MVPC (semi- MVVM) implementation for Android app Development

Introduction

When I was trying to implement MVC for Android Application, the concept of “Observer” really attracts me. It really put me in a situation, where, I have to think, should I go for MVC or MVPC.  Because, I think, MVPC would be more organized and maintainable way for this Android application.  Along with this thinking, possibility of total segregation of event listeners in code, make me think about MVPC for this project seriously.

[Note: Observer is the interface to be implemented by objects that receive notification of updates on an Observable object. (Observer Triggers, when Observable notifies any changes on it)]

Why MVPC?

Model-View-Presenter-Controller. In MVC, View notifies Controller, Controller notifies Model, and Model notifies View. It is really very compact and smart enough Architecture. But, Presenter is another useful architecture entity. It will give another level of abstraction to the project between View and Controller. This will make the view much independent and make controller more flexible.  With this architecture, we can replace the existing view with a new one, so smartly, that we may have to do no changes in Controller.

Do we really need MVPC in Android Application?
We may not need MVPC for today or tomorrow, but day after tomorrow. As year goes, a View of an application becomes monotonous to the user, or else, we may need to implement different views (Theme) to the project. To do all the above, we really don’t want to hamper any application flow.  MVPC will be one of the best fit architecture for this.

Code Example-
In MainActivity.java-

public class MainActivity extends Activity  {

       public User mUser;

       UserController controller;

       UserPresenter presenter;

      

       @Override

       protected void onCreate(Bundle savedInstanceState) {

              super.onCreate(savedInstanceState);

              setContentView(R.layout.activity_main);

              mUser= new User();

              controller= new UserController(this);

              mUser.addObserver(controller);

              presenter= new UserPresenter(mUser);

             

              Button test_btn=(Button) findViewById(R.id.btn_Test);

              Button test_btn2=(Button) findViewById(R.id.btn_Test2);

              test_btn.setOnClickListener(presenter);

              test_btn2.setOnClickListener(presenter);

       }

In UserPresenter.java-

public class UserPresenter implements OnClickListener {

       private User _model;

       public UserPresenter(User model)

       {

              _model=model;

       }

      

       @Override

       public void onClick(View v) {

              switch(v.getId())

              {

              case R.id.btn_Test:

                     _model.setCount();

                     break;

              case R.id.btn_Test2:

                     _model.setCount();

                     _model.setCount();

                     break;

             

              }

       }

}

In UserModel.java-

public class User extends Observable {

       public int count=0;

       public User(){

             

       }

       public void setCount()

       {

              count++;

              setChanged();

              notifyObservers();

       }

}                     

In UserController.java-

public class UserController implements Observer {

    public User mUser;

    private Activity _act;

    public UserController(Activity act )

    {

       _act=act;

    }

   

       @Override

       public void update(Observable observable, Object data) {

              TextView lbl= (TextView)_act.findViewById(R.id.lbl_Text);

              lbl.setText(""+((MainActivity)_act).mUser.getCount());

       }

}