Kotlin Call Service using Retrofit2 and MutableList Example

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

Kotlin Call Service Using Retrofit2 And MutableList Example Video

  • You can also go through this video explanation.

Kotlin Call Service Using Retrofit2 And MutableList  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/users

JSON service output screen:-



Step 1:
Open build.gradle and add following dependency and rebuild the project.
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
UsersDataModel.kt
Create new class UsersDataModel.kt under model package and Add following code.
package com.kotlinkatta.retrofitget.model

import com.google.gson.annotations.SerializedName

data class UsersDataModel(
    @SerializedName("id")
    val id: Int? = null,

    @SerializedName("name")
    val name: String? = null,

    @SerializedName("username")
    val userName: String? = null,

    @SerializedName("email")
    val email: String? = null,

    @SerializedName("address")
    val addressObject : address? = null,

    @SerializedName("phone")
    val phone: String? = null,

    @SerializedName("website")
    val website: String? = null,

    @SerializedName("company")
    val companyObject : company? = null,
)

data class address(
    @SerializedName("street")
    val street: String? = null,

    @SerializedName("suite")
    val suite: String? = null,

    @SerializedName("city")
    val city: String? = null,

    @SerializedName("zipcode")
    val zipCode: String? = null,

    @SerializedName("geo")
    val geoObject : geo? = null,
)

data class geo(
    @SerializedName("lat")
    val lat: String? = null,

    @SerializedName("lng")
    val lng: String? = null,
)

data class company(
    @SerializedName("name")
    val name: String? = null,

    @SerializedName("catchPhrase")
    val catchPhrase: String? = null,

    @SerializedName("bs")
    val bs: String? = null,
)
Step 4:
Create new Layout:- users_data_row.xml
Create new users_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:layout_marginTop="3dp"
                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:justificationMode="inter_word"
                android:textSize="20dp" />

            <TextView
                android:layout_marginTop="3dp"
                android:id="@+id/txt_address_city"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:justificationMode="inter_word"
                android:textSize="20dp" />

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

            <TextView
                android:layout_marginTop="3dp"
                android:id="@+id/txt_company_name"
                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
UsersDataAdapter.kt
Create new class UsersDataAdapter.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.retofitokhttpmutableget.R
import com.kotlinkatta.retrofitget.model.UsersDataModel
import kotlinx.android.synthetic.main.users_data_row.view.*

class UsersDataAdapter(private var userList: MutableList<UsersDataModel>) : RecyclerView.Adapter<UsersDataAdapter.ViewHolder>() {

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

    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
        val usersDataModel : UsersDataModel = userList[position]
        holder.txt_name.text = "Name : " + usersDataModel.name
        holder.txt_email.text = "Email : " + usersDataModel.email
        holder.txt_address_city.text = "Address City : " + usersDataModel.addressObject!!.city
        holder.txt_geo_lat_lng.text = "Geo Lat : " + usersDataModel.addressObject!!.geoObject!!.lat + " " + "Lat : " + usersDataModel.addressObject!!.geoObject!!.lng
        holder.txt_company_name.text = "Company Name : " + usersDataModel.companyObject!!.name
    }

    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_address_city = itemView.txt_address_city
        val txt_geo_lat_lng = itemView.txt_geo_lat_lng
        val txt_company_name = itemView.txt_company_name
    }
}
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.UsersDataModel
import retrofit2.Call
import retrofit2.http.GET

interface DataService {
    @GET("/users")
    fun getUsersData(): Call<MutableList<UsersDataModel>>
}
Step 7:
RetrofitClient.kt
Create new class RetrofitClient.kt under retofitdata package and Add following code.
package com.kotlinkatta.retrofitget.retofitdata

import retrofit2.Retrofit
import retrofit2.converter.gson.GsonConverterFactory

object RetrofitClient {
    var retrofit: Retrofit? = null
    var base_url = "https://jsonplaceholder.typicode.com"
    val retrofitInstance: Retrofit
        get() {
            if (retrofit == null) {
                retrofit = Retrofit.Builder()
                    .baseUrl(base_url)
                    .addConverterFactory(GsonConverterFactory.create())
                    .build()
            }
            return retrofit!!
        }
}
Step 8:
MainActivity.kt
Add following code into MainActivity.kt.
package com.kotlinkatta.retofitgetmutablelist

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.UsersDataAdapter
import com.kotlinkatta.retrofitget.model.UsersDataModel
import com.kotlinkatta.retrofitget.retofitdata.DataService
import com.kotlinkatta.retrofitget.retofitdata.RetrofitClient
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

    var listUsers: MutableList<UsersDataModel> = mutableListOf<UsersDataModel>()

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

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

        funGetUsersData()
    }

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

        val service: DataService = RetrofitClient.retrofitInstance!!.create(DataService::class.java)
        val call: Call<MutableList<UsersDataModel>> = service.getUsersData()
        call.enqueue(object : Callback<MutableList<UsersDataModel>> {

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

            override fun onFailure(call: Call<MutableList<UsersDataModel>>, 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:

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