Firing off events without user input

[zuber]

I was looking into making an RPG template for later use, and I stumbled (rather by accident ) upon what I thought was an interesting way to avoid the whole flickering screen problem. Essentially what I'm doing is writing the program as an applet with bits of JFrame in it:
(Note that this was edited slightly to be useable by people without my pictures)

code:

import java.awt.*; import java.awt.event.*; import javax.swing.*; public class MapTemplate extends JApplet     implements KeyListener, MouseListener {     static final int SQUARE_SIZE = 25;     Color squareColor;     int squareTop, squareLeft;     int xPos, yPos;     char[] [] state = new char [40] [21];     boolean focussed = false;     boolean[] keyPressed = new boolean [4];     DisplayPanel canvas;     //Image grass = Toolkit.getDefaultToolkit ().getImage ("grass.JPG");     //Image wall = Toolkit.getDefaultToolkit ().getImage ("wall.JPG");     public void init ()     {         //***************************************************************************************************         for (int j = 0 ; j < 40 ; j++)             for (int h = 0 ; h < 21 ; h++)                 state [j] [h] = 'e';         for (int j = 0 ; j < 10 ; j++)             state [20] [j] = 'f';         for (int j = 0 ; j < 10 ; j++)             state [j] [15] = 'f';         for (int k = 0 ; k < 3 ; k++)             // DL [k] = Toolkit.getDefaultToolkit ().getImage ("dl" + (k + 1) + ".jpg");             //***************************************************************************************************             squareTop = 0;         squareLeft = 0;         squareColor = Color.red;         canvas = new DisplayPanel ();         setContentPane (canvas);         canvas.setBackground (Color.white);         canvas.addKeyListener (this);         canvas.addMouseListener (this);         xPos = 0;         yPos = 0;     }     class DisplayPanel extends JPanel     {         //***************************************************************************************************         public void paintComponent (Graphics g)         {             super.paintComponent (g);             int width = getSize ().width;             int height = getSize ().height;             drawGrid (g);             g.setColor (squareColor);             g.fillRect (xPos * SQUARE_SIZE, yPos * SQUARE_SIZE, SQUARE_SIZE, SQUARE_SIZE);         }     }     //***************************************************************************************************     public void drawGrid (Graphics g)     {         for (int x = 0 ; x < 40 ; x++)             for (int y = 0 ; y < 20 ; y++)                 if (state [x] [y] != 'e')                 {                     g.setColor (Color.black);                     g.fillRect (x * 25, y * 25, 25, 25);                 }         //  g.drawImage (wall, x * 25, y * 25, this);         //  else         // g.drawImage (grass, x * 25, y * 25, this);         //  g.drawImage (DL [0], xPos * 25, yPos * 25, this);     }     //***************************************************************************************************     public void keyTyped (KeyEvent evt)     {         char ch = evt.getKeyChar (); // The character typed.         if (ch == 'B' || ch == 'b')         {             squareColor = Color.blue;             canvas.repaint ();         }         else if (ch == 'G' || ch == 'g')         {             squareColor = Color.green;             canvas.repaint ();         }         else if (ch == 'R' || ch == 'r')         {             squareColor = Color.red;             canvas.repaint ();         }         else if (ch == 'K' || ch == 'k')         {             squareColor = Color.black;             canvas.repaint ();         }     }     //***************************************************************************************************     public void keyPressed (KeyEvent evt)     {         int key = evt.getKeyCode (); // keyboard code for the key that was pressed         if (key == KeyEvent.VK_LEFT)         {             keyPressed [0] = true;         }         else if (key == KeyEvent.VK_RIGHT)         {             keyPressed [1] = true;         }         else if (key == KeyEvent.VK_UP)         {             keyPressed [2] = true;         }         else if (key == KeyEvent.VK_DOWN)         {             keyPressed [3] = true;         }         if (keyPressed [0] == true && xPos > 0 && state [xPos - 1] [yPos] == 'e')         {             xPos--;             canvas.repaint ();         }         else if (keyPressed [1] == true && xPos < 39 && state [xPos + 1] [yPos] == 'e')         {             xPos++;             canvas.repaint ();         }         if (keyPressed [2] == true && yPos > 0 && state [xPos] [yPos - 1] == 'e')         {             yPos--;             canvas.repaint ();         }         else if (keyPressed [3] == true && yPos < 19 && state [xPos] [yPos + 1] == 'e')         {             yPos++;             canvas.repaint ();         }     }     //***************************************************************************************************     public void keyReleased (KeyEvent evt)     {         int key = evt.getKeyCode ();         if (key == KeyEvent.VK_LEFT)         {             keyPressed [0] = false;         }         else if (key == KeyEvent.VK_RIGHT)         {             keyPressed [1] = false;         }         else if (key == KeyEvent.VK_UP)         {             keyPressed [2] = false;         }         else if (key == KeyEvent.VK_DOWN)         {             keyPressed [3] = false;         }     }     //***************************************************************************************************     public void mousePressed (MouseEvent evt)     {         canvas.requestFocus ();     }     public void mouseEntered (MouseEvent evt)     {     } // Required by the     public void mouseExited (MouseEvent evt)     {     } //    MouseListener     public void mouseReleased (MouseEvent evt)     {     } //       interface.     public void mouseClicked (MouseEvent evt)     {     } } // end class MapTemplate

Now thus far it all works fairly well, the collision/input/movement all work as intended. My problem is that if I want to put other things onto the screen I need to wait for user input, which is a pain. What I want to know is whether or not I can put in some code to fire off an event (which triggers the redrawing of the screen) without any sort of user input (So no keylistenner,mouselistener etc. and timers are impractical for what I'm trying to do, due to the ideally dynamic nature of the motion that will be on-screen).

So, can an event be fired without using a timer or human input?

[Reality Check]

Hey zuber we don't have to do an RPG anymore. He wants us to do something simpler. If you want to do the RPG for personal fulfillment go ahead but you know Cuyugan, you'll probably get 100 no matter what you hand in. But anyways, what Mike and I did was fire off dummy events through method calls that did nothing. I'm sure there are better ways to do it though.

[shadowman544]

i think that last post would be better suited for a pm rather than posting as an answer to a question

[zuber]

Forget a PM, he could have just told me yesterday in class, or today... in the same time it took him to tell me that he had responded to my topic =/
Assuming this works I guess I won't have to reach across the table to smack you

[Reality Check]

It's how I roll

[shadowman544]

lol ok

[Nick]

zuber @ Tue May 27, 2008 8:10 am wrote:

way to avoid the whole flickering screen problem.

Just double buffer

[shadowman544]

greesy I think you should explain that more

[Nick]

well the flickering occurs when indvidually drawing each object onto the screen, double buffering is basacally drawing everything off the screen, then moving it all onto the screen at once

[shadowman544]

thank you, a code example would have been nice bot thank you.
by your definition can we assume that this is like the view. update in turing.

[Hendo]

I do flicker free animation using offscreen graphics. Something like in your method where you draw everything have

code:

public void drawScene (Graphics g)     {         if (offScrImg == null)             offScrImg = createImage (size ().width, size ().height);         Graphics og = offScrImg.getGraphics ();         og.drawImage (mycoolpic, 0, 0, this);         og.drawImage (othercoolpic, 0, 0, this);         g.drawImage (offScrImg, 0, 0, this);     }

Just make sure to make a new image variable like so

code:

private Image offScrImg;