图18.9秒表Applet的运行效果
接下来就让我们看看Applet类的代码清单：
applets.StopWatchApplet package applets;
import java.applet.*; import java.awt.*;
import java.awt.event.*;
import javax.swing.ImageIcon; import javax.swing.JButton; /**
* 秒表Applet, 推荐大小200x200。
* 这个Applet展示了参数传递，多线程，图片加载，以及双缓冲技术 * @author BeanSoft * 日期：2008-05 */
public class StopWatchApplet extends Applet implements Runnable, ActionListener {
MediaTracker tracker;// 跟踪图象加载
Image pointImage, startImage, stopImage, resetImage;// 点图片, 开始图片, 停止图片,
Image[] digitals = new Image[10];// 数字0~9图片 Thread clockThread = null;// 主时钟线程
boolean stoped = false;// 秒表停止 int h, m, s, ds;// 时,分,秒,忽秒
// 下面的两个颜色
Color fg;// 背景色
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Color bg;// 前景色（文字颜色）
Panel southPanel = new Panel();//放在下部的面板 JButton resetButton;// 清零按钮
JButton controlButton;// 开始/停止 按钮
public void init() {
// 从参数中分析前景和背景色 try { } try { }
bg = Color.decode(getParameter(\)); bg = Color.black;
}catch(Exception e) {
fg = Color.decode(getParameter(\)); fg = Color.green; }catch(Exception e) {
// 设置布局管理器
setLayout(new BorderLayout());
tracker.addImage(pointImage, 0); for (int i = 0; i < 10; i++) { } try {
tracker.waitForAll();// 等待所有图片加载
digitals[i] = getImage(getDocumentBase(), \ + i + tracker.addImage(digitals[i], 0);
tracker = new MediaTracker(this);
pointImage = getImage(getDocumentBase(), \); startImage = getImage(getDocumentBase(), \); stopImage = getImage(getDocumentBase(), \); resetImage = getImage(getDocumentBase(), \); controlButton = new JButton(\停止\, new ImageIcon(stopImage)); resetButton = new JButton(\清零\, new ImageIcon(resetImage)); resetButton.setEnabled(false);
\);
jbInit();
validate();// 使按钮显示出来
clockThread = new Thread(this);
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clockThread.start();
} catch (Exception e) {
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e.printStackTrace();
// 覆盖以防止闪烁
public void update(Graphics g) {
}
}
paint(g); }
// 主要画图代码,双缓冲技术
public void paint(Graphics g) {
int width = getSize().width;// 窗口宽度 int height = getSize().height;// 窗口高度 int x = 10, y = 0;// X偏移,Y偏移
int imageWidth, imageHeight;// 图片宽度和高度
Image offImage = createImage(width, height);// 缓冲图 Graphics offG = offImage.getGraphics();// 缓冲图图画对象 // 设置背景色，填充图案
offG.setColor(bg);
offG.fillRect(0, 0, width, height);
// 设置前景色
offG.setColor(fg);
// 检查是否加载了所有图片
if (!tracker.checkAll()) {
offG.drawString(\正在加载图片,请稍候...\, 0, height / 2); } else {
// 画出当前时间 imageWidth = digitals[0].getWidth(this); imageHeight = digitals[0].getHeight(this);
offG.drawImage(digitals[(int) Math.floor(h / 10)], x, y, this);
offG.drawImage(digitals[h % 10], x + imageWidth * 1, y, this); offG.drawImage(pointImage, x + imageWidth * 2, y, this); offG.drawImage(digitals[(int) Math.floor(m / 10)], x + imageWidth
* 3, y, this);
offG.drawImage(digitals[m % 10], x + imageWidth * 4, y, this); offG.drawImage(pointImage, x + imageWidth * 5, y, this); offG.drawImage(digitals[(int) Math.floor(s / 10)], x + imageWidth
* 6, y, this);
offG.drawImage(digitals[s % 10], x + imageWidth * 7, y, this);
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offG.drawImage(pointImage, x + imageWidth * 8, y, this); offG.drawImage(digitals[ds], x + imageWidth * 9, y, this); String str = \;
if (stoped)
str = \停止\; else
str = \计时\;
offG.drawString(\秒表 - \ + str, x, y + imageHeight * 2); String ss;
if (s < 10)
ss = \ + s;// 格式化为 \ else
ss = \ + s; String sm;
if (m < 10)
sm = \ + m;// 格式化为 \ else
sm = \ + m;
offG.setFont(new Font(\, Font.BOLD, imageHeight)); offG.drawString(h + \ + sm + \ + ss + \ + ds, x, y + imageHeight * 3);
}
// 显示缓冲图
g.drawImage(offImage, 0, 0, this); }
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// 按钮事件
public void actionPerformed(ActionEvent e) {
Object source = e.getSource(); if (source == controlButton) {
stoped = !stoped; if (stoped) { }
controlButton.setText(\开始\);
controlButton.setIcon(new ImageIcon(startImage)); resetButton.setEnabled(true); clockThread = null;
controlButton.setText(\停止\);
controlButton.setIcon(new ImageIcon(stopImage)); clockThread = new Thread(this); clockThread.start();
resetButton.setEnabled(false);
} else {
} else if (source == resetButton) {
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}
if (stoped) { }
h = m = s = ds = 0;
resetButton.setEnabled(false);
repaint(); } 间
if (++ds == 10)// 1秒 { } try {
ds = 0;
if (++s == 60)// 1分 { }
s = 0;
if (++m == 60)// 1小时 { }
m = 0; ++h;
// 线程代码
public void run() {
while (Thread.currentThread() == clockThread) {
long startTime = System.currentTimeMillis();// 记住线程开始时
repaint();
startTime += 100;
Thread.sleep(Math.max(0, startTime - System.currentTimeMillis()));
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}
// 确保睡眠100毫秒
} catch (InterruptedException ie) { }
}
// 构造界面
private void jbInit() throws Exception {
southPanel.setBackground(SystemColor.control); resetButton.addActionListener(this); controlButton.addActionListener(this); this.setBackground(Color.black);
this.add(southPanel, BorderLayout.SOUTH);
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