MVP是我最喜欢的用于创建UI的设计模式。
MVP和MVC之间的最大区别在于如何处理视图。
- 在MVC中，控制器会操纵视图，并注意如何在视图中呈现用户操作和模型的一部分。这意味着Controller和View具有“紧密耦合”。
- 在MVP中，Presenter负责用户任务，该模型在Presenter和View之间共享。因此，视图根据模型呈现UI，有时视图可以具有要从Presenter调用的动作。Presenter和View可以具有定义的接口协定，以使其“松散耦合”。例如，您可以为Java Swing UI创建一个视图，为JavaFX UI创建另一个视图。或者，如果与数据源的连接发生更改，则只需更新演示者。
对MVP进行编程的样式很多。
以正式的方式，包括为设计模式的每个元素创建接口。
import javax.swing.JOptionPane;interface LoginModel { String getUser(); void setUser(String user);}class MyLoginModel implements LoginModel { String user; @Override public String getUser() { return user; } @Override public void setUser(String user) { this.user = user; }}interface LoginView { LoginPresenter getPresenter(); void setPresenter(LoginPresenter loginPresenter); void updateModelFromView(); void updateViewFromModel(); void open(); void close(); void userRejected();}class MyLoginView extends javax.swing.Jframe implements LoginView { private LoginPresenter loginPresenter; public MyLoginView() { initComponents(); } @SuppressWarnings("unchecked") private void initComponents() { java.awt.GridBagConstraints gridBagConstraints; jLabel1 = new javax.swing.JLabel(); jTextField1 = new javax.swing.JTextField(); jLabel2 = new javax.swing.JLabel(); jButton1 = new javax.swing.JButton(); setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE); setBounds(new java.awt.Rectangle(0, 0, 0, 0)); java.awt.GridBagLayout layout = new java.awt.GridBagLayout(); layout.columnWidths = new int[] {0, 7, 0}; layout.rowHeights = new int[] {0, 7, 0, 7, 0}; getContentPane().setLayout(layout); jLabel1.setFont(new java.awt.Font("Tahoma", 1, 11)); // NOI18N jLabel1.setText("Welcome"); gridBagConstraints = new java.awt.GridBagConstraints(); gridBagConstraints.gridx = 0; gridBagConstraints.gridy = 0; gridBagConstraints.gridwidth = 3; getContentPane().add(jLabel1, gridBagConstraints); jTextField1.setColumns(13); gridBagConstraints = new java.awt.GridBagConstraints(); gridBagConstraints.gridx = 2; gridBagConstraints.gridy = 2; gridBagConstraints.fill = java.awt.GridBagConstraints.HORIZONTAL; getContentPane().add(jTextField1, gridBagConstraints); jLabel2.setText("User"); gridBagConstraints = new java.awt.GridBagConstraints(); gridBagConstraints.gridx = 0; gridBagConstraints.gridy = 2; getContentPane().add(jLabel2, gridBagConstraints); jButton1.setText("Login"); jButton1.addActionListener(new java.awt.event.ActionListener() { public void actionPerformed(java.awt.event.ActionEvent evt) { jButton1ActionPerformed(evt); } }); gridBagConstraints = new java.awt.GridBagConstraints(); gridBagConstraints.gridx = 2; gridBagConstraints.gridy = 4; getContentPane().add(jButton1, gridBagConstraints); pack(); } private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) { getPresenter().login(); } private javax.swing.JButton jButton1; private javax.swing.JLabel jLabel1; private javax.swing.JLabel jLabel2; private javax.swing.JTextField jTextField1; @Override public void updateModelFromView() { getPresenter().getModel().setUser(jTextField1.getText()); } @Override public void updateViewFromModel() { jTextField1.setText(getPresenter().getModel().getUser()); } @Override public void open() { setVisible(true); jTextField1.selectAll(); jTextField1.requestFocus(); } @Override public void close() { dispose(); } @Override public void userRejected() { jLabel1.setText("Try again!"); jTextField1.selectAll(); jTextField1.requestFocus(); } @Override public LoginPresenter getPresenter() { return loginPresenter; } @Override public void setPresenter(LoginPresenter loginPresenter) { this.loginPresenter = loginPresenter; }}interface LoginPresenter { LoginModel getModel(); void setModel(LoginModel loginModel); LoginView getView(); void setView(LoginView loginView); void setonLogin(Runnable onLogin); void run(); void login();}class MyLoginPresenter implements LoginPresenter { LoginModel loginModel; LoginView loginView; private Runnable onLogin; @Override public LoginModel getModel() { return loginModel; } @Override public void setModel(LoginModel loginModel) { this.loginModel = loginModel; } @Override public LoginView getView() { return loginView; } @Override public void setView(LoginView loginView) { this.loginView = loginView; } @Override public void setonLogin(Runnable onLogin) { this.onLogin = onLogin; } @Override public void run() { loginModel.setUser("previousUser"); loginView.setPresenter(this); loginView.updateViewFromModel(); loginView.open(); } @Override public void login() { loginView.updateModelFromView(); if (loginModel.getUser().equalsIgnoreCase("root")) { loginView.close(); loginView.setPresenter(null);// for memory sanity. onLogin.run(); } else { loginView.userRejected(); } }}public class Application { public static void main(String args[]) { java.awt.EventQueue.invokeLater(new Runnable() { public void run() { LoginModel loginModel = new MyLoginModel(); LoginPresenter loginPresenter = new MyLoginPresenter(); loginPresenter.setModel(loginModel); LoginView loginView = new MyLoginView(); loginPresenter.setView(loginView); loginPresenter.setonLogin(new Runnable() { @Override public void run() { JOptionPane.showMessageDialog(null, "Welcome user!"); } }); loginPresenter.run(); } }); }}
