Hello World，Java Applet，问题

Question

I am having trouble with a HelloWorld Applet. 我在使用HelloWorld Applet时遇到麻烦。

Here is my Java code: 这是我的Java代码：

package webCrawler.applet2;

import javax.swing.JApplet;
import java.awt.Graphics;

public class HappyFace extends JApplet
{
    public void paint (Graphics canvas)
    {
        canvas.drawOval(100,50,200,200);
        canvas.fillOval(155,100,10,20);
        canvas.fillOval(230,100,10,20);
        canvas.drawArc(150,160,100,50,0,180);
    }
}

Here is my index.html : 这是我的index.html ：

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<html>
    <head>
    </head>
    <body bgcolor="000000">
        <center>
            <applet
                code    = "HappyFace.class"
                width   = "500"
                height  = "300"
                >
            </applet>
        </center>
    </body>
</html>

In Eclipse if I go: Run -> Run it works, however if I do this: 如果在Eclipse中，请执行以下命令： Run -> Run但可以，但是，如果这样做：

% pwd
/Users/me/Documents/workspace/WebCentric/bin/webCrawler/applet2
% ls
HappyFace.class         index.html
% open index.html

It opens the html page in Firefox but the app does not work: 它将在Firefox中打开html页面，但该应用程序无法运行：

应用程式无法运作

Update: 更新：

As Pablo Santa Cruz suggested I: 正如Pablo Santa Cruz所建议的那样：

Changed the location of index.html 更改了index.html的位置
Changed index.html to be code = "webCrawler.applet2.HappyFace" 将index.html更改为code = "webCrawler.applet2.HappyFace"

This is the exception in the console. 这是控制台中的例外。

java.lang.UnsupportedClassVersionError: webCrawler/applet2/HappyFace (Unsupported major.minor version 49.0)
    at java.lang.ClassLoader.defineClass0(Native Method)
    at java.lang.ClassLoader.defineClass(ClassLoader.java:539)
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:123)
    at sun.applet.AppletClassLoader.findClass(AppletClassLoader.java:213)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:289)
    at sun.applet.AppletClassLoader.loadClass(AppletClassLoader.java:151)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:235)
    at sun.applet.AppletClassLoader.loadCode(AppletClassLoader.java:680)
    at sun.applet.AppletPanel.createApplet(AppletPanel.java:635)
    at sun.plugin.AppletViewer.createApplet(AppletViewer.java:1991)
    at jep.AppletFramePanel.createApplet(Unknown Source)
    at sun.applet.AppletPanel.runLoader(AppletPanel.java:564)
    at sun.applet.AppletPanel.run(AppletPanel.java:301)
    at jep.AppletFramePanel.run(Unknown Source)
    at java.lang.Thread.run(Thread.java:552)

Answer 1

In your code attribute in the applet tag, you should use FQN of the class: webCrawler.applet2.HappyFace (remove .class extension also). 在applet标记的code属性中，应使用以下类的FQN： webCrawler.applet2.HappyFace （也请删除.class扩展名）。

Also, make sure you have your .class file inside the appropriate directory (package) structure. 另外，请确保您的.class文件位于适当的目录（包）结构内。 In your case, the HTML files should be in: 就您而言，HTML文件应位于：

/Users/me/Documents/workspace/WebCentric/bin/

And only your HappyFace.class file should be in: 并且只有HappyFace.class文件应该位于：

/Users/me/Documents/workspace/WebCentric/bin/webCrawler/applet2

Also, do keep in mind that there is a Java console on the Browser (IE, Firefox, Chrome, Safari) you can take a look at to see what's the error you are getting on applet execution. 另外，请记住，浏览器（IE，Firefox，Chrome，Safari）上有一个Java控制台，您可以查看一下执行applet时遇到的错误。

UPDATE: 更新：

Your Exception is saying that you compiled your code with a newer version of Java than the JVM supports. 您的例外是，您使用比JVM支持的Java版本更高的代码编译了代码。 IE you used Java 6 compiler in Eclipse but your Java Browser Plugin is only Java 5 (your JRE is only Java 5 ). 在IE中，您在Eclipse中使用了Java 6编译器，但您的Java Browser Plugin仅是Java 5 （您的JRE仅是Java 5 ）。

I would change project settings in Eclipse, tell it to use Java 5 compatible compiler (there is an option for that), compile and deploy the Applet again. 我将在Eclipse中更改项目设置，告诉它使用Java 5兼容的编译器（有一个选项），再次编译并部署Applet。 It should work. 它应该工作。

Hello World，Java Applet，问题

问题描述

1 个解决方案

解决方案1
2 已采纳 2010-10-03 14:32:19

Hello World，Java Applet，问题

问题描述

1 个解决方案

解决方案1 2 已采纳 2010-10-03 14:32:19

解决方案1
2 已采纳 2010-10-03 14:32:19