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本帖最后由 不会起名字的我 于 2021-8-20 12:24 编辑
Swing开发
仔细阅读下面这段代码,回答问题。
- import java.awt.event.ActionEvent;
- import java.awt.event.ActionListener;
- import javax.swing.*;
- public class Demo extends JFrame {
- private String username;
- private String pwd;
- private JButton login;
- private JTextField inputusername;
- private JPasswordField inputpwd;
- public Demo() {
- init();
- }
- void init() {
- setSize(500, 300);
- setDefaultCloseOperation(EXIT_ON_CLOSE);
- setTitle("Demo");
- JLabel l1 = new JLabel("用户名");
- JLabel l2 = new JLabel("密码");
- add(l1);
- add(getUsernameTextfield());
- add(l2);
- add(getPwdpasswordfield());
- add(getloginButton());
- }
- private JButton getloginButton() {
- login = new JButton("登录");
- login.setSize(30, 20);
- login.addActionListener(new ActionListener() {
- @Override
- public void actionPerformed(ActionEvent arg0) {
- if (getUsernameTextfield().getText() == username) {
- String password = String.valueOf(getPwdpasswordfield().getPassword());
- if (password == pwd) {
- JOptionPane.showMessageDialog(null, "登录成功!");
- } else {
- JOptionPane.showMessageDialog(null, "密码错误", "错误", JOptionPane.ERROR_MESSAGE);
- }
- } else {
- JOptionPane.showMessageDialog(null, "不存在的用户名", "错误", JOptionPane.ERROR_MESSAGE);
- }
- }
- });
- return login;
- }
- private JTextField getUsernameTextfield() {
- inputusername = new JTextField(10);
- return inputusername;
- }
- private JPasswordField getPwdpasswordfield() {
- inputpwd = new JPasswordField(10);
- inputpwd.setEchoChar('*');
- inputpwd.addActionListener(new ActionListener() {
- @Override
- public void actionPerformed(ActionEvent e) {
- login.doClick();
- }
- });
- return inputpwd;
- }
- public static void main(String[] args) {
- new Demo().setVisible(true);
- }
- }
复制代码
你知道为什么运行后整个窗体都是一个按钮吗?
答案
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