Android: MVP mode example

Here is a small example.
layout_main.xml

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

    <EditText
        android:id="@+id/username"
        android:layout_width="match_parent"
        android:layout_height="50dp" />
    
    <EditText
        android:id="@+id/password"
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:inputType="numberPassword" />

    <Button
        android:id="@+id/login"
        android:layout_width="match_parent"
        android:layout_height="50dp" />

    <TextView
        android:id="@+id/show"
        android:layout_width="match_parent"
        android:layout_height="50dp" />
</LinearLayout>

What needs to be done is that the user enters the username and password, and after clicking the login button, the login failure or login success will be displayed in the show control.

Model layer interface:

public interface IMainModel {
    boolean login(String username, String password);
}

Model layer implementation:

public class MainModel implements IMainModel {

    @Override
    public boolean login(String username, String password) {
        // 模拟网络，进行耗时操作
        try {
            Thread.sleep(3000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        if(username.equals(password))
            return true;
        return false;
    }

}

If the user name and password are the same, the login is successful, otherwise the login fails.

View layer interface:

public interface IMainView {
    void show(String s);
}

Presenter layer implementation:

import android.os.Handler;

public class MainPresenter {

    private IMainModel model;
    private IMainView view;
    private Handler handler = new Handler();

    public MainPresenter() {
        model = new MainModel();
    }

    public void setView(IMainView iUserView) {
        this.view = iUserView;
    }

    // 使用handler开启子线程
    public void login(final String username, final String password) {

        handler.post(new Runnable() {
            @Override
            public void run() {
                if (model.login(username, password)) {
                    view.show("登陆成功");
                } else {
                    view.show("登陆失败");
                }
            }
        });


    }

}

Since Activity acts as the view layer, it implements the view layer interface. And holds the presenter object.
MainActivity.java:

public class MainActivity extends Activity implements View.OnClickListener , IMainView {

    private EditText username, password;
    private Button button;
    private TextView show;
    private MainPresenter presenter;

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

        presenter = new MainPresenter();
        // 将view层传入
        presenter.setView(this);

        username = (EditText) this.findViewById(R.id.username);
        password = (EditText) this.findViewById(R.id.password);
        button = (Button) this.findViewById(R.id.login);
        show = (TextView) this.findViewById(R.id.show);

        button.setOnClickListener(this);
    }


    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.login:
                String userName = username.getText().toString();
                String passWord = password.getText().toString();
                presenter.login(userName, passWord);
                break;
        }
    }

    @Override
    public void show(String s) {
        show.setText(s);
    }
}

This implementation can make the Activity less bloated. The coupling is low and low. It's a bit similar to the observer mode.