Swing 设置无边框Frame

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

public class LogANA extends JFrame {

    //背景图片bgImage
    private ImageIcon bgImage = new ImageIcon("src/main/images/bg.jpg");
    //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;

    private ImageIcon bt1mage = new ImageIcon("src/main/images/mini.png");
    private ImageIcon bt1mage_enable = new ImageIcon("src/main/images/mini_enable.png");
    private ImageIcon bt2mage = new ImageIcon("src/main/images/close.png");
    private ImageIcon bt2mage_enable = new ImageIcon("src/main/images/close_enable.png");



    public LogANA() {

        getContentPane().setLayout(new BorderLayout());
        this.setLocationRelativeTo(null);
        this.setSize(bgImage.getIconWidth(), bgImage.getIconHeight());

        //处理拖动事件---去掉默认边框后，不能拖动了，具体实现如下
        this.addMouseListener(new MouseAdapter() {
            @Override
            public void mousePressed(MouseEvent e) {
                xOld = e.getX();//记录鼠标按下时的坐标
                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;
                LogANA.this.setLocation(xx, yy);//设置拖拽后，窗口的位置
            }
        });


        JPanel mainPanel = new JPanel();
        mainPanel.setBorder(BorderFactory.createLineBorder(Color.BLACK));
        mainPanel.setSize(bgImage.getIconWidth(), 100);
        mainPanel.setLayout(new FlowLayout(FlowLayout.RIGHT, 10, 10));

        //关闭按钮
        JButton miniBtn = new MyIconButton(bt1mage, bt1mage_enable, bt1mage, "");
        mainPanel.add(miniBtn);

        //关闭按钮
        JButton closeBtn = new MyIconButton(bt2mage, bt2mage_enable, bt2mage, "");
        mainPanel.add(closeBtn);


        getContentPane().add(mainPanel, BorderLayout.CENTER);

        closeBtn.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                System.exit(0);
            }
        });

        miniBtn.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                setExtendedState(JFrame.ICONIFIED);//最小化窗体
            }
        });

        setUndecorated(true);
        setLocationRelativeTo(null);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }

    public static void main(String[] args) {
        LogANA j = new LogANA();
        j.setVisible(true);
    }

}