Question

关于java swing编程的问题

哪位高手能告诉下面那个我写的程序到底有什么问题啊，为什么不能显示出界面来啊
import java.net.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
class Client_graph extends JFrame implements ActionListener
{

JLabel LeaveMessage = new JLabel("留言",JLabel.CENTER);
JLabel MySay = new JLabel("我说:");
JButton ClearScreen = new JButton("清屏");
JButton SaveMessage = new JButton("保存");
JButton Retreat = new JButton("退出");
JButton SendMessage = new JButton("发送");
JTextField Message = new JTextField(20);
JTextArea ShowMessage = new JTextArea(40,40);
JPanel Panel1,Panel2,Panel3;
JScrollPane Panel4;

public Client_graph()
{
super("用户窗口");
Panel3.setLayout(new BorderLayout());
Panel3.add(ClearScreen,BorderLayout.NORTH);
Panel3.add(SaveMessage,BorderLayout.CENTER);
Panel3.add(Retreat,BorderLayout.SOUTH);
Panel4 = new JScrollPane(ShowMessage);
Panel1.setLayout(new FlowLayout());
Panel1.add(Panel4);
Panel1.add(Panel3);
Panel2.setLayout(new FlowLayout());
Panel2.add(MySay);
Panel2.add(Message);
Panel2.add(SendMessage);
setLayout(new BorderLayout());
add(LeaveMessage,BorderLayout.NORTH);
add(Panel1,BorderLayout.CENTER);
add(Panel2,BorderLayout.SOUTH);
setSize(600,800);
setLocation(550,200);
setVisible(true);

}

public void actionPerformed(ActionEvent e)
{

}

}
public class For_Client
{

public static void main(String args[])
{
new Client_graph();
}
}

Answer 1

程序有异常啊
Panel1 = new JPanel();
Panel2 = new JPanel();
Panel3 = new JPanel();
这几个面板没有创建对象就使用了，先创建对象 加载构造方法里面就行

还有创建JFrame 对象需要加上 窗口关闭处理，否则即使窗口关闭了，后台进程也是在运行着，占用着资源 构造方法里面加上这个个
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

即：构造方法如下：
public Client_graph()
{
super("用户窗口");

Panel1 = new JPanel();
Panel2 = new JPanel();
Panel3 = new JPanel();

Panel3.setLayout(new BorderLayout());
Panel3.add(ClearScreen,BorderLayout.NORTH);
Panel3.add(SaveMessage,BorderLayout.CENTER);
Panel3.add(Retreat,BorderLayout.SOUTH);
Panel4 = new JScrollPane(ShowMessage);
Panel1.setLayout(new FlowLayout());
Panel1.add(Panel4);
Panel1.add(Panel3);
Panel2.setLayout(new FlowLayout());
Panel2.add(MySay);
Panel2.add(Message);
Panel2.add(SendMessage);
setLayout(new BorderLayout());
add(LeaveMessage,BorderLayout.NORTH);
add(Panel1,BorderLayout.CENTER);
add(Panel2,BorderLayout.SOUTH);
setSize(600,800);
setLocation(550,200);
setVisible(true);

this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

}

Answer 2

没有建主页面，只是有一些控件，当然不会显示了