Android 之 MVP架构

一、MVP架构分层与职责

二、项目结构与包组织 

├── contract
│   └── LoginContract.java       // 定义View和Presenter接口
├── model
│   ├── UserRepository.java      // 数据操作实现
│   └── OnLoginListener.java     // 登录回调接口
├── presenter
│   └── LoginPresenter.java      // 业务逻辑实现
└── view
└── LoginActivity.java       // 实现View接口，处理UI

三、详细代码实现

1. ​​Contract接口（contract/LoginContract.java）

public interface LoginContract {interface View {void showLoading();void hideLoading();void showUsernameError(String error);void showPasswordError(String error);void onLoginSuccess();void onLoginFailure(String error);}interface Presenter {void attachView(View view);void detachView();void login(String username, String password);}
}

作用​​：统一管理View和Presenter的接口，避免类膨胀

2. ​​Model层（model/UserRepository.java）​

public class UserRepository {// 模拟网络请求登录public void login(String username, String password, OnLoginListener listener) {// 实际开发中替换为Retrofit/Volley请求if ("admin".equals(username) && "123456".equals(password)) {listener.onSuccess();} else {listener.onFailure("用户名或密码错误");}}public interface OnLoginListener {void onSuccess();void onFailure(String errorMsg);}
}

​​职责​​：

• 数据验证、网络请求、数据库操作
• 通过回调接口OnLoginListener返回结果（避免直接依赖Presenter）

3. ​​Presenter层（presenter/LoginPresenter.java）

public class LoginPresenter implements LoginContract.Presenter {private LoginContract.View view;private UserRepository userRepository;public LoginPresenter() {userRepository = new UserRepository();}@Overridepublic void attachView(LoginContract.View view) {this.view = view;}@Overridepublic void detachView() {view = null; // 防止内存泄漏}@Overridepublic void login(String username, String password) {if (view == null) return;// 本地校验if (TextUtils.isEmpty(username)) {view.showUsernameError("用户名不能为空");return;}if (TextUtils.isEmpty(password)) {view.showPasswordError("密码不能为空");return;}view.showLoading();userRepository.login(username, password, new UserRepository.OnLoginListener() {@Overridepublic void onSuccess() {if (view != null) {view.hideLoading();view.onLoginSuccess();}}@Overridepublic void onFailure(String errorMsg) {if (view != null) {view.hideLoading();view.onLoginFailure(errorMsg);}}});}
}

关键逻辑​​：

• 持有View的弱引用（通过attachView/detachView管理）
• 本地验证 → 调用Model → 处理回调 → 更新View。

4. ​​View层（view/LoginActivity.java）

public class LoginActivity extends AppCompatActivity implements LoginContract.View {private EditText etUsername, etPassword;private Button btnLogin;private ProgressBar progressBar;private LoginPresenter presenter;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_login);etUsername = findViewById(R.id.et_username);etPassword = findViewById(R.id.et_password);btnLogin = findViewById(R.id.btn_login);progressBar = findViewById(R.id.progress_bar);presenter = new LoginPresenter();presenter.attachView(this);btnLogin.setOnClickListener(v -> {String username = etUsername.getText().toString().trim();String password = etPassword.getText().toString().trim();presenter.login(username, password);});}@Overrideprotected void onDestroy() {super.onDestroy();presenter.detachView(); // 解绑View，避免内存泄漏}// 实现View接口方法@Overridepublic void showLoading() {progressBar.setVisibility(View.VISIBLE);}@Overridepublic void hideLoading() {progressBar.setVisibility(View.GONE);}@Overridepublic void showUsernameError(String error) {etUsername.setError(error);}@Overridepublic void showPasswordError(String error) {etPassword.setError(error);}@Overridepublic void onLoginSuccess() {Toast.makeText(this, "登录成功", Toast.LENGTH_SHORT).show();startActivity(new Intent(this, HomeActivity.class));finish();}@Overridepublic void onLoginFailure(String error) {Toast.makeText(this, error, Toast.LENGTH_SHORT).show();}
}

四、总结：MVP vs MVC 优势