Kotlin Call Service Using Retrofit2 Method Post Example

In this example, I will show you how to call json service using Retrofit2 to post user data and display response into TextView.

Kotlin Call Service Using Retrofit2 Method Post 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://reqres.in/api/users

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'

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("createdAt")
    val createdAt: String? = null,
)
Step 4:
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.Field
import retrofit2.http.FormUrlEncoded
import retrofit2.http.POST

interface DataService {
    @POST("/api/users")
    @FormUrlEncoded
    fun savePost(
        @Field("title") title: String,
        @Field("body") body: String,
        @Field("userId") userId: Long
    ): Call<UsersDataModel>
}
Step 5:
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://reqres.in"
    val retrofitInstance: Retrofit
        get() {
            if (retrofit == null) {
                retrofit = Retrofit.Builder()
                    .baseUrl(base_url)
                    .addConverterFactory(GsonConverterFactory.create())
                    .build()
            }
            return retrofit!!
        }
}
Step 6:
MainActivity.kt
Add following code into MainActivity.kt.
package com.kotlinkatta.retrofitpost

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.view.View
import android.widget.ProgressBar
import android.widget.TextView
import android.widget.Toast
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 txt_response: TextView
    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)
        txt_response = findViewById<TextView>(R.id.txt_response)

        funPostUsersData()
    }

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

        val service: DataService = RetrofitClient.retrofitInstance!!.create(DataService::class.java)
        val call: Call<UsersDataModel> = service.savePost("title","body",1)
        call.enqueue(object : Callback<UsersDataModel> {

            override fun onResponse(call: Call<UsersDataModel>, response: Response<UsersDataModel>) {
                Toast.makeText(applicationContext,"Data Send Successfully",Toast.LENGTH_SHORT).show()
                txt_response.setText("Id : "+response.body()!!.id +"\nCreated At : "+response.body()!!.createdAt)
                progress_bar.visibility = View.GONE
            }

            override fun onFailure(call: Call<UsersDataModel>, t: Throwable?) {
                progress_bar.visibility = View.GONE
            }
        })
    }
}
Step 7:
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">

    <TextView
        android:id="@+id/txt_response"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:text=""
        android:layout_gravity="center"
        android:gravity="center"
        android:textSize="20dp"/>

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