介绍:细处着手,巧处用功。高手和菜鸟之间的差别就是:高手什么都知道,菜鸟知道一些。电脑小技巧收集最新奇招高招,让你轻松踏上高手之路。(首月免费) Applet是在浏览器中运行的小程序,Java也是从Applet开始风靡世界的。通过编写这个Applet,我们可以学习到如下知识:
1. Applet及JApplet中的主要接口
2. 图像的装载及MediaTracker的使用
3. 线程的使用及多个线程直接的通讯
4. Thread.join()方法的使用
5. volatile关键字的使用
首先看看运行效果:点击运行
动画的主要部分是一个Applet,从codebase中读取一组图片文件,然后每隔1秒轮换显示一张。代码如下:
import javax.swing.JApplet; import java.awt.Graphics; import java.awt.Image; import java.awt.MediaTracker; public class Animate extends JApplet { //图片数量 private static final int NUM_OF_PIC = 4; int count; Image pics[]; TimerThread timer; public void init() { count = 1; pics = new Image[NUM_OF_PIC]; MediaTracker tracker = new MediaTracker(this); for(int i = 0; i<NUM_OF_PIC; i++) { //将图片按照0,1,...,NUM_OF_PIC -1,放置在目录中,格式为.jpg pics[i] = getImage(getCodeBase(), new Integer(i).toString()+".jpg"); tracker.addImage(pics[i], 0); } tracker.checkAll(true); } public void start() { timer = new TimerThread(this, 1000); timer.start(); } public void stop() { timer.shouldRun = false; try { timer.join(); //等待timer线程退出 } catch (InterruptedException e){}; } public void paint(Graphics g) { g.drawImage(pics[count++], 0, 0, null); if(count == NUM_OF_PIC) count = 0; } }
动画的控制由一个专门的线程TimerThread进行处理,
import java.awt.Component; public class TimerThread extends Thread { Component comp; int timediff; // shouldRun声明为volatile volatile boolean shouldRun; public TimerThread(Component comp, int timediff) { super("TimerThread(" + timediff + " millseconds"); this.comp = comp; this.timediff = timediff; shouldRun = true; } public void run() { while(shouldRun) { try { comp.repaint(); sleep(timediff); } catch (Exception e){} } } }
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