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java 窗体设置背景图片问题 (附上登陆界面代码，我想加个背景图片，求大神帮忙改改)

package com.qx;

import java.awt.Dimension;

import java.awt.GridLayout;

import java.awt.Toolkit;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import javax.swing.JButton;

import javax.swing.JFrame;

import javax.swing.JLabel;

import javax.swing.JOptionPane;

import javax.swing.JPanel;

import javax.swing.JTextField;

import javax.swing.*;

import java.awt.*;

public class ATMLoginFrame extends JFrame{

private JLabel **lCardNo,**lPasswd;

private JTextField jtfCardNo,jtfPasswd;

private JButton **Ok,**Cancel;

private JPanel jp1,jp2,jp3;

private Bank bank;

public ATMLoginFrame(){

bank=new Bank();

**lCardNo=new JLabel("用户名 :");

**lPasswd=new JLabel("密 码:");

jtfCardNo=new JTextField(20);

jtfPasswd=new JTextField(20);

**Ok=new JButton("确定 ");

**Cancel=new JButton("取消 ");

jp1=new JPanel();

jp2=new JPanel();

jp3=new JPanel();

jp1.add(**lCardNo);

jp1.add(jtfCardNo);

jp2.add(**lPasswd);

jp2.add(jtfPasswd);

jp3.add(**Ok);

jp3.add(**Cancel);

this.add(jp1);

this.add(jp2);

this.add(jp3);

this.setLayout(new GridLayout(4, 1));

Dimension d=Toolkit.getDefaultToolkit().getScreenSize();

this.setTitle(" ATM柜员机模拟程序 ");

this.setBounds((d.width-300)/2, (d.height-200)/2, 300, 200);

this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

this.pack();

this.setVisible(true);

this.setSize(700,500);

this.setResizable(false);

**Cancel.addActionListener(

new ActionListener(){

public void actionPerformed(ActionEvent e) {

dispose();

}

}

);

**Ok.addActionListener(

new ActionListener(){

public void actionPerformed(ActionEvent e) {

long cardNo=Integer.parseInt(jtfCardNo.getText());

String passwd=jtfPasswd.getText();

Account account=bank.verifyAccount(cardNo, passwd);

if(account!=null)

{

ATMMainFrame mainFrame=new ATMMainFrame(bank,account);

dispose();

}else{

JOptionPane.showMessageDialog(null, "卡号或密码错误 ", "信息提示 ",JOptionPane.ERROR_MESSAGE);

}

}

}

);

}

public static void main(String[] args) {

ATMLoginFrame atm=new ATMLoginFrame();

}

}

①窗体设置背景图片，②左上角的logo换成自己的图片，求大神帮我改一下，谢谢