Android Development Masterclass/

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Using Retrofit for REST API Calls

Using Retrofit for REST API Calls

Learn how to make REST API calls using a networking library called Retrofit.

We'll cover the following...

Introduction

Retrofit is a networking library developed by Square that lets us make REST API calls. The library simplifies downloading JSON and XML responses from the APIs. It also simplifies interacting with both authenticated and unauthenticated API calls.

This lesson will teach us how to make network calls to fetch data from servers and consume that data in our Android applications.

Prerequisites

Before we get started with Retrofit, make sure that the internet permissions are granted to the application in the AndroidManifest.xml file.

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<manifest xmlns:android="http://schemas.android.com/apk/res/android">
    <uses-permission android:name="android.permission.INTERNET" />
</manifest>

We’ll use an open-source countries API. The API has an /all endpoint that returns a list of all countries. Keep the API URL handy since we’ll use it later in this lesson.

Adding library dependencies

Let’s add the dependencies for the Retrofit library in the app-level Gradle file.

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implementation 'com.google.code.gson:gson:2.8.7'
implementation 'com.squareup.retrofit2:retrofit:2.9.0'
implementation 'com.squareup.retrofit2:converter-gson:2.9.0'

Defining the data class

We’ll take the example of the country list API to demonstrate the usage of the GET API call using the Retrofit library. The response of the API contains a list of countries with ...