ballisticspanel.java

java设计模式源码

package app.observer.ballistics3;

/*
 * Copyright (c) 2001, 2005. 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.
 */

import javax.swing.*;

import com.oozinoz.ballistics.BallisticsFunction;

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

/**
 * 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 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();
    }

    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);
    }
}