Android MVP for Beginners with Sample Application

Learn Android MVP Basics and Create Sample App

This article is for beginners who wants to use Android MVP. So we have created a small sample app that will help you to create your first app using MVP structure.

Why do we need MVP or any structure?

While working with any long-term project, it needs to be scalable, less complicated. MVP makes it possible by dividing code structure into three different layers (MODEL – PRESENTER – VIEW).

Let’s Understand how this will work:

Lets visually represent how it looks:

Let’s create Login screen.

public class PreferencesProvider{ 

private static String SHARED_PREFERENCES = "mvpPreferences";

private static SharedPreferences sPreferences;

public static SharedPreferences providePreferences() {
       return sPreferences;
   }
 public static void init(Context context) {
       sPreferences = context.getSharedPreferences(SHARED_PREFERENCES, Context.MODE_PRIVATE);
   }
}

public class App extends Application {
   @Override
   public void onCreate() {
       super.onCreate();
       PreferencesProvider.init(this);
   }
}

public interface UserPreferences {
   String IS_USER_LOGIN = "isUserLogin";
   public void setUserLogin(boolean status);
   public boolean isUserLogin();
   public void clearUser();
   void removeNote(Note note);
}

import android.content.SharedPreferences;
import android.text.TextUtils;
import mvpdemo.rajnit.com.mvpblogdemo.data.models.Note;

public class UserPreferencesImpl implements UserPreferences {
   protected SharedPreferences mPreferences;
   public UserPreferencesImpl() {
       this.mPreferences = PreferencesProvider.providePreferences();
   }
   @Override
   public boolean isUserLogin() {
       return mPreferences.getBoolean(IS_USER_LOGIN, false);
   }
   @Override
   public void setUserLogin(boolean status) {
       mPreferences.edit().putBoolean(IS_USER_LOGIN, status).apply();
   }
   @Override
   public void clearUser() {
       mPreferences.edit()
               .putBoolean(IS_USER_LOGIN, false)
               .apply();
   }
}

Now we will create login screen activity.

import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import mvpdemo.rajnit.com.mvpblogdemo.R;
import mvpdemo.rajnit.com.mvpblogdemo.presenter.LoginPresenter;
import mvpdemo.rajnit.com.mvpblogdemo.presenter.Presenter;
import mvpdemo.rajnit.com.mvpblogdemo.view.activities.views.LoginActivityView;

public class LoginActivity extends AbstractActivity implements LoginActivityView {
   private EditText edtUserName, edtPassword;
   private Button btnLogin;

   private LoginPresenter mPresenter = new LoginPresenter(this);

   @Override
   protected void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.activity_login);
       edtUserName = findViewById(R.id.edtUserName);
       edtPassword = findViewById(R.id.edtPassword);
       btnLogin = findViewById(R.id.btnLogin);
       initListeners();
       mPresenter.onCreate(getIntent());
   }

   private void initListeners() {
       btnLogin.setOnClickListener(new View.OnClickListener() {
           @Override
           public void onClick(View v) {
               mPresenter.login(edtUserName.getText().toString(), edtPassword.getText().toString());
           }
       });
   }

   @Override
   Presenter getPresenter() {
       return mPresenter;
   }

   @Override
   public void showMainActivity() {
       startActivity(new Intent(LoginActivity.this,MainActivity.class));
       overridePendingTransition(R.anim.fade_in,R.anim.fade_out);
       finish();
   }

   @Override
   public void showError(String errorMsg) {
       showToast(errorMsg);
   }

}

Now we will create LoginActivityView interface (As View).

public interface LoginActivityView {
   void showMainActivity();
   void showError(String errorMsg);
}

⇒ Now create LoginPresenter class (As Presenter).
LoginPresenter.java
public class LoginPresenter extends AbstractPresenter {
   private LoginActivityView mView;
   UserPreferences mDatabase = new UserPreferencesImpl();

   public LoginPresenter(LoginActivityView mView) {
       this.mView = mView;
   }

   public void onCreate(Intent intent) {
       // Handle intent data here...
   }

   public void login(String username, String password) {
       if(TextUtils.isEmpty(username)){
           mView.showError("Please enter username");
       }else if(username.length() < 6){
           mView.showError("Username must contains 6 letters");
       }else if(TextUtils.isEmpty(password)){
           mView.showError("Please enter password");
       }else if(password.length() < 6){
           mView.showError("Password must contains 6 letters");
       }else {
           mDatabase.setUserLogin(true);
           mView.showMainActivity();
       }
   }
}

Let’s check how code flow works:

1. 1. LoginActivity implements LoginActivityView interface and @override its methods.

public class LoginActivity extends AbstractActivity implements LoginActivityView

1. 1. We initialize LoginPresenter in LoginActivity and pass LoginActivityView reference in constructor.

private LoginPresenter mPresenter = new LoginPresenter(this);

1. 1. When you click on login button it triggers login click event and calls presenter login method.

btnLogin.setOnClickListener(new View.OnClickListener() {
           @Override
           public void onClick(View v) {
               mPresenter.login(edtUserName.getText().toString(), edtPassword.getText().toString());
           }
       });

1. 1. Login method in presenter will check if  username and password are valid or not.

public void login(String username, String password) {
   if(TextUtils.isEmpty(username)){
       mView.showError("Please enter username");
   }else if(username.length() < 6){
       mView.showError("Username must contains 6 letters");
   }else if(TextUtils.isEmpty(password)){
       mView.showError("Please enter password");
   }else if(password.length() < 6){
       mView.showError("Password must contains 6 letters");
   }else {
       mDatabase.setUserLogin(true);
       mView.showMainActivity();
   }
}

1. 1. If username or password is incorrect then trigger showError() method and it gives callback in LoginActivity.

public void showError(String errorMsg) {
  if (errorMsg == null || errorMsg.isEmpty()) return;
  Toast.makeText(this, errorMsg, Toast.LENGTH_LONG).show();
}

1. 1. If username and password is correct then it will update status in local storage.

mDatabase.setUserLogin(true);
mView.showMainActivity();

1. 1. Below method is to get callback in loginActivity.

public void showMainActivity() {
   startActivity(new Intent(LoginActivity.this,MainActivity.class));
   overridePendingTransition(R.anim.fade_in,R.anim.fade_out);
   finish();
}

That’s it. We have created the login screen using MVP structure.

You can check out our Github Repo for full app development.