java弹出式菜单

JPopupMenu的执行看起来有一些别扭：我们必需挪用enableEvents()要领并选择鼠标事件取代操作事件吸收器。它大概增加一个鼠标吸收器但MouseEvent从isPopupTrigger()处不会返回真值——它不知道将激活一个弹出菜单。别的，当我们实验吸收器要领时，它的行为令人不行思议，这或者是鼠标单击勾当引起的。在下面的措施例子里一些事件发生了这种弹出行为：
 

//: Popup.java
// Creating popup menus with Swing
package c13.swing;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class Popup extends JPanel {
  JPopupMenu popup = new JPopupMenu();
  JTextField t = new JTextField(10);
  public Popup() {
    add(t);
    ActionListener al = new ActionListener() {
      public void actionPerformed(ActionEvent e){
        t.setText(
          ((JMenuItem)e.getSource()).getText());
      }
    };
    JMenuItem m = new JMenuItem("Hither");
    m.addActionListener(al);
    popup.add(m);
    m = new JMenuItem("Yon");
    m.addActionListener(al);
    popup.add(m);
    m = new JMenuItem("Afar");
    m.addActionListener(al);
    popup.add(m);
    popup.addSeparator();
    m = new JMenuItem("Stay Here");
    m.addActionListener(al);
    popup.add(m);
    PopupListener pl = new PopupListener();
    addMouseListener(pl);
    t.addMouseListener(pl);
  }
  class PopupListener extends MouseAdapter {
    public void mousePressed(MouseEvent e) {
      maybeShowPopup(e);
    }
    public void mouseReleased(MouseEvent e) {
      maybeShowPopup(e);
    }
    private void maybeShowPopup(MouseEvent e) {
      if(e.isPopupTrigger()) {
        popup.show(
          e.getComponent(), e.getX(), e.getY());
      }
    }
  }
  public static void main(String args[]) {
    Show.inFrame(new Popup(),200,150);
  }
} ///:~

沟通的ActionListener被插手每个JMenuItem中，使其能从菜单标签中取出文字，并将文字插入JTextField。