Moving an object such as an arc.

How would I go about programming an applet so that one could hit the arrow keys on the keyboard to make my arc (which is actually half a circle) move around on the applet screen?

You would add a KeyListener, which reacts to the keys you're interested in, then redraws the graphics as appropriate and calls repaint/update.

Since this has nothing to do with applets specifcially, I'm moving the thread to the AWT/Swing/GUI forum.
[ April 15, 2006: Message edited by: Ulf Dittmer ]

I'm new to this part of building an applet in java. Can somebody give me a reference or something that I could work with to figure it out? I'v never used a key refference before.

Event handling is discussed in a chapter of the Swing GUI tutorial. Even if you use AWT, not Swing, as your graphics library, the event handling of both is identical.

Heres my code:

import java.awt.*;
import java.applet.Applet;
 
/*
God Slime Volleyball
Created By: Martin vanPutten
Original Slime Volleyball Created By: Quin Pendragon (Fractoid) and Daniel Wedge (Wedgey)
*/
 
public class Slime extends Applet
 
{ // Slime Applet.

private Graphics g;
private int P;
private int C;
private int x;
private int y;
boolean Game = true;

public boolean KeyPressed (Event Initialize, int Key)
  
  { // Moves P.
    
    if (Game) 
    
    {
      
      if (Key == Event.LEFT)
          x = -1;
      if (Key == Event.RIGHT)
        x = 1;
      if (Key == Event.UP)
          y = -1;
      if (Key == Event.DOWN)
        y = 1;
 
}
 
} // End Moves P.
 
public void paint (Graphics g)

{ // Graphics.

setBackground (Color.red); // Background Color.

g.setColor (Color.black); // Ground.
g.fillRect (0, 500, 1000, 100);

g.setColor (Color.white); // Net.
g.fillRect (490, 440, 20, 60);

{ // Controller Slime.

g.setColor (Color.black); // Body.
g.fillArc (150, 440, 120, 120, 0, 180);

g.setColor (Color.yellow); // Eye
g.drawArc (220, 460, 35, 20, 40, 65);

} // End Controller Slime.

{ // Computer Slime.

g.setColor (Color.black); // Body.
g.fillArc (730, 440, 120, 120, 0, 180);

g.setColor (Color.yellow); // Eye
g.drawArc (725, 460, 70, 30, 65, 40);

} // End Computer Slime.

{ // Ball.

g.setColor (Color.blue); // Ball.
g.fillOval (195, 410, 30, 30);

} // End Ball.

} // End Graphics.

} // End Slime Applet.

I'm stuck here at trying to figure out how to give the first arc controls. Can somebody help me?

1) KeyPressed() is not keyListeners's keyPressed()
2) all the values in paint() are hard-coded i.e. there will be no 'movement'

here's a (very) simple applet, when run a 'ball' will move from left to right.
use the arrow keys to change direction

and the html to run it

Thanks! I can use this to figure mine out. Thank u so much!!

Ok... maybe I can't. I got this far:

import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;
 
/*
God Slime Volleyball
Created By: Martin vanPutten
Original Slime Volleyball Created By: Quin Pendragon (Fractoid) and Daniel Wedge (Wedgey)
*/
 
public class Slime extends Applet
 
{ // Slime Applet.

private Graphics g;
int x = 150;
int y = 440;
 
public void init ()

{

addKeyListener (new KeyAdapter ()

{
      
      public void keyPressed (KeyEvent ke)
      
      {
        
        if (ke.getKeyCode () == Event.LEFT)
        x =- 1;
        repaint ();
        
}

}
        
        );
  
}
 
public void paint (Graphics g)

{ // Graphics.

setBackground (Color.red); // Background Color.

g.setColor (Color.black); // Ground.
g.fillRect (0, 500, 1000, 100);

g.setColor (Color.white); // Net.
g.fillRect (490, 440, 20, 60);

g.setColor (Color.black); // Controller Slime Body.
g.fillArc (x, y, 120, 120, 0, 180);

/*

g.setColor (Color.yellow); // Controller Slime Eye.
g.drawArc (220, 460, 35, 20, 40, 65);

// Computer Slime.

g.setColor (Color.black); // Body.
g.fillArc (730, 440, 120, 120, 0, 180);

g.setColor (Color.yellow); // Eye.
g.drawArc (725, 460, 70, 30, 65, 40);

// End Computer Slime.

g.setColor (Color.blue); // Ball.
g.fillOval (195, 410, 30, 30);

*/

} // End Graphics.

} // End Slime Applet.

I commented all the unneccesary stuff away for now so that I can focus on the one arc. When I push a button (actually any button) on the keyboard, it looks like lines are going through the applet and its trying to do something but I'm not specific enough in my code to have it doing what I want it to do. For now... all I want is to move the arc left. If you want to view it the html code is:

What else do I have to do? Whats wrong with my applet?

here's your applet with a few comments

import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;
public class Slime extends Applet
{
  private Graphics g;//<------------why????
  int x = 150;
  int y = 440;
  public void init ()
  {
    addKeyListener (new KeyAdapter (){
      public void keyPressed (KeyEvent ke){
        if (ke.getKeyCode () == Event.LEFT)
        //from the docs:
        //NOTE: The Event class is obsolete and is available only for backwards compatilibility.
        // It has been replaced by the AWTEvent class and its subclasses
          x =- 1;//here you are setting x = 1, do you mean x -= 1?
          repaint ();//repaint on every keyPress - unless you want to block{} the if statement
        }});
  }
  public void paint (Graphics g)
  {
    setBackground (Color.red); // Background Color.//<---no need to setBackground on every repaint
    g.setColor (Color.black); // Ground.
    g.fillRect (0, 500, 1000, 100);//<-----------all you are doing is reducing the html 1000 x 600 to 1000 x 500
 
    g.setColor (Color.white); // Net.
    g.fillRect (490, 440, 20, 60);
 
    g.setColor (Color.black); // Controller Slime Body.
    g.fillArc (x, y, 120, 120, 0, 180);
  }
}

and here it is with a few amendments (will only work with the left arrow)