Login with Retrofit in android Studio with SourceCode | Login and Registration form in android using JSON example

 Build.gradle File:-  

implementation 'com.google.android.material:material:1.3.0'
implementation 'com.squareup.retrofit2:retrofit:2.8.1'
implementation 'com.squareup.retrofit2:converter-gson:2.8.1'
implementation 'com.squareup.okhttp3:logging-interceptor:4.6.0'

 Activity-main 

<?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"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:orientation="vertical"
    android:background="@color/colorWhite"
    android:layout_height="match_parent"
    tools:context=".MainActivity">
<TextView
    android:layout_width="wrap_content"
    android:text="Login to continue"
    android:layout_marginTop="100dp"
    android:textSize="24sp"
    android:layout_gravity="center_horizontal"
    android:textColor="@color/colorPrimaryDark"
    android:layout_height="wrap_content" />

    <com.google.android.material.textfield.TextInputLayout
        android:layout_width="match_parent"
        android:layout_marginTop="30dp"
        android:layout_marginStart="30dp"
        android:layout_marginEnd="30dp"
        android:hint="Username"
        android:layout_height="wrap_content">

        <com.google.android.material.textfield.TextInputEditText
            android:layout_width="match_parent"
            android:inputType="text"
            android:id="@+id/edUsername"
            android:layout_height="wrap_content" />

    </com.google.android.material.textfield.TextInputLayout>
    <com.google.android.material.textfield.TextInputLayout
        android:layout_width="match_parent"
        android:layout_marginTop="30dp"
        android:hint="Password"
        android:layout_marginStart="30dp"
        android:layout_marginEnd="30dp"
        android:layout_height="wrap_content">
        <com.google.android.material.textfield.TextInputEditText
            android:layout_width="match_parent"
            android:inputType="textPassword"
            android:id="@+id/edPassword"
            android:layout_height="wrap_content" />
    </com.google.android.material.textfield.TextInputLayout>
    <Button
        android:layout_width="match_parent"
        android:layout_margin="30dp"
        android:text="Login"
        android:id="@+id/btnLogin"
        android:background="@color/colorPrimary"
        android:textColor="@color/colorWhite"
        android:layout_height="wrap_content" />
</LinearLayout> 

 Java File :-

1. Api Client 

import okhttp3.OkHttpClient;
import okhttp3.logging.HttpLoggingInterceptor;
import retrofit2.Retrofit;
import retrofit2.converter.gson.GsonConverterFactory;

public class ApiClient {

    private static Retrofit getRetrofit(){

        HttpLoggingInterceptor httpLoggingInterceptor = new HttpLoggingInterceptor();
        httpLoggingInterceptor.setLevel(HttpLoggingInterceptor.Level.BODY);

        OkHttpClient okHttpClient = new OkHttpClient.Builder().addInterceptor(httpLoggingInterceptor).build();

        Retrofit retrofit = new Retrofit.Builder()
                .addConverterFactory(GsonConverterFactory.create())
                .baseUrl("http://api.irawen.net/")  //Change server URL
                .client(okHttpClient)
                .build();

        return retrofit;
    }


    public static UserService getUserService(){
        UserService userService = getRetrofit().create(UserService.class);

        return userService;
    }

}

2. Login Request :-

public class LoginRequest {

    private String username;
    private String password;

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }
}

3. Login response :- 

public class LoginResponse {


    private int user_id;
    private String email;
    private String username;

    public int getUser_id() {
        return user_id;
    }

    public void setUser_id(int user_id) {
        this.user_id = user_id;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }
}

4. Main Activity :-

 import android.content.Intent;
import android.os.Bundle;
import android.os.Handler;
import android.text.TextUtils;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

import com.google.android.material.textfield.TextInputEditText;

import androidx.appcompat.app.AppCompatActivity;
import retrofit2.Call;
import retrofit2.Callback;
import retrofit2.Response;

public class MainActivity extends AppCompatActivity {


    TextInputEditText username, password;
    Button btnLogin;

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

        username = findViewById(R.id.edUsername);
        password = findViewById(R.id.edPassword);
        btnLogin = findViewById(R.id.btnLogin);

        btnLogin.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

                if(TextUtils.isEmpty(username.getText().toString()) || TextUtils.isEmpty(password.getText().toString())){
                    Toast.makeText(MainActivity.this,"Username / Password Required", Toast.LENGTH_LONG).show();
                }else{
                    //proceed to login
                    login();
                }

            }
        });
   }


   public void login(){
      LoginRequest loginRequest = new LoginRequest();
      loginRequest.setUsername(username.getText().toString());
      loginRequest.setPassword(password.getText().toString());

      Call<LoginResponse> loginResponseCall = ApiClient.getUserService().userLogin(loginRequest);
      loginResponseCall.enqueue(new Callback<LoginResponse>() {
          @Override
          public void onResponse(Call<LoginResponse> call, Response<LoginResponse> response) {

              if(response.isSuccessful()){
                  Toast.makeText(MainActivity.this,"Login Successful", Toast.LENGTH_LONG).show();
                  LoginResponse loginResponse = response.body();

                  new Handler().postDelayed(new Runnable() {
                      @Override
                      public void run() {

                        startActivity(new Intent(MainActivity.this,DashboardActivity.class).putExtra("data",loginResponse.getUsername()));
                      }
                  },700);

              }else{
                  Toast.makeText(MainActivity.this,"Login Failed", Toast.LENGTH_LONG).show();

              }

          }

          @Override
          public void onFailure(Call<LoginResponse> call, Throwable t) {
              Toast.makeText(MainActivity.this,"Throwable "+t.getLocalizedMessage(), Toast.LENGTH_LONG).show();

          }
      });


   }

}

5. User Service :-

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

public interface UserService {


    @POST("authenticate/")
 Call<LoginResponse> userLogin(@Body LoginRequest loginRequest);


}