这个程序中，弹出的框，没有内容是怎么回事

Question

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

public class Login extends JFrame {

 /** * */

 private static final long serialVersionUID = 1L;

 JLabel a1 = new JLabel("账号：");

 JLabel a2 = new JLabel("密码：");

 JButton b1 = new JButton("确定");

 JButton b2 = new JButton("重置");

 JTextField jt;

 JPasswordField jp;

 public Login() {

  setTitle("登录");

  setBounds(500, 250, 300, 200);

  setVisible(true);

  setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);

  Container cp = getContentPane();

   jt = new JTextField(15);

   jp = new JPasswordField(15);

  JPanel p1 = new JPanel();

  p1.add(a1);

  p1.add(jt);

  

  JPanel p2 = new JPanel();

  p2.add(a2);

  p2.add(jp);

  

  JPanel p3 = new JPanel();

  p3.add(b1);

  p3.add(b2);

  

  cp.add( p1,BorderLayout.NORTH);

  cp.add(p2,BorderLayout.CENTER);

  cp.add( p3,BorderLayout.SOUTH);

  

  b2.addActionListener(new ActionListener() {

   public void actionPerformed(ActionEvent arge0) {

    jt.setText("");

    jp.setText("");

   }

  });

  b1.addActionListener(new ActionListener() {

   public void actionPerformed(ActionEvent arg0) {

    String t1 = jt.getText();

    String jt1 = "test1";

    if ((t1.trim().equals(jt1))

      && new String(jp.getPassword()).trim().equals("test1")) {

     JOptionPane.showMessageDialog(null, "登录成功");

    } else {

     JOptionPane.showMessageDialog(null, "用户或密码错误，请重新输入");

    }

   }

  });

 }

 

 publi

c static void main(String[] args) {

  new Login();

 }

}

 

Answer 1

因为你没给组件设置大小，所以显示不了。