【新手提问】为什么我从别的类调过来的JPanel,显示的时候显示一下,就消失了呢?

[coolhty]

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.border.*;
import javax.swing.BorderFactory;

public class MainPage extends MouseAdapter{
	JFrame f;
	JPanel pnlleft;
	JPanel pnlright;
	JButton btninsert;
	JButton btnselects;
	JButton btndelete;
	JButton btnselectall;
	JButton btnamend;
	ImageIcon icon;
	Cursor hand;
	public MainPage(){
    	try{
			f.setDefaultLookAndFeelDecorated(true);
    	}catch(Exception e){
    		e.printStackTrace();
    	}
		f = new JFrame("学生管理系统");
		icon = new ImageIcon(".\\img\\lblbg1.gif");
		pnlleft = new JPanel();
		pnlright = new JPanel();
		btnselectall = new JButton(new ImageIcon(".\\img\\selectall.jpg"));
		btninsert = new JButton(new ImageIcon(".\\img\\insert.jpg"));
		btndelete = new JButton(new ImageIcon(".\\img\\delete.jpg"));
		btnamend = new JButton(new ImageIcon(".\\img\\amend.jpg"));
		btnselects = new JButton(new ImageIcon(".\\img\\selects.jpg"));
	//	f.setResizable(false);
	}
	public void action(){
		Toolkit tk=Toolkit.getDefaultToolkit();
		Image cursors=tk.getImage(".\\img\\mouse.gif");
		hand=tk.createCustomCursor(cursors,new Point(0,0),"cursor");
		f.setCursor(hand);
		setAttribute();
		f.setVisible(true);
		f.setLayout(null);
		f.setSize(new Dimension(500,400));
		pnlleft.setVisible(true);
		pnlleft.add(btnselectall);
		pnlleft.add(btninsert);
		pnlleft.add(btndelete);
		pnlleft.add(btnamend);
		pnlleft.add(btnselects);
		f.add(pnlleft);
		pnlleft.setOpaque(false);
		f.add(pnlright);
		f.addWindowListener(new WindowAdapter(){
			public void windowClosing(WindowEvent w){
				System.exit(0);
			}
			});
		btnselectall.addMouseListener(this);
		btninsert.addMouseListener(this);
		btndelete.addMouseListener(this);
		btnamend.addMouseListener(this);
		btnselects.addMouseListener(this);
	}
	public void setAttribute(){
		pnlleft.setLayout(null);
		pnlleft.setVisible(true);
		pnlleft.setBounds(new Rectangle(10,5,120,320));
		pnlleft.setBorder(BorderFactory.createTitledBorder("功能导航"));
		pnlright.setVisible(true);
		pnlright.setBounds(new Rectangle(140,5,340,320));
		pnlright.setBorder(BorderFactory.createTitledBorder("编辑区域"));
		btnselectall.setBounds(new Rectangle(15,25,90,40));
		btnselectall.setBorder(null);
		btninsert.setBounds(new Rectangle(15,90,90,40));
		btninsert.setBorder(null);
		btndelete.setBounds(new Rectangle(15,150,90,40));
		btndelete.setBorder(null);
		btnamend.setBounds(new Rectangle(15,210,90,40));
		btnamend.setBorder(null);
		btnselects.setBounds(new Rectangle(15,270,90,40));
		btnselects.setBorder(null);
	}
	public static void main(String[] args) {
		new MainPage().action();
		new Conn().close();
	}
	public void mouseEntered(MouseEvent m){
		f.setCursor(Cursor.HAND_CURSOR);
		if(m.getSource().equals(btnselectall)){
			btnselectall.setIcon(new ImageIcon(".\\img\\selectallout.jpg"));
		}else if(m.getSource().equals(btninsert)){
			btninsert.setIcon(new ImageIcon(".\\img\\insertout.jpg"));
		}else if(m.getSource().equals(btndelete)){
			btndelete.setIcon(new ImageIcon(".\\img\\deleteout.jpg"));
		}else if(m.getSource().equals(btnamend)){
			btnamend.setIcon(new ImageIcon(".\\img\\amendout.jpg"));
		}else if(m.getSource().equals(btnselects)){
			btnselects.setIcon(new ImageIcon(".\\img\\selectsout.jpg"));
		}
	}
	public void mouseExited(MouseEvent m){
		f.setCursor(hand);
		if(m.getSource().equals(btnselectall)){
			btnselectall.setIcon(new ImageIcon(".\\img\\selectall.jpg"));
		}else if(m.getSource().equals(btninsert)){
			btninsert.setIcon(new ImageIcon(".\\img\\insert.jpg"));
		}else if(m.getSource().equals(btndelete)){
			btndelete.setIcon(new ImageIcon(".\\img\\delete.jpg"));
		}else if(m.getSource().equals(btnamend)){
			btnamend.setIcon(new ImageIcon(".\\img\\amend.jpg"));
		}else if(m.getSource().equals(btnselects)){
			btnselects.setIcon(new ImageIcon(".\\img\\selects.jpg"));
		}
	}
	public void mousePressed(MouseEvent m){
		f.setCursor(Cursor.HAND_CURSOR);
		if(m.getSource().equals(btnselectall)){
			btnselectall.setIcon(new ImageIcon(".\\img\\selectallover.jpg"));
		}else if(m.getSource().equals(btninsert)){
			btninsert.setIcon(new ImageIcon(".\\img\\insertover.jpg"));
		}else if(m.getSource().equals(btndelete)){
			btndelete.setIcon(new ImageIcon(".\\img\\deleteover.jpg"));
		}else if(m.getSource().equals(btnamend)){
			btnamend.setIcon(new ImageIcon(".\\img\\amendover.jpg"));
		}else if(m.getSource().equals(btnselects)){
			btnselects.setIcon(new ImageIcon(".\\img\\selectsover.jpg"));
		}
	}
	public void mouseReleased(MouseEvent m){
		f.setCursor(Cursor.HAND_CURSOR);
		if(m.getSource().equals(btnselectall)){
			btnselectall.setIcon(new ImageIcon(".\\img\\selectall.jpg"));
		}else if(m.getSource().equals(btninsert)){
			btninsert.setIcon(new ImageIcon(".\\img\\insert.jpg"));
		}else if(m.getSource().equals(btndelete)){
			btndelete.setIcon(new ImageIcon(".\\img\\delete.jpg"));
		}else if(m.getSource().equals(btnamend)){
			btnamend.setIcon(new ImageIcon(".\\img\\amend.jpg"));
		}else if(m.getSource().equals(btnselects)){
			btnselects.setIcon(new ImageIcon(".\\img\\selects.jpg"));
		}
	}
	public void mouseClicked(MouseEvent m){
		if(m.getSource().equals(btnselectall)){
			Selectall all = new Selectall();
			pnlright.add(all.getJscrollpane());
			pnlright.setBorder(BorderFactory.createTitledBorder("所有学员"));
			f.setSize(new Dimension(660,400));
			pnlright.setSize(new Dimension(500,320));
		}else if(m.getSource().equals(btninsert)){//就是这里我调用的别的类的JPanel..
			Insert insert = new Insert();
			insert.action();
			f.setSize(new Dimension(500,410));
			pnlright.setSize(new Dimension(290,390));
			pnlright.add(insert.getpnl());
		}
	}
}

闪了一下就不见了..

麻烦前辈指点一下..谢谢.

[hunan0313]

f.setVisible(true);把这一行移到方法的最后面
public void action(){
Toolkit tk=Toolkit.getDefaultToolkit();
Image cursors=tk.getImage(".\\img\\mouse.gif");
hand=tk.createCustomCursor(cursors,new Point(0,0),"cursor");
f.setCursor(hand);
setAttribute();

f.setLayout(null);
f.setSize(new Dimension(500,400));
pnlleft.setVisible(true);
pnlleft.add(btnselectall);
pnlleft.add(btninsert);
pnlleft.add(btndelete);
pnlleft.add(btnamend);
pnlleft.add(btnselects);
f.add(pnlleft);
pnlleft.setOpaque(false);
f.add(pnlright);
f.addWindowListener(new WindowAdapter(){
public void windowClosing(WindowEvent w){
System.exit(0);
}
});
btnselectall.addMouseListener(this);
btninsert.addMouseListener(this);
btndelete.addMouseListener(this);
btnamend.addMouseListener(this);
btnselects.addMouseListener(this);
f.setVisible(true);
}