Android MVP Architecture Login example in the Model View Presenter (MVP) pattern
Example
Let's see MVP in action using a simple Login Screen. There are two Buttons—one for login action and another for a registration screen; two EditTexts—one for the email and the other for the password.
LoginFragment (The View)
public class LoginFragment extends Fragment implements LoginContract.PresenterToView, View.OnClickListener {
private View view;
private EditText email, password;
private Button login, register;
private LoginContract.ToPresenter presenter;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_login, container, false);
}
@Override
public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
email = (EditText) view.findViewById(R.id.email_et);
password = (EditText) view.findViewById(R.id.password_et);
login = (Button) view.findViewById(R.id.login_btn);
login.setOnClickListener(this);
register = (Button) view.findViewById(R.id.register_btn);
register.setOnClickListener(this);
presenter = new LoginPresenter(this);
presenter.isLoggedIn();
}
@Override
public void onLoginResponse(boolean isLoginSuccess) {
if (isLoginSuccess) {
startActivity(new Intent(getActivity(), MapActivity.class));
getActivity().finish();
}
}
@Override
public void onError(String message) {
Toast.makeText(getActivity(), message, Toast.LENGTH_SHORT).show();
}
@Override
public void isLoggedIn(boolean isLoggedIn) {
if (isLoggedIn) {
startActivity(new Intent(getActivity(), MapActivity.class));
getActivity().finish();
}
}
@Override
public void onClick(View view) {
switch (view.getId()) {
case R.id.login_btn:
LoginItem loginItem = new LoginItem();
loginItem.setPassword(password.getText().toString().trim());
loginItem.setEmail(email.getText().toString().trim());
presenter.login(loginItem);
break;
case R.id.register_btn:
startActivity(new Intent(getActivity(), RegisterActivity.class));
getActivity().finish();
break;
}
}
}
LoginPresenter (The Presenter)
public class LoginPresenter implements LoginContract.ToPresenter {
private LoginContract.PresenterToModel model;
private LoginContract.PresenterToView view;
public LoginPresenter(LoginContract.PresenterToView view) {
this.view = view;
model = new LoginModel(this);
}
@Override
public void login(LoginItem userCredentials) {
model.login(userCredentials);
}
@Override
public void isLoggedIn() {
model.isLoggedIn();
}
@Override
public void onLoginResponse(boolean isLoginSuccess) {
view.onLoginResponse(isLoginSuccess);
}
@Override
public void onError(String message) {
view.onError(message);
}
@Override
public void isloggedIn(boolean isLoggedin) {
view.isLoggedIn(isLoggedin);
}
}
LoginModel (The Model)
public class LoginModel implements LoginContract.PresenterToModel, ResponseErrorListener.ErrorListener {
private static final String TAG = LoginModel.class.getSimpleName();
private LoginContract.ToPresenter presenter;
public LoginModel(LoginContract.ToPresenter presenter) {
this.presenter = presenter;
}
@Override
public void login(LoginItem userCredentials) {
if (validateData(userCredentials)) {
try {
performLoginOperation(userCredentials);
} catch (JSONException e) {
e.printStackTrace();
}
} else {
presenter.onError(BaseContext.getContext().getString(R.string.error_login_field_validation));
}
}
@Override
public void isLoggedIn() {
DatabaseHelper database = new DatabaseHelper(BaseContext.getContext());
presenter.isloggedIn(database.isLoggedIn());
}
private boolean validateData(LoginItem userCredentials) {
return Patterns.EMAIL_ADDRESS.matcher(userCredentials.getEmail()).matches()
&& !userCredentials.getPassword().trim().equals("");
}
private void performLoginOperation(final LoginItem userCredentials) throws JSONException {
JSONObject postData = new JSONObject();
postData.put(Constants.EMAIL, userCredentials.getEmail());
postData.put(Constants.PASSWORD, userCredentials.getPassword());
JsonObjectRequest request = new JsonObjectRequest(Request.Method.POST, Url.AUTH, postData,
new Response.Listener<JSONObject>() {
@Override
public void onResponse(JSONObject response) {
try {
String token = response.getString(Constants.ACCESS_TOKEN);
DatabaseHelper databaseHelper = new DatabaseHelper(BaseContext.getContext());
databaseHelper.login(token);
Log.d(TAG, "onResponse: " + token);
} catch (JSONException e) {
e.printStackTrace();
}
presenter.onLoginResponse(true);
}
}, new ErrorResponse(this));
RequestQueue queue = Volley.newRequestQueue(BaseContext.getContext());
queue.add(request);
}
@Override
public void onError(String message) {
presenter.onError(message);
}
}
Class Diagram
Let's see the action in the form of class diagram.
Notes:
- This example uses Volley for network communication, but this library is not required for MVP
UrlUtilsis a class which contains all the links for my API EndpointsResponseErrorListener.ErrorListeneris aninterfacethat listens for error inErrorResponsethatimplementsVolley'sResponse.ErrorListener; these classes are not included here as they are not directly part of this example
