Java中JFrame实现无边框无标题方法

package com.qiantu.jframe;import java.awt.event.ActionEvent;import java.awt.event.ActionListener;import java.awt.event.MouseAdapter;import java.awt.event.MouseEvent;import java.awt.event.MouseMotionAdapter;import javax.swing.ImageIcon;import javax.swing.JButton;import javax.swing.JFrame;import javax.swing.JLabel;import javax.swing.JLayeredPane;import javax.swing.JPanel;public class JFrameNoBorder extends JFrame {  public static void main(String[] args) { JFrameNoBorder j = new JFrameNoBorder(); j.setVisible(true); }  private static final long serialVersionUID = 1L; //用于处理拖动事件，表示鼠标按下时的坐标，相对于JFrame int xOld = 0; int yOld = 0;  public JFrameNoBorder() { this.setLayout(null); //处理拖动事件 this.addMouseListener(new MouseAdapter() {  @Override  public void mousePressed(MouseEvent e) {  xOld = e.getX();  yOld = e.getY();  } }); this.addMouseMotionListener(new MouseMotionAdapter() {  @Override  public void mouseDragged(MouseEvent e) {  int xOnScreen = e.getXOnScreen();  int yOnScreen = e.getYOnScreen();  int xx = xOnScreen - xOld;  int yy = yOnScreen - yOld;  JFrameNoBorder.this.setLocation(xx, yy);  } }); //JLayeredPane用于添加两个图层的，一个用于背景，一个用于界面 JLayeredPane layeredPane = new JLayeredPane(); layeredPane.setBounds(0, 0, 200, 200); this.add(layeredPane);  //背景Panel JPanel bgPanel = new JPanel(); bgPanel.setBounds(0, 0, 200, 200); layeredPane.add(bgPanel);  //背景图片，添加到背景Panel里面 JLabel bgLabel = new JLabel(new ImageIcon("img/bgImage.png")); bgPanel.add(bgLabel);  //主界面，也就是背景上面的一层Panel JPanel mainPanel = new JPanel(); mainPanel.setBounds(0, 0, 200, 200); mainPanel.setLayout(null); layeredPane.add(mainPanel); //关闭按钮 JButton closeButton = new JButton(); closeButton.setIcon(new ImageIcon("img/closeButton.png")); closeButton.setBounds(170, 0, 30, 30); closeButton.addActionListener(new ActionListener() {  @Override  public void actionPerformed(ActionEvent e) {  System.exit(0);  } }); mainPanel.add(closeButton);  this.setBounds(50,50,200,200); this.setUndecorated(true); }}