itsukyuquotation.java

java模式之命令模式的一个具体应用

/**
 * 视窗类上的Panel类的源代码，
 * 它同时实现了AWT的事件监听接口ActionListener
 */

package itsukyu;

import java.awt.BorderLayout;
import java.awt.Panel;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
 
@SuppressWarnings("serial")
class ItsukyuQuotation extends Panel implements ActionListener
{
    /**
     * @link aggregation 
     */
    private final Command undo ;
 
    /**
     * @link aggregation 
     */
    private final Command redo ;
 
    // Constructor
    public ItsukyuQuotation(UndoableTextArea text)
    {
 
        setLayout(new BorderLayout());
 
        // create a toolbar for buttons
        Panel toolbar = new Panel();
 
        // create undo and redo buttons
        // add listeners for buttons
        undo = new UndoCommand(text);
        redo = new RedoCommand(text);
 
        undo.addActionListener (this);
        
        redo.addActionListener (this);
 
        // add buttons to toolbar
        toolbar.add(undo);
        toolbar.add(redo);
 
        // add toolbar and text area to panel
        add(toolbar, "North");
        add(text, "Center");
    }
      //-----------------------------------------
     public void actionPerformed(ActionEvent e)
     {
         Command cmd = (Command)e.getSource();
         cmd.execute();
     }
 
}