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Applets

First time with applets

Greenhorn

Posts: 19

posted 15 years ago

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I'm having a bit of trouble getting my applet to appear. I am using bravenet.com for my webhost and have uploaded the file using the file manager. My code for the applet is this

import java.applet.*;
import java.awt.*;
import javax.swing.*;
import java.awt.geom.*;
import java.util.ArrayList;
import java.util.Random;

public class BallRoom extends JApplet
{
    private final int WIDTH = 350;
    private final int HEIGHT = 300;
    private PaintSurface canvas;

public void init()
    {
        this.setSize(WIDTH,HEIGHT);
        canvas = new PaintSurface();
        this.add(canvas, BorderLayout.CENTER);
        Thread t = new AnimationThread(this);
        t.start();
    }
}

class AnimationThread extends Thread
{
    JApplet c;
    
    public AnimationThread(JApplet c)
    {
        this.c = c;
    }
    
    public void run()
    {
        while(true)
        {
            c.repaint();
            try
            {
                Thread.sleep(20);
            }
            catch (InterruptedException ex)
            {
                
            }
        }
    }
}

class PaintSurface extends JComponent
{
    public ArrayList<Ball> balls = new ArrayList<Ball>();
    
    public PaintSurface()
    {
        for (int i = 0; i < 20; i++)
            balls.add(new Ball(20));
    }
    
    public void paint(Graphics g)
    {
        Graphics2D g2 = (Graphics2D)g;
        g2.setRenderingHint(
            RenderingHints.KEY_ANTIALIASING,
            RenderingHints.VALUE_ANTIALIAS_ON);
        g2.setColor(Color.RED);
        for (Ball ball : balls)
        {
            ball.move();
            g2.fill(ball);
        }
    }
}

class Ball extends Ellipse2D.Float
{
    private int x_speed,y_speed,d;
    private int width = 350;
    private int height = 300;
    
    public Ball(int diameter)
    {
        super(((int)(Math.random() * (width - 20) + 1)),((int)(Math.random() * (height - 20) + 1)),diameter,diameter);
        this.d = diameter;
        this.x_speed = (int)(Math.random() * 5 + 1);
        this.y_speed = (int)(Math.random() * 5 + 1);
    }
    
    public void move()
    {
        if (super.x < 0 || super.x > width - d)
            x_speed = -x_speed;
        if (super.y < 0 || super.y > height - d)
            y_speed = -y_speed;
        super.x += x_speed;
        super.y += y_speed;
    }
}

And my code for my website is this

When I open up the page it says "Error. Click for details"

Ulf Dittmer

Rancher

Posts: 43081

posted 15 years ago

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The CODE attribute takes just the class name, which is "BallRoom" or "BallRoom.class". If the class files are not in the same directory as the HTML file, then you need to use a CODEBASE attribute to point to it; in this case it would have a value of "java". The AppletsFaq points to a tutorial on all the details of the APPLET tag.

As an aside, there's no point in calling setSize in an applet - it takes its size from the HEIGHT and WIDTH attributes of the applet tag, and can't be resized.

Lastly, whenever you have problems with applets, check for error messages in the Java Console - that's where any exceptions will be logged, and it's where any System.out messages written by code would show up.

P Mc Gartoll

Greenhorn

Posts: 19

posted 15 years ago

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I checked the java console and it didn't say anything other than the version of java I had. I figured out how to solve the problem by using the files URL.

Ulf Dittmer

Rancher

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posted 15 years ago

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Do you mean an URL that starts with "file:///"? If so, that works on your local machine only - not on an actual host.

P Mc Gartoll

Greenhorn

Posts: 19

posted 15 years ago

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Here is my HTML code but it doesn't work. It is still somehow finding the files on my computer because when I open it up on any other computer it doesn't work.

I got the codebase idea from the java tutorials but it doesn't work. Any help?
If you type in
http://drenguin.bravehost.com/Applet.class
then it shows you the class.

P Mc Gartoll

Greenhorn

Posts: 19

posted 15 years ago

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Also, the applet runs on my computer even when the file is not on the server so I know it is somehow getting it from the computer.

Ulf Dittmer

Rancher

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posted 15 years ago

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If you type in
http://drenguin.bravehost.com/Applet.class
then it shows you the class.

Actually, I'm getting some kind of "page not found" message for that URL.

P Mc Gartoll

Greenhorn

Posts: 19

posted 15 years ago

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Sorry I removed the file for a little bit to see if the applet would run without the file, it should work now if you click on the link!

Ulf Dittmer

Rancher

Posts: 43081

posted 15 years ago

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It seems that should work; what exactly happens if you try it - is there an exception in the Java Console? Be sure to set Java 6 as the JRE, since that's what the applet is compiled for.

P Mc Gartoll

Greenhorn

Posts: 19

posted 14 years ago

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How does one set a JRE?

Ulf Dittmer

Rancher

Posts: 43081

posted 14 years ago

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Using the Java Plugin control panel on Windows, or using /Applications/Utilities/Java Preferences.app on OS X.

P Mc Gartoll

Greenhorn

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posted 14 years ago

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I used the Java Preferences thingy and it was already on 6.
I am assuming that you have Java 6 also so could you tell me if this site has an ok button, that is my applet. Pardon the ads but I'm using one of those free website things right now.

http://drenguin.bravehost.com/Applet.htm

Ulf Dittmer

Rancher

Posts: 43081

posted 14 years ago

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Actually, I don't use Java 6. After setting Java 6 as the default JRE in the Java Preferences.app neither Safari nor Firefox are able to run any applets, so I'm not sure what's going on with yours.

P Mc Gartoll

Greenhorn

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posted 14 years ago

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The applet works on my computer. On other computers they now get the java loading sign (the cup with the arrows around it)

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