To use this library to make network calls, first, create an instance of OkhttpClient(), then declare and initialize a url variable with the url to be used.

Finally, create an instance of Request builder() to set the provided url:

 val client = OkHttpClient()
        val url = "https://dog.ceo/api/breeds/image/random"
        val request = Request.Builder()
            .url(url)
            .build()

Step 5 - Performing network calls

Retrofit

Add an on-click listener to the button then access the API service and retrieve the method within the API service using the Retrofit object class.

The callback is alerted of its response or even if an error occurred by communicating to the server using the enqueue method.

Data is assigned to the Textview when there is a response. However, when there is an error, a message is logged:

 binding.btnRetrofit.setOnClickListener {
           DogApi.apiService.getRandomDog().enqueue(object: Callback<Dog> {
               override fun onResponse(call: Call<Dog>, response: Response<Dog>) {
                   binding.textViewok.text = response.body().toString()
               }

               override fun onFailure(call: Call<Dog>, t: Throwable) {
                   Log.d(TAG, "onFailure: ${t.message}")
               }

           })
       }

Okio's Okhttp3

Add an onClickListener() to btnOkhttp3, using the client instance that we have already created in the previous step.

Next, access the newcall() method that would require a request to be passed. Use the enqueue method to obtain callback responses or errors.

onResponse() checks whether the response is successful. If it is successful, it converts the response to a readable form.

Okio's okhttp3 would need the data to be set to a Textview, but this happens within a uiThread. OnError() logs the error message:

binding.btnOkhttp3.setOnClickListener {

            client.newCall(request).enqueue(object: okhttp3.Callback{
                override fun onFailure(call: okhttp3.Call, e: IOException) {
                    Log.d(TAG, "onFailure: ${e.message}")
                }

                override fun onResponse(call: okhttp3.Call, response: okhttp3.Response) {
                    if (response.isSuccessful){
                        //converts data to a readable form
                        val jsonData: ResponseBody? = response.body
                        val result = JSONObject(jsonData?.string())

                        //setting data to the ui thread
                        runOnUiThread {
                            binding.textViewok.text = result.toString()
                        }
                    }
                }

            })
        }