java - JPanel.setSize() 不工作

Question

看看这段代码 friend 不知道为什么我不能设置JPanel的大小....

import java.io.*;
import java.util.*;
import java.sql.*;
//import java.applet.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
/*<applet code="k" height=400 width=400></applet>*/
public class k extends JApplet implements ActionListener
{
    JButton b,tinfo;
    JLabel l1,l2;
    JTextField f1,f2;
    JPanel p1;
    CardLayout c1;
    public void init()
    {
        b=new JButton("submit");

        f1=new JTextField(20);      
        f2=new JTextField(20);
        l1=new JLabel("username");
        l2=new JLabel("password");
        p1=new JPanel();
        c1=new CardLayout();
        add(l1);
        add(f1);
        add(l2);
        add(f2);
        add(b);
        add(p1);
        setLayout(new FlowLayout());
        b.addActionListener(this);

    }
    public void actionPerformed(ActionEvent ae)
    {
        //Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
        //Connection con=DriverManager.getConnection("jdbc:odbc:mohit:","system","rock");
        try
        {
            Properties p=new Properties();
            p.load(new FileInputStream("mohu.properties"));
            String str1=f1.getText();
            String str2=p.getProperty("username");
            System.out.println(str1);
            System.out.println(str2);
            //System.out.println(Integer.toString(str2.length()));
            if(str1.equals(str2))
            {
                if((f2.getText()).equals(p.getProperty("password")))
                {
                    System.out.println("you are entered");
                }
                else
                {
                    System.out.println("wrong first");
                }
            }
            else
            {
                System.out.println("wrong second ");
            }
            tinfo=new JButton("teachers information");
        p1.add(tinfo);
            p1.setSize(200,200);
            p1.setBackground(Color.RED);
            //tinfo.setSize(50,50);
            p1.setLayout(c1);
            c1.next(p1);
        }
        catch(Exception ee)
        {
            ee.printStackTrace();
            System.out.println("Exception caught ");
        }
    }

    public void paint()
    {}
}

Answer 1

尝试使用 p1.setPreferredSize(new Dimension(200,200))