jpopupmenu行为

我在下面准备了一个小测试用例。我的问题是右键单击窗口。jpopupmenu会出现,但如果我单击jWindow菜单以外的任何地方,它不会消失。我必须点击窗口上的某个地方来摆脱它,这不是预期的行为。

编辑: 在阅读完AKF的答案后,我切换到JFrame,当帧处于焦点并且弹出菜单显示它在你点击另一个窗口时消失。但是,如果窗口没有焦点,并且您单击某处菜单不会消失。

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

class test {

    static class window extends JWindow
    implements MouseListener, MouseMotionListener{

    JPopupMenu popMenu;
    JPanel panel = new JPanel();

    Point location;
    MouseEvent pressed;

    public window(){

        addMouseListener( this );
        addMouseMotionListener( this );

        JLabel label = new JLabel("JWindow", JLabel.CENTER);

        initPopMenu();
        add(label);
        setVisible(true);
        setAlwaysOnTop(true);
        setLocationRelativeTo(null);
        pack();
    }

    public void initPopMenu(){
        popMenu = new JPopupMenu();
        JMenuItem item;

        item = new JMenuItem( "Title" );
        item.setEnabled(false);
        popMenu.add(item);
        popMenu.addSeparator();

        item = new JMenuItem( "Item One" );
        popMenu.add(item);

        item = new JMenuItem( "Item 2" );
        popMenu.add(item);

        item = new JMenuItem( "Item 3" );
        popMenu.add(item);
    }

    public void mousePressed(MouseEvent e)
    {
        pressed = e;
        int nModifier = e.getModifiers();
        if (((nModifier & InputEvent.BUTTON2_MASK) != 0)||
        ((nModifier & InputEvent.BUTTON3_MASK) != 0))
        popMenu.show( this, e.getX(), e.getY() );
    }

    public void mouseClicked(MouseEvent e) {
    }


    public void mouseReleased(MouseEvent e) {}

    public void mouseDragged(MouseEvent me){
    }

    public void mouseMoved(MouseEvent e) {}
    public void mouseEntered(MouseEvent e) {}
    public void mouseExited(MouseEvent e) {}
    }
    public static void main(String[] args) {
    window dw = new window();
    }
}