popup.java

Thinking in JAVA第四版源代码

//: gui/Popup.java
// Creating popup menus with Swing.
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import static net.mindview.util.SwingConsole.*;

public class Popup extends JFrame {
  private JPopupMenu popup = new JPopupMenu();
  private JTextField t = new JTextField(10);
  public Popup() {
    setLayout(new FlowLayout());
    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) {
    run(new Popup(), 300, 200);
  }
} ///:~