<!--permissions for INTERNET-->
<uses-permission android:name="android.permission.INTERNET"/>

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <!--edit text field for adding name-->
    <EditText
        android:id="@+id/idEdtName"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="10dp"
        android:layout_marginTop="40dp"
        android:hint="Enter your name" />

    <!--edit text for adding job-->
    <EditText
        android:id="@+id/idEdtJob"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="10dp"
        android:hint="Enter your job" />

    <!--button for adding data-->
    <Button
        android:id="@+id/idBtnPost"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="20dp"
        android:text="Send Data to API"
        android:textAllCaps="false" />

    <!--text view for displaying our API response-->
    <TextView
        android:id="@+id/idTVResponse"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="10dp"
        android:gravity="center_horizontal"
        android:text="Response"
        android:textAlignment="center"
        android:textSize="15sp" />

    <!--progress bar for loading -->
    <ProgressBar
        android:id="@+id/idLoadingPB"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:visibility="gone" />

</LinearLayout>

public class DataModal {

    // string variables for our name and job
    private String name;
    private String job;

    public DataModal(String name, String job) {
        this.name = name;
        this.job = job;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getJob() {
        return job;
    }

    public void setJob(String job) {
        this.job = job;
    }

}

import retrofit2.Call;
import retrofit2.http.Body;
import retrofit2.http.POST;

public interface RetrofitAPI {

    // as we are making a post request to post a data
    // so we are annotating it with post
    // and along with that we are passing a parameter as users
    @POST("users")

    //on below line we are creating a method to post our data.
    Call<DataModal> createPost(@Body DataModal dataModal);
}

import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.Toast;

import androidx.appcompat.app.AppCompatActivity;

import retrofit2.Call;
import retrofit2.Callback;
import retrofit2.Response;
import retrofit2.Retrofit;
import retrofit2.converter.gson.GsonConverterFactory;

public class MainActivity extends AppCompatActivity {

    // creating variables for our edittext, 
    // button, textview and progressbar.
    private EditText nameEdt, jobEdt;
    private Button postDataBtn;
    private TextView responseTV;
    private ProgressBar loadingPB;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // initializing our views
        nameEdt = findViewById(R.id.idEdtName);
        jobEdt = findViewById(R.id.idEdtJob);
        postDataBtn = findViewById(R.id.idBtnPost);
        responseTV = findViewById(R.id.idTVResponse);
        loadingPB = findViewById(R.id.idLoadingPB);

        // adding on click listener to our button.
        postDataBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // validating if the text field is empty or not.
                if (nameEdt.getText().toString().isEmpty() && jobEdt.getText().toString().isEmpty()) {
                    Toast.makeText(MainActivity.this, "Please enter both the values", Toast.LENGTH_SHORT).show();
                    return;
                }
                // calling a method to post the data and passing our name and job.
                postData(nameEdt.getText().toString(), jobEdt.getText().toString());
            }
        });
    }

    private void postData(String name, String job) {

        // below line is for displaying our progress bar.
        loadingPB.setVisibility(View.VISIBLE);

        // on below line we are creating a retrofit 
        // builder and passing our base url
        Retrofit retrofit = new Retrofit.Builder()
                .baseUrl("https://reqres.in/api/")
                // as we are sending data in json format so 
                // we have to add Gson converter factory
                .addConverterFactory(GsonConverterFactory.create())
                // at last we are building our retrofit builder.
                .build();
        // below line is to create an instance for our retrofit api class.
        RetrofitAPI retrofitAPI = retrofit.create(RetrofitAPI.class);

        // passing data from our text fields to our modal class.
        DataModal modal = new DataModal(name, job);

        // calling a method to create a post and passing our modal class.
        Call<DataModal> call = retrofitAPI.createPost(modal);

        // on below line we are executing our method.
        call.enqueue(new Callback<DataModal>() {
            @Override
            public void onResponse(Call<DataModal> call, Response<DataModal> response) {
                // this method is called when we get response from our api.
                Toast.makeText(MainActivity.this, "Data added to API", Toast.LENGTH_SHORT).show();

                // below line is for hiding our progress bar.
                loadingPB.setVisibility(View.GONE);

                // on below line we are setting empty text
                // to our both edit text.
                jobEdt.setText("");
                nameEdt.setText("");

                // we are getting response from our body 
                // and passing it to our modal class.
                DataModal responseFromAPI = response.body();

                // on below line we are getting our data from modal class and adding it to our string.
                String responseString = "Response Code : " + response.code() + "\nName : " + responseFromAPI.getName() + "\n" + "Job : " + responseFromAPI.getJob();

                // below line we are setting our 
                // string to our text view.
                responseTV.setText(responseString);
            }

            @Override
            public void onFailure(Call<DataModal> call, Throwable t) {
                // setting text to our text view when 
                // we get error response from API.
                responseTV.setText("Error found is : " + t.getMessage());
            }
        });
    }
}