Posted on 2007-03-17 10:48
tanzek 阅读(3203)
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还是在看Java Tutorial，到了"Applets"。
下面就列出一些看到的重点吧。
An applet is a special kind of Java program that a browser enabled with Java technology can download from the internet and run. An applet is typically embedded inside a web
-
page and runs in the context of the browser. An applet must be a subclass of the java.applet.Applet
class
, which provides the standard
interface
between the applet and the browser environment.
applet是一种特殊的JAVA程序，允许带有Java技术的浏览器能够从Internet下载它并运行。applet是典型的嵌入到网页里面并在浏览器上下文中运行的。applet必须是java.applet.Applet类的子类，java.applet.Applet提供applet和浏览器环境之间的接口标准。
Swing provides a special subclass of Applet, called javax.swing.JApplet, which should be used
for
all applets that use Swing components to construct their GUIs.
Swing提供一个特殊的applet子类，叫做javax.swing.JApplet，当所有的applet要用到Swing部件来构造他们的GUI时，那么它就需要用到它。
By calling certain methods, a browser manages an applet life cycle,
i
f
an applet is loaded in a web page.
如果applet已经加载到一个网页中，那么通过调用applet的某一方法，浏览器可以控制applet的生命周期。
上面讲了applet的一些知识，接下来的就是applet的生命周期的讲解了：
方法地地Life Cycle of an Applet: Basically, there are four methods in the Applet class on which any applet is built.
Applet的生命周期：基本上，在Applet类的每个实例中有四个方法。
init: This method is intended for whatever initialization is needed for your applet. It is called after the param attributes of the applet tag.
init：这个往往用来执行你的applet需要做的所有初始化工作，当在applet标记中的param属性读入后开始调用。
start: This method is automatically called after init method. It is also called whenever user returns to the page containing the applet after visiting other pages.
start：此方法在init方法调用完后自动调用，它是执行访问其它页面后用户重新返回到包含applet的页面中时的操作。
stop: This method is automatically called whenever the user moves away from the page containing applets. You can use this method to stop an animation.
stop：此方法当用户从包含applet的页面中离开时自动调用，你能够用此方法来停止你的动画。
destroy: This method is only called when the browser shuts down normally.
destroy：此方法仅当正常地关闭浏览器时被调用。
Thus, the applet can be initialized once and only once, started and stopped one or more times in its life, and destroyed once and only once.
因此，applet仅能用init一次，能够在它的生命中被start和stop一次或多次，同时也仅能被destroy一次。
最后还用一个例子吧：
1
/**//*
2
* Java(TM) SE 6 Version
3
*/
4
5import java.applet.Applet;
6import java.awt.Graphics;
7
8//No need to extend JApplet, since we don't add any components;
9//we just paint.
10public class Simple extends Applet 
{
11
12 StringBuffer buffer;
13
14
public void init() {
15 buffer = new StringBuffer();
16 addItem("initializing ");
17
}
18
19 public void start() {
20 addItem("starting ");
21 }
22
23 public void stop() {
24 addItem("stopping ");
25 }
26
27 public void destroy() {
28 addItem("preparing for unloading");
29 }
30
31 private void addItem(String newWord) {
32 System.out.println(newWord);
33 buffer.append(newWord);
34 repaint();
35 }
36
37 public void paint(Graphics g) {
38 //Draw a Rectangle around the applet's display area.
39 g.drawRect(0, 0,
40 getWidth() - 1,
41 getHeight() - 1);
42
43 //Draw the current string inside the rectangle.
44 g.drawString(buffer.toString(), 5, 15);
45 }
46}