JFrame中背景图大小随窗口大小自动改变

package com.ui; import java.awt.Color;import java.awt.Font;import java.awt.Graphics;import java.awt.Image; import javax.swing.ImageIcon;import javax.swing.JButton;import javax.swing.JLabel;import javax.swing.JPanel;import javax.swing.JPasswordField;import javax.swing.JTextField; public class MainTopPanel extends JPanel {private static final long serialVersionUID = -2783727170881461229L;private int width;private int height;private Image image = new ImageIcon(getClass().getClassLoader().getResource("com/resource/ZHU.jpg")).getImage();private JButton btnLogon = new JButton(" 登录 ");private JButton btnCancel = new JButton("  取消  ");private JLabel labId = new JLabel("账号：");private JLabel labPass = new JLabel("密码：");private JTextField fieldId = new JTextField();private JPasswordField fieldPass = new JPasswordField();private int btnLogon_x = 535, btnLogon_y = 399;private int btnCancel_x = 655, btnCancel_y = 399;private int labId_x = 495, labId_y = 339;private int labPass_x = 495, labPass_y = 369;private int fieldId_x = 545, fieldId_y = 339;private int fieldPass_x = 545, fieldPass_y = 369; public MainTopPanel(int width, int height) {this.width = width;this.height = height;this.setLayout(null);this.init();} public void setScreenSize(int width, int height) { //设置窗口变化后的大小this.width = width;this.height = height;} public void setLocationComponent(int width, int height) { //计算当窗口放大或者缩小，组件自动调整位置int m = this.width - width;int n = this.height - height;this.btnLogon_x -= m;this.btnLogon_y -= n;this.btnCancel_x -= m;this.btnCancel_y -= n;this.labId_x -= m;this.labId_y -= n;this.labPass_x -= m;this.labPass_y -= n;this.fieldId_x -= m;this.fieldId_y -= n;this.fieldPass_x -= m;this.fieldPass_y -= n;btnLogon.setBounds(this.btnLogon_x, this.btnLogon_y, 102, 22);btnCancel.setBounds(this.btnCancel_x, this.btnCancel_y, 102, 22);labId.setBounds(this.labId_x, this.labId_y, 57, 17);labPass.setBounds(this.labPass_x, this.labPass_y, 57, 17);fieldId.setBounds(this.fieldId_x, this.fieldId_y, 191, 22);fieldPass.setBounds(this.fieldPass_x, this.fieldPass_y, 191, 22);} private void init() {labId.setFont(new Font("微软雅黑", Font.PLAIN, 16));labId.setForeground(new Color(255, 255, 255));labId.setBounds(495, 339, 57, 17);labPass.setFont(new Font("微软雅黑", Font.PLAIN, 16));labPass.setForeground(new Color(255, 255, 255));labPass.setBounds(495, 369, 57, 17); btnLogon.setBounds(535, 399, 102, 22);btnLogon.setBackground(new Color(57, 149, 136));btnCancel.setBackground(new Color(57, 149, 136));btnCancel.setBounds(655, 399, 102, 22); fieldId.setBounds(545, 339, 191, 22);fieldId.setBackground(new Color(57, 149, 136));fieldId.setForeground(new Color(255, 255, 255));fieldPass.setBounds(545, 369, 191, 22);fieldPass.setBackground(new Color(57, 149, 136));fieldPass.setForeground(new Color(255, 255, 255)); this.add(labId);this.add(labPass);this.add(btnLogon);this.add(btnCancel);this.add(fieldId);this.add(fieldPass);} @Overrideprotected void paintComponent(Graphics g) {super.paintComponent(g);g.drawImage(image, 0, 0, width, height ,this);} }