Kotlin Call Retrofit2 Service Using OKHTTP3 Method(Get) Example

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In this example, I will show you how to call Retrofit2 service using okhttp3 and display download data into RecyclerView.

Kotlin Call Retrofit2 Service Using okhttp3 Example Video

  • You can also go through this video explanation.

Kotlin Call Retrofit2 Service Using OKHTTP3 Method(Get) Example

Creating a New Project

  • So first create a new Android Studio project using Kotlin.
  • Once the project is loaded come inside the activity_main.xml and remove the Hello World TextView.
Android studio project screen

JSON Service Url:
https://jsonplaceholder.typicode.com/posts/1/comments

JSON service output screen:-

Step 1:
Open build.gradle and add following dependency and rebuild the project.
implementation 'com.google.code.gson:gson:2.8.4'
implementation 'com.squareup.okhttp3:logging-interceptor:3.8.0'
implementation 'com.squareup.retrofit2:retrofit:2.3.0'
implementation 'com.squareup.retrofit2:converter-gson:2.3.0'
implementation 'com.google.android.material:material:1.2.0'
implementation 'androidx.recyclerview:recyclerview:1.1.0'
implementation 'androidx.cardview:cardview:1.0.0'
Step 2:
Open AndroidManifest.xml and add Internet Permission.
<uses-permission android:name="android.permission.INTERNET"/>
Step 3:
Create new Package:- model
CommentsDataModel.kt
Create new class CommentsDataModel.kt under model package and Add following code.
package com.kotlinkatta.retrofitget.model

import com.google.gson.annotations.Expose
import com.google.gson.annotations.SerializedName

data class CommentsDataModel(
    @Expose
    @SerializedName("postId")
    val postId: Integer,
    @Expose
    @SerializedName("id")
    val id: Integer,
    @Expose
    @SerializedName("name")
    val name: String,
    @Expose
    @SerializedName("email")
    val email: String,
    @Expose
    @SerializedName("body")
    val body: String
)
Step 4:
Create new Layout:- comments_data_row.xml
Create new comments_data_row.xml file under layout folder and Add following code.
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="wrap_content">

<androidx.cardview.widget.CardView
    android:layout_margin="10dp"
    app:cardCornerRadius="5dp"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@color/colorAccent">

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_margin="3dp"
            android:padding="10dp"
            android:background="#ffffff"
            android:orientation="vertical">

            <TextView
                android:id="@+id/txt_name"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:textColor="#000000"
                android:justificationMode="inter_word"
                android:textSize="20dp" />

            <TextView
                android:layout_marginTop="3dp"
                android:id="@+id/txt_email"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:textColor="#000000"
                android:justificationMode="inter_word"
                android:textSize="17dp" />

            <TextView
                android:layout_marginTop="3dp"
                android:id="@+id/txt_body"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:justificationMode="inter_word"
                android:textSize="17dp" />
        </LinearLayout>
    </LinearLayout>
</androidx.cardview.widget.CardView>
</LinearLayout>
Step 5:
Create new Package:- adapter
CommentsDataAdapter.kt
Create new class CommentsDataAdapter.kt under adapter package and Add following code.
package com.kotlinkatta.retrofitget.adapter

import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.recyclerview.widget.RecyclerView
import com.kotlinkatta.retrofitget.model.CommentsDataModel
import com.kotlinkatta.retrofitokhttp.R
import kotlinx.android.synthetic.main.comments_data_row.view.*

class CommentsDataAdapter(val userList: List<CommentsDataModel>) : RecyclerView.Adapter<CommentsDataAdapter.ViewHolder>() {

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
        val v = LayoutInflater.from(parent.context).inflate(R.layout.comments_data_row, parent, false)
        return ViewHolder(v)
    }

    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
        val commentsDataModel : CommentsDataModel = userList[position]
        holder.txt_name.text = "Name : " + commentsDataModel.name
        holder.txt_email.text = "Email : " + commentsDataModel.email
        holder.txt_body.text = "Body : " + commentsDataModel.body
    }

    override fun getItemCount(): Int {
        return userList.size
    }

    class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
        val txt_name = itemView.txt_name
        val txt_email = itemView.txt_email
        val txt_body = itemView.txt_body
    }
}
Step 6:
Create new Package:- retofitdata
DataService.kt
Create new class DataService.kt under retofitdata package and Add following code.
package com.kotlinkatta.retrofitget.retofitdata

import com.kotlinkatta.retrofitget.model.CommentsDataModel
import retrofit2.Call
import retrofit2.http.GET

interface DataService {
    @GET("/posts/1/comments")
    fun getAllComments(): Call<List<CommentsDataModel>>
}
Step 7:
RetrofitClient.kt
Create new class RetrofitClient.kt under retofitdata package and Add following code.
package com.kotlinkatta.retrofitget.retofitdata

import com.google.gson.GsonBuilder
import okhttp3.OkHttpClient
import okhttp3.logging.HttpLoggingInterceptor
import retrofit2.Retrofit
import retrofit2.converter.gson.GsonConverterFactory

object RetrofitClient {
    var BASE_URL:String="https://jsonplaceholder.typicode.com"
    val getClient: DataService
        get() {
            val gson = GsonBuilder().setLenient().create()
            val interceptor = HttpLoggingInterceptor()
            interceptor.setLevel(HttpLoggingInterceptor.Level.BODY)
            val client = OkHttpClient.Builder().addInterceptor(interceptor).build()

            val retrofit = Retrofit.Builder()
                .baseUrl(BASE_URL)
                .client(client)
                .addConverterFactory(GsonConverterFactory.create(gson))
                .build()

            return retrofit.create(DataService::class.java)
        }
}
Step 8:
MainActivity.kt
Add following code into MainActivity.kt.
package com.kotlinkatta.retrofitokhttp

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.view.View
import android.widget.ProgressBar
import androidx.recyclerview.widget.LinearLayoutManager
import androidx.recyclerview.widget.RecyclerView
import com.kotlinkatta.retrofitget.adapter.CommentsDataAdapter
import com.kotlinkatta.retrofitget.model.CommentsDataModel
import com.kotlinkatta.retrofitget.retofitdata.RetrofitClient
import kotlinx.android.synthetic.main.activity_main.*
import retrofit2.Call
import retrofit2.Callback
import retrofit2.Response

class MainActivity : AppCompatActivity() {
    lateinit var recyclerView: RecyclerView
    lateinit var layoutManager: LinearLayoutManager
    lateinit var progress_bar: ProgressBar

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        progress_bar = findViewById<ProgressBar>(R.id.progress_bar)
        recyclerView = findViewById<RecyclerView>(R.id.recyclerview)
        layoutManager = LinearLayoutManager(this)
        recyclerview.layoutManager = layoutManager

        funGetCommentsData()
    }

    private fun funGetCommentsData() {
        progress_bar.visibility = View.VISIBLE

        val call: Call<List<CommentsDataModel>> = RetrofitClient.getClient.getAllComments()
        call.enqueue(object : Callback<List<CommentsDataModel>> {

            override fun onResponse(call: Call<List<CommentsDataModel>>, response: Response<List<CommentsDataModel>>) {
                val adapter = CommentsDataAdapter(response.body()!!)
                recyclerView.adapter = adapter
                progress_bar.visibility = View.GONE
            }

            override fun onFailure(call: Call<List<CommentsDataModel>>, t: Throwable?) {
                progress_bar.visibility = View.GONE
            }
        })
    }
}
Step 9:
activity_main.xml
Add following code into activity_main.xml.
<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.widget.CoordinatorLayout
    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">

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/recyclerview"
        android:layout_width="match_parent"
        android:layout_height="match_parent">
    </androidx.recyclerview.widget.RecyclerView>

    <ProgressBar
        android:id="@+id/progress_bar"
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:layout_gravity="center"/>
</androidx.coordinatorlayout.widget.CoordinatorLayout>
OutPut:

Comments

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