bscountdown.java

一款即时通讯软件

package edu.ou.kmi.buddyspace.plugins.conference.gui;

/*
 * BSCountdown.java
 *
 * Project: BuddySpace
 * (C) Copyright Knowledge Media Institute 2002
 *
 *
 * Created on 29 October 2002, 8:43
 */

import java.util.*;
import javax.swing.*;
import java.awt.event.*;

import org.jabber.jabberbeans.util.*;

import edu.ou.kmi.buddyspace.plugins.conference.core.*;

/**
 * <code>BSCountdown</code> is the conference countdown, which automatically 
 * send coundown messages into conference room. It uses
 * <code>javax.swing.Timer</code>.
 *
 * @author  Jiri Komzak, Knowledge Media Institute, Open University, United Kingdom
 */
public class BSCountdown implements ActionListener {
    
    protected String name;
    protected int timeLeft;
    protected int curStep;
    protected javax.swing.Timer timer = null;
    protected Vector listeners = null;
    
    // thresholds in seconds for changing of countdown frequency
    public static int[] changeFreqTimes = {60, 30, 10, 5};
    // steps in seconds - must have changeFreqTimes.length+1 values
    public static int[] steps = {60, 30, 20, 5, 1};
    
    /**
     * Constructor.
     */
    public BSCountdown(String name, int minutes, int seconds) {
        this.name = name;
        this.timeLeft = minutes * 60 + seconds;
        listeners = new Vector();
        
        curStep = getNextStep();
        
        timer = new javax.swing.Timer(curStep * 1000, this);
        timer.setRepeats(false);
    }
    
    
    /** Returns length of next timer step */
    protected int getNextStep() {
        if (timeLeft <= 0) return 0;
        
        int curFreqIndex = 0;
        
        // finds the interval it's in
        for (int i=0; i < changeFreqTimes.length; i++)
            if (timeLeft <= changeFreqTimes[i])
                curFreqIndex = i+1;
        
        int step = steps[curFreqIndex];
        
        // aligns to whole steps
        int alignedTime = (timeLeft/step) * step;
        if (alignedTime != timeLeft)
            step = timeLeft - alignedTime;
        
        // aligns to the end of interval
        if (curFreqIndex < changeFreqTimes.length &&
            timeLeft - step < changeFreqTimes[curFreqIndex])
            step = timeLeft - changeFreqTimes[curFreqIndex];
        
        return step;
    }
    
    public void start() {
        timer.start();
    }
    
    public void stop() {
        timer.stop();
    }
    
    /** Returns time left */
    public int getTimeLeft() {
        return timeLeft;
    }
    
    public String getName() {
        return name;
    }
    
    public void actionPerformed(ActionEvent evt) {
        if (evt.getSource() == timer) {
            
            timeLeft = timeLeft - curStep;
            
            curStep = getNextStep();
            
            if (curStep != 0) {
                timer.setDelay(curStep*1000);
                timer.setInitialDelay(curStep*1000);
                timer.restart();
            }
            else {
                timer.removeActionListener(this);
            }
            
            fireActionPerformed(new ActionEvent(this, evt.getID(), 
                                evt.getActionCommand(), evt.getModifiers()));
        }
    }
    
    public void addActionListener(ActionListener listener) {
        if (listener == null) return;
        if (!listeners.contains(listener))
            listeners.add(listener);
    }
    
    public void removeActionListener(ActionListener listener) {
        if (listener == null) return;
        listeners.remove(listener);
    }
    
    protected void fireActionPerformed(ActionEvent e) {
        Enumeration ls = listeners.elements();
        while (ls.hasMoreElements()) {
            ActionListener l = (ActionListener) ls.nextElement();
            l.actionPerformed(new ActionEvent(this, e.getID(), e.getActionCommand()));
        }
    }
    
}