Simple Login Example in MVP

Required package structure

XML activity_login

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:gravity="center_vertical"
    android:orientation="vertical"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin">

    <EditText
        android:id="@+id/et_login_username"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="USERNAME" />

    <EditText
        android:id="@+id/et_login_password"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="PASSWORD" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">

        <Button
            android:id="@+id/btn_login_login"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginRight="4dp"
            android:layout_weight="1"
            android:text="Login" />

        <Button
            android:id="@+id/btn_login_clear"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginLeft="4dp"
            android:layout_weight="1"
            android:text="Clear" />
    </LinearLayout>

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="3dp"
        android:text="correct user: mvp, mvp" />

    <ProgressBar
        android:id="@+id/progress_login"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="40dp" />

</LinearLayout>

Activity Class LoginActivity.class

public class LoginActivity extends AppCompatActivity implements ILoginView, View.OnClickListener {
    private EditText editUser;
    private EditText editPass;
    private Button   btnLogin;
    private Button   btnClear;
    private ILoginPresenter loginPresenter;
    private ProgressBar progressBar;

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

        //find view
        editUser = (EditText) this.findViewById(R.id.et_login_username);
        editPass = (EditText) this.findViewById(R.id.et_login_password);
        btnLogin = (Button) this.findViewById(R.id.btn_login_login);
        btnClear = (Button) this.findViewById(R.id.btn_login_clear);
        progressBar = (ProgressBar) this.findViewById(R.id.progress_login);

        //set listener
        btnLogin.setOnClickListener(this);
        btnClear.setOnClickListener(this);

        //init
        loginPresenter = new LoginPresenterCompl(this);
        loginPresenter.setProgressBarVisiblity(View.INVISIBLE);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()){
            case R.id.btn_login_clear:
                loginPresenter.clear();
                break;
            case R.id.btn_login_login:
                loginPresenter.setProgressBarVisiblity(View.VISIBLE);
                btnLogin.setEnabled(false);
                btnClear.setEnabled(false);
                loginPresenter.doLogin(editUser.getText().toString(), editPass.getText().toString());
                break;
        }
    }

    @Override
    public void onClearText() {
        editUser.setText("");
        editPass.setText("");
    }

    @Override
    public void onLoginResult(Boolean result, int code) {
        loginPresenter.setProgressBarVisiblity(View.INVISIBLE);
        btnLogin.setEnabled(true);
        btnClear.setEnabled(true);
        if (result){
            Toast.makeText(this,"Login Success",Toast.LENGTH_SHORT).show();
        }
        else
            Toast.makeText(this,"Login Fail, code = " + code,Toast.LENGTH_SHORT).show();
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
    }

    @Override
    public void onSetProgressBarVisibility(int visibility) {
        progressBar.setVisibility(visibility);
    }
}

Creating an ILoginView Interface

Create an ILoginView interface for update info from Presenter under view folder as follows:

public interface ILoginView {
    public void onClearText();
    public void onLoginResult(Boolean result, int code);
    public void onSetProgressBarVisibility(int visibility);
}

Creating an ILoginPresenter Interface

Create an ILoginPresenter interface in order to communicate with LoginActivity (Views) and create the LoginPresenterCompl class for handling login functionality and reporting back to the Activity. The LoginPresenterCompl class implements the ILoginPresenter interface:

ILoginPresenter.class

public interface ILoginPresenter {
    void clear();
    void doLogin(String name, String passwd);
    void setProgressBarVisiblity(int visiblity);
}

LoginPresenterCompl.class

public class LoginPresenterCompl implements ILoginPresenter {
    ILoginView iLoginView;
    IUser user;
    Handler handler;

    public LoginPresenterCompl(ILoginView iLoginView) {
        this.iLoginView = iLoginView;
        initUser();
        handler = new Handler(Looper.getMainLooper());
    }

    @Override
    public void clear() {
        iLoginView.onClearText();
    }

    @Override
    public void doLogin(String name, String passwd) {
        Boolean isLoginSuccess = true;
        final int code = user.checkUserValidity(name,passwd);
        if (code!=0) isLoginSuccess = false;
        final Boolean result = isLoginSuccess;
        handler.postDelayed(new Runnable() {
            @Override
            public void run() {
                    iLoginView.onLoginResult(result, code);
            }
        }, 5000);
    }

    @Override
    public void setProgressBarVisiblity(int visiblity){
        iLoginView.onSetProgressBarVisibility(visiblity);
    }

    private void initUser(){
        user = new UserModel("mvp","mvp");
    }
}

Creating a UserModel

Create a UserModel which is like a Pojo class for LoginActivity. Create an IUser interface for Pojo validations:

UserModel.class

public class UserModel implements IUser {
String name;
String passwd;

public UserModel(String name, String passwd) {
    this.name = name;
    this.passwd = passwd;
}

@Override
public String getName() {
    return name;
}

@Override
public String getPasswd() {
    return passwd;
}

@Override
public int checkUserValidity(String name, String passwd){
    if (name==null||passwd==null||!name.equals(getName())||!passwd.equals(getPasswd())){
        return -1;
    }
    return 0;
}

IUser.class

public interface IUser {
    String getName();

    String getPasswd();

    int checkUserValidity(String name, String passwd);
}

MVP

A Model-view-presenter (MVP) is a derivation of the model–view–controller (MVC) architectural pattern. It is used mostly for building user interfaces and offers the following benefits:

Views are more separated from Models. The Presenter is the mediator between Model and View.
It is easier to create unit tests.
Generally, there is a one-to-one mapping between View and Presenter, with the possibility to use multiple Presenters for complex Views.

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