Computer Science Canada

Java and Graphics... update screen...
Author:  Homer_simpson [ Tue Feb 17, 2004 5:45 pm ]
Post subject:  Java and Graphics... update screen...
let's say i gots this:

code:
import java.io.*;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.math.*;

class gui
{
    public static void main (String args [])
    {
        JFrame frame = new JFrame ("Someshit");
        frame.addWindowListener (new WindowAdapter ()
        {
            public void windowClosing (WindowEvent e)
            {
                System.exit (0);
            }
        }
        );
        frame.setSize (600, 400);
        JPanel pane = (JPanel) frame.getContentPane ();
        pane.add (new SysDraw ());
        frame.setVisible (true);
    }
}


class SysDraw extends JComponent
{
    public SysDraw ()
    {
        repaint ();

    }


    public void paint (Graphics g)
    {
      for (int i=0;i<600;i++)
      {
        g.drawLine(0,0,i,400);
      }
    }
}





got my gui window setup and everything but when i draw stuffs on the page... in this case a line...it doesn't update the screen so i can delete that and draw again... now i'm wondering if there is a command like View.Update in turing for java?
Author:  Homer_simpson [ Wed Feb 18, 2004 10:52 am ]
Post subject: 
basically all i need is an equivalent for View.Update for java! Confused
Author:  Dan [ Wed Feb 18, 2004 11:29 am ]
Post subject: 
i know there is one in the java 2d api, i will check when i get home on how to use it....
Author:  Homer_simpson [ Wed Feb 18, 2004 5:33 pm ]
Post subject: 
awesome!
Author:  rizzix [ Fri Feb 20, 2004 5:55 pm ]
Post subject: 
extending my previous example.. (once again)

Java:
import javax.swing.*;
import java.awt.*;

class DrawView extends Canvas {
   
    private Image bImage;     // offscreen buffer
    private Graphics bg;      // offscreen graphics context
    private Graphics2D g2d;   // onscreen graphics context
    private int w, h;         // width and height of canvas (Component)
   
    DrawView(int width, int height) {
        super();
        setBackground(Color.black);
        w = width;
        h = height;
    }
   
    public void paint(Graphics g) {
        g2d    = (Graphics2D) g;         // cast to Graphics2D (just in case)
        bImage = createImage(w, h);      // create a new buffer image
        bg     = bImage.getGraphics();   // get Graphics context for image
       
        bg.setXORMode(Color.white);      // set white as the XORed colour
       
        for (int i = 0; i < 600; i++)
        {
            bg.drawLine(0,0,i,400);     // drawn in white (on buffer)
            updateScreen();
            bg.drawLine(0,0,i,400);     // drawn in background color (XORed)
        }
       
        bg.dispose();                   // dispose graphics context
        bImage.flush();                 // flush (empty) image
    }
   
    private void updateScreen() {
        g2d.drawImage(bImage, 0, 0, this);  // load buffer to screen
    }
}

Author:  Homer_simpson [ Sun Feb 22, 2004 7:19 pm ]
Post subject: 
ummm... dude... how do i run a program that doesn't have a main method :S
Author:  rizzix [ Mon Feb 23, 2004 3:45 pm ]
Post subject: 
Java:
import javax.swing.*;
import java.awt.Dimension;

public class Test {
    public static void main(String[] args) {
        // initialised with the title for the title bar
        JFrame frame = new JFrame("Test Application");
        Dimension screenSize = frame.getToolkit().getScreenSize();
        frame.setBounds(screenSize.width/4, screenSize.height/4,
                        screenSize.width/2, screenSize.height/2);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
         
         int w = frame.getBounds().width;
         int h = frame.getBounds().height;

        frame.getContentPane().add(new DrawView(w, h));
        frame.show();
    }
}
Author:  Homer_simpson [ Tue Feb 24, 2004 6:01 pm ]
Post subject: 
makes me feel such a noobie at this... Embarassed
Author:  rizzix [ Tue Feb 24, 2004 11:25 pm ]
Post subject: 
yea, it might take awhile to get used to. u basically need to think Objects heh.

anyways..
the DrawView class i wrote above is basically this:
i create an image (its better if you use a BufferedImage.. but Image will do)
now i do all my drawing onto this image. when i need to update the screen, i just load the image on to the screen.

to make this process simpler i wrote this: http://www.compsci.ca/v2/viewtopic.php?t=3817

try it out.. i've wraped a turing like syntax over the java methods.. so it should be easier to concentrate on drawing than the actual process of buffering etc..

here's an example using that class:
Java:
import java.awt.*;
import javax.swing.JFrame;

class DrawView extends BufferedCanvas {
       
        DrawView(JFrame parent) {
            super(parent);
        }
       
        protected void offscreenPaint() {
            for (int i = 0; i < maxx(); i++)
            {
                drawline(0, 0 ,i, 400, Color.white);
                drawfilloval(0, 0, i, i, Color.red);
                update();
                drawline(0, 0, i, 400);
                drawfilloval(0, 0, i, i);
            }
        }
}


and here's the application class:
Java:
import javax.swing.*;
import java.awt.Dimension;
import java.awt.Color;

public final class Test {
    public static void main(String[] args) {
        JFrame frame = new JFrame("Test Application");
        Dimension screenSize = frame.getToolkit().getScreenSize();
        frame.setBounds(screenSize.width/4, screenSize.height/4,
                        screenSize.width/2, screenSize.height/2);
        frame.getContentPane().add(new DrawView(frame));
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.show();
    }
}

:


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