How to make my game scroll more smoothly ?

Question

Hello! I'm new at Java, however I have some programming experience.
I would like to make a tile engine. On the following link is an example of what I have so far:
[link-->|http://members.home.nl/bramdenhond/testjava/]
If you move your mouse over the area, the world scrolls.
However, I don't think it scrolls smoothly enough.
In the tutorial I was following, this technique was recommended for double-buffering:
        //** Update - Method, implements double buffering */
        public void update (Graphics g)
              // initialize buffer
              if (dbImage == null)
                    dbImage = createImage (this.getSize().width, this.getSize().height);
                    dbg = dbImage.getGraphics ();
              // clear screen in background
              dbg.setColor (getBackground ());
              dbg.clearRect(0, 0, this.getSize().width, this.getSize().height);
              //dbg.fillRect (0, 0, this.getSize().width, this.getSize().height);
              // draw elements in background
              dbg.setColor (getForeground());
              paint (dbg);
              // draw image on the screen
              g.drawImage (dbImage, 0, 0, this);
        }For the timing, I'm using a Thread, as recommended in the tutorial:
         public void start ()
              // define a new thread
              Thread th = new Thread (this);
              // start this thread
              th.start ();
          public void run ()
              // lower ThreadPriority
              Thread.currentThread().setPriority(Thread.MIN_PRIORITY);
              // run a long while (true) this means in our case "always"
              while (true)
                    // repaint the applet
                    repaint();
                    try
                          // Stop thread for 20 milliseconds
                          Thread.sleep (2);
                    catch (InterruptedException ex)
                          // do nothing
                    // set ThreadPriority to maximum value
                    Thread.currentThread().setPriority(Thread.MAX_PRIORITY);
           }I was wondering if someone if this is indeed the best approach, and if there are
any alternatives.
Thanks!

Answer 1

Hi all,
I've changed this source code so I can move the character from bottom to up but scrolling background is up to bottom. How I can change this class for scrolling background from up to down and not viceversa?
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.image.BufferedImage;
import java.awt.Image;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.MediaTracker;
import java.awt.Toolkit;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
public class JAniDemo {
  private BufferedImage biBackground = null;
  private Toolkit tk;
  private JFrame f;
  JAniDemo(){
    tk = Toolkit.getDefaultToolkit();
    f = new JFrame("AniDemo 1.0");
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    loadBackground("C:\\image.png");
    myPanel p = new myPanel(biBackground);
    f.add(p);
    f.pack();
    f.setVisible(true);
  private void loadBackground(String fn){
    Image im = tk.getImage(fn);
    MediaTracker mt = new MediaTracker(f);
    mt.addImage(im,0);
    try{
      mt.waitForID(0);
      biBackground = new BufferedImage(800, 641, BufferedImage.TYPE_INT_RGB);
      Graphics2D g2 = biBackground.createGraphics();
      g2.drawImage(im, 0, 0, null);
      g2.dispose();
    }catch(InterruptedException e){
      System.out.println(e.toString());
  public static void main(String[] args) {
    new JAniDemo();
  class myPanel extends JPanel implements ActionListener{
    private BufferedImage background;
    private BufferedImage bi = null;
    private int upperCorner = 0;
    int width;
    int height;
    myPanel(BufferedImage bg){
      super();
      background = bg;
      width = background.getWidth()/2;
      height = background.getHeight();
      bi = background.getSubimage(0,upperCorner,width,height);
      setPreferredSize(new Dimension(width, height));
      Timer t = new Timer(25, this);
      t.start();
    public void actionPerformed(ActionEvent e){ 
      upperCorner -= 1;
      if(UpperCorner >= height) UpperCorner = 38;  // adjust to make rollover seemless
      bi = background.getSubimage(0,UpperCorner,width,height);
      repaint();
    public void paintComponent(Graphics g){
      g.drawImage(bi, 0, 0, this);
}Please see this changes of original source code:
bi = background.getSubimage(0,upperCorner,width,height);
width = background.getWidth()/2;
if(UpperCorner >= height) // for vertical
upperCorner -= 1; // for up to down scrolling
Can you help me? Thanks.
Regards.
Edited by: Rapworld on Jun 9, 2010 11:19 AM