Retrofit is a type-safe http client which is used to retrieve, update and delete thedata from web services.
Nowadays retrofit library is popular among the developers to use the API key.
The Kotlin team defines coroutines as “lightweight threads”.
Kotlin coroutines introduce a new style of concurrency that can be used on Android to simplify async code.
In this article, we will learn about retrofit using Kotlin coroutine.
So we will be using Retrofit for network requests.
Retrofit is a very popular library used for working APIs and very commonly used as well.
We will learn it by making a simple app using an API to get some data using Retrofit.
Step 1: Create a New Project
Step 2: Add dependency
Navigate to the Gradle Scripts > build.gradle(Module:app) and add the below dependency in the dependencies section.
// retrofit
implementation ‘com.squareup.retrofit2:retrofit:2.9.0’
// GSON
implementation ‘com.squareup.retrofit2:converter-gson:2.9.0’
// coroutine
implementation ‘org.jetbrains.kotlinx:kotlinx-coroutines-an..’
implementation ‘org.jetbrains.kotlinx:kotlinx-coroutines-co..’
We are using GSON to convert JSON to kotlin(Java) object.
We will add these dependencies in build.gradle file inside our project.
Step 3: We will use the below API
https://quotable.io/quotes?page=1.json
Step 4: Then we will create data classes according to JSON response
In JSON response we have 2 JSON objects, So we will create 2 data class
QuoteList
Results
data class QuoteList(
val count: Int,
val lastItemIndex: Int,
val page: Int,
val results: List<Result>,
val totalCount: Int,
val totalPages: Int
)
data class Result(
val \_id: String,
val author: String,
val authorSlug: String,
val content: String,
val dateAdded: String,
val dateModified: String,
val length: Int,
val tags: List<String>
)
Step 5: We will create a Retrofit interface
to add the endpoints of the URL
(quotes in our case is the endpoint)
interface QuotesApi {
@GET("/quotes")
suspend fun getQuotes() : Response<QuoteList>
}
Step 6: We will create a new file to get the Retrofit object
In this file, we will have a function that will return the Retrofit object.
object RetrofitHelper {
`val baseUrl = "`[https://quotable.io/](https://quotable.io/)`"`
`fun getInstance(): Retrofit {`
`return` `Retrofit.Builder().baseUrl(baseUrl)`
`.addConverterFactory(GsonConverterFactory.create())`
`// we need to add converter factory to`
`// convert JSON object to Java object`
`.build()`
`}`
}
Step 7: Now we will link the Retrofit object and Retrofit interface file in MainActivity
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity\_main)
**val quotesApi = RetrofitHelper.getInstance().create(QuotesApi::**[**class.java**](http://class.java)**)**
**// launching a new coroutine**
**GlobalScope.launch {**
**val result = quotesApi.getQuotes()**
**if (result != null)**
**// Checking the results**
**Log.d("ayush: ", result.body().toString())**
**}**
}
}
Step 8: Add Internet permission in the manifests file
<uses-permission android:name=”android.permission.INTERNET”></uses-permission>
Results: we can check the logcat window. We can see the result in the green box.