ballisticspanel.java

本书透彻讲解了经典的《设计模式：可复用面向对象软件的基础》一书涵盖的23种基本设计模式。本书将这些设计模式分成五类：接口型模式、责任型模式、构造型模式、操作型模式

package com.oozinoz.applications;

//import com.sun.java.swing.*;
import javax.swing.*;

//import java.util.*;
import java.awt.*;


import java.util.*;
import com.oozinoz.ballistics.*;

/*
* Copyright (c) 2001 Steven J. Metsker.
* 
* Steve Metsker makes no representations or warranties about
* the fitness of this software for any particular purpose, 
* including the implied warranty of merchantability.
*
* Please use this software as you wish with the sole
* restriction that you may not claim that you wrote it.
*/
/**
 * Plot a ballistics function. This class is refactored
 * from BallisticsPanel_2 to rely on a Tpeak object from
 * the business domain.
 * 
 * @author Steven J. Metsker
 */
public class BallisticsPanel
extends JPanel implements Observer 
{
protected void paintComponent(Graphics g)
{
	super.paintComponent(g); // paint the background
	for (int i = 0; i < nPoint; i++)
	{
		double t = ((double) i) / (nPoint - 1);
		x[i] = (int) (t * getWidth());
		y[i] =
			(int) (getHeight() * (1 - func.function(t, tPeak)));
	}
	g.drawPolyline(x, y, nPoint);
}

	protected BallisticsFunction func;
	protected int nPoint = 101;
	double tPeak = 0;
	protected int[] x = new int[nPoint];
	protected int[] y = new int[nPoint];





/**
 * Create a panel that can display the provided function.
 *
 * @param func the ballistics function to plot. Ballistics
 *             functions vary with time and with the time
 *             of peak burn area.
 * @param tPeak an observable model of the time when burn
 *              area peaks
 */
public BallisticsPanel(
	BallisticsFunction func,
	Tpeak tPeak)
{
	this.func = func;
	tPeak.addObserver(this);
}

/**
 * Respond to a change in the observed Tpeak model
 *
 * @param Observable presumably the model we are observing
 * @param arg ignored
 */
public void update(Observable o, Object arg)
{
	tPeak = ((Tpeak) o).getValue();
	repaint();
}
}