Code for Double Buffering

Hi.
I did go through the JAVA tutorial here, but I still am not very clear about how to do double buffering. Can someone just give me a sample code? It would make my understanding clearer.
Also, for making games like mario or contra, should I use .gif images or .jpg?
Thanking You all

private Image offScreenImage;
private Graphics offScreen;
public void update(Graphics g){
offScreenImage=createImage(this.getSize().width, this.getSize().height);
offScreen=offScreenImage.getGraphics();
paint(offScreen);
g.drawImage(offScreenImage,0,0,this);
there you go... enjoy =)
Michael

Similar Messages

BDC Ok-Code for Double Click

Hi ,
Could anyone let me know the BDC OK Code for Double click.
I need to select a row by double clicking it in my recording but not able to capture the code for it.
Please do the needful.
Thanks in Advance,
Sowmmya B

Hi sowmmya,
1. If the row you are talking about is
   ALV Grid OO concepts,
   then i think there is a problem.
   It won't work with BDC as u are trying.
2. Well, for getting the code,
   before double clicking go in debug mode /H
   and then double click.
3. Now in deubbing mode,
see the value of sy-ucomm.
regards,
amit m.

Code for double clicking rows in alvgrido/p and moving it to internal tabl

hi,
code for double clicking rows in alvgrido/p and moving it to internal table

hi,
      see the following code which uses layout , double_click event in ALVGRID.
TABLES: mara,marc.
DATA:obj_custom TYPE REF TO cl_gui_custom_container,
     obj_alv TYPE REF TO cl_gui_alv_grid.
DATA: it_mara TYPE TABLE OF mara,
      wa_mara TYPE mara,
      wa_layout TYPE lvc_s_layo,
       wa_variant TYPE disvariant,
        x_save.
DATA:it_marc TYPE TABLE OF marc,
      wa_marc TYPE marc.
SELECT-OPTIONS: s_matnr FOR mara-matnr DEFAULT 1 TO 500.
START-OF-SELECTION.
SELECT * FROM mara INTO TABLE it_mara
    WHERE matnr IN s_matnr.
CALL SCREEN '100'.
      CLASS cl_dbclick DEFINITION
CLASS cl_dbclick DEFINITION.
PUBLIC SECTION.
    METHODS dbl FOR EVENT double_click OF cl_gui_alv_grid
      IMPORTING e_row e_column.
ENDCLASS.
DATA: obj1 TYPE REF TO cl_dbclick.
      CLASS cl_dbclick IMPLEMENTATION
CLASS cl_dbclick IMPLEMENTATION.
METHOD dbl.
    IF e_row-rowtype = space AND NOT e_row-index IS INITIAL.
      READ TABLE it_mara INDEX e_row-index INTO wa_mara.
    SELECT * FROM marc INTO TABLE it_marc
    WHERE matnr = wa_mara-matnr.
        CALL METHOD obj_custom->free
        EXCEPTIONS
          cntl_error        = 1
          cntl_system_error = 2
          OTHERS            = 3.
      IF sy-subrc <> 0.
   MESSAGE ID SY-MSGID TYPE SY-MSGTY NUMBER SY-MSGNO
              WITH SY-MSGV1 SY-MSGV2 SY-MSGV3 SY-MSGV4.
      ENDIF.
      CALL SCREEN '200'.
    ENDIF.
ENDMETHOD.                    "dbl
ENDCLASS.                    "cl_dbclick IMPLEMENTATION
*&      Module USER_COMMAND_0100 INPUT
      text
MODULE user_command_0100 INPUT.
CALL METHOD obj_custom->free
    EXCEPTIONS
      cntl_error        = 1
      cntl_system_error = 2
      OTHERS            = 3.
IF sy-subrc <> 0.
MESSAGE ID SY-MSGID TYPE SY-MSGTY NUMBER SY-MSGNO
             WITH SY-MSGV1 SY-MSGV2 SY-MSGV3 SY-MSGV4.
ENDIF.
CASE sy-ucomm.
    WHEN 'BACK'.
      LEAVE PROGRAM.
ENDCASE.
ENDMODULE.                 " USER_COMMAND_0100 INPUT
*&      Module filldata OUTPUT
      text
MODULE filldata OUTPUT.
CREATE OBJECT obj_custom
    EXPORTING
      container_name = 'CONTROL'.
CREATE OBJECT obj_alv
    EXPORTING
      i_parent = obj_custom.
CREATE OBJECT obj1.
SET HANDLER obj1->dbl FOR obj_alv.
CALL METHOD obj_alv->set_table_for_first_display
    EXPORTING
   i_buffer_active               =
   i_bypassing_buffer            =
   i_consistency_check           =
      i_structure_name              = 'MARA'
      is_variant                    = wa_variant
      i_save                        = x_save
   i_default                     = 'X'
      is_layout                     = wa_layout
   is_print                      =
   it_special_groups             =
   it_toolbar_excluding          =
   it_hyperlink                  =
   it_alv_graphics               =
   it_except_qinfo               =
   ir_salv_adapter               =
    CHANGING
      it_outtab                     = it_mara
   it_fieldcatalog               =
   it_sort                       =
   it_filter                     =
EXCEPTIONS
   invalid_parameter_combination = 1
   program_error                 = 2
   too_many_lines                = 3
   others                        = 4
IF sy-subrc <> 0.
MESSAGE ID SY-MSGID TYPE SY-MSGTY NUMBER SY-MSGNO
           WITH SY-MSGV1 SY-MSGV2 SY-MSGV3 SY-MSGV4.
ENDIF.
ENDMODULE.                 " filldata OUTPUT
*&      Module STATUS_0100 OUTPUT
      text
MODULE status_0100 OUTPUT.
SET PF-STATUS 'STATUS'.
SET TITLEBAR 'xxx'.
ENDMODULE.                 " STATUS_0100 OUTPUT
*&      Module STATUS_0200 OUTPUT
      text
MODULE status_0200 OUTPUT.
SET PF-STATUS 'STATUS'.
* SET TITLEBAR 'xxx'.
SUPPRESS DIALOG.
     SET PARAMETER ID 'MAT' FIELD wa_mara-matnr.
LEAVE TO LIST-PROCESSING AND RETURN TO SCREEN 0.
*WRITE:/ wa_mara-matnr,
       wa_mara-mbrsh,
       wa_mara-meins.
CREATE OBJECT obj_custom
    EXPORTING
      container_name = 'CONTROL'.
CREATE OBJECT obj_alv
    EXPORTING
      i_parent = obj_custom.
CALL METHOD obj_alv->set_table_for_first_display
    EXPORTING
   i_buffer_active               =
   i_bypassing_buffer            =
   i_consistency_check           =
      i_structure_name              = 'MARC'
   is_variant                    = wa_variant
   i_save                        = x_save
   i_default                     = 'X'
   is_layout                     = wa_layout
   is_print                      =
   it_special_groups             =
   it_toolbar_excluding          =
   it_hyperlink                  =
   it_alv_graphics               =
   it_except_qinfo               =
   ir_salv_adapter               =
    CHANGING
      it_outtab                     = it_marc
   it_fieldcatalog               =
   it_sort                       =
   it_filter                     =
EXCEPTIONS
   invalid_parameter_combination = 1
   program_error                 = 2
   too_many_lines                = 3
   others                        = 4
IF sy-subrc <> 0.
MESSAGE ID SY-MSGID TYPE SY-MSGTY NUMBER SY-MSGNO
           WITH SY-MSGV1 SY-MSGV2 SY-MSGV3 SY-MSGV4.
ENDIF.
ENDMODULE.                 " STATUS_0200 OUTPUT
*&      Module layout OUTPUT
      text
MODULE layout OUTPUT.
wa_layout-grid_title = 'MATERIAL DATA'.
wa_layout-zebra = 'X'.
wa_layout-edit = 'X'.
ENDMODULE.                 " layout OUTPUT
*&      Module variant OUTPUT
      text
MODULE variant OUTPUT.
wa_variant-report = 'ZALV_GRID1'.
x_save = 'A'.
ENDMODULE.                 " variant OUTPUT
*&      Module USER_COMMAND_0200 INPUT
      text
MODULE user_command_0200 INPUT.
CASE sy-ucomm.
    WHEN 'BACK'.
      CALL METHOD obj_custom->free
        EXCEPTIONS
          cntl_error        = 1
          cntl_system_error = 2
          OTHERS            = 3.
      IF sy-subrc <> 0.
MESSAGE ID SY-MSGID TYPE SY-MSGTY NUMBER SY-MSGNO
             WITH SY-MSGV1 SY-MSGV2 SY-MSGV3 SY-MSGV4.
      ENDIF.
      LEAVE TO SCREEN '100'.
ENDCASE.
ENDMODULE.                 " USER_COMMAND_0200 INPUT
thanks,
raji
reward if helpful

Double buffering still gives flickering graphics.

I copied code from a tutorail which is supposed to illustrate double buffering.
After I run it, it still flickers though.
I use applet viewer, which is part of netbeans to run my applet.
Link to tutorial: http://www.javacooperation.gmxhome.de/TutorialStartEng.html
My questions are:
Is the strategy used for double buffering correct?
Why does it flicker?
Why does the program change the priority a couple of times?
Can you make fast games in JApplets or is there a better way to make games? (I think C++ is too hard)
Here is the code:
package ballspel;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Image;
import javax.swing.JApplet;
//import java.applet.*;
* @author Somelauw
public class BallApplet extends /*Applet*/ JApplet implements Runnable {
private Image dbImage;
private Graphics dbg;
private int radius = 20;
private int xPos = 10;
private int yPos = 100;
* Initialization method that will be called after the applet is loaded
* into the browser.
@Override
public void init() {
//System.out.println(this.isDoubleBuffered()); //returns false
// Isn't there a builtin way to force double buffering?
// TODO start asynchronous download of heavy resources
@Override
public void start() {
Thread th = new Thread(this);
th.start();
public void run() {
Thread.currentThread().setPriority(Thread.MIN_PRIORITY);
while (true) {
xPos++;
repaint();
try {
Thread.sleep(20);
} catch (InterruptedException ex) {
ex.printStackTrace();
Thread.currentThread().setPriority(Thread.MAX_PRIORITY);
@Override
public void paint(Graphics g) {
super.paint(g);
//g.clear();//, yPos, WIDTH, WIDTH)
g.setColor(Color.red);
g.fillOval(xPos - radius, yPos - radius, 2 * radius, 2 * radius);
@Override
public void update(Graphics g) {
super.update(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.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);
// TODO overwrite start(), stop() and destroy() methods
}

Somelauw wrote:
I copied code from a tutorail which is supposed to illustrate double buffering.
After I run it, it still flickers though.
I use applet viewer, which is part of netbeans.. AppletViewer is part of the JDK, not NetBeans.
..to run my applet.
Link to tutorial: http://www.javacooperation.gmxhome.de/TutorialStartEng.html
Did you specifically mean the code mentioned on this page?
[http://www.javacooperation.gmxhome.de/BildschirmflackernEng.html]
Don't expect people to go hunting around the site, looking for the code you happen to be referring to.
As an aside, please use the code tags when posting code, code snippets, XML/HTML or input/output. The code tags help retain the formatting and indentation of the sample. To use the code tags, select the sample and click the CODE button.
Here is the code you posted, as it appears in code tags.
package ballspel;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Image;
import javax.swing.JApplet;
//import java.applet.*;
* @author Somelauw
public class BallApplet extends /*Applet*/ JApplet implements Runnable {
    private Image dbImage;
    private Graphics dbg;
    private int radius = 20;
    private int xPos = 10;
    private int yPos = 100;
     * Initialization method that will be called after the applet is loaded
     * into the browser.
    @Override
    public void init() {
        //System.out.println(this.isDoubleBuffered()); //returns false
        // Isn't there a builtin way to force double buffering?
        // TODO start asynchronous download of heavy resources
    @Override
    public void start() {
        Thread th = new Thread(this);
        th.start();
    public void run() {
        Thread.currentThread().setPriority(Thread.MIN_PRIORITY);
        while (true) {
            xPos++;
            repaint();
            try {
                Thread.sleep(20);
            } catch (InterruptedException ex) {
                ex.printStackTrace();
            Thread.currentThread().setPriority(Thread.MAX_PRIORITY);
    @Override
    public void paint(Graphics g) {
        super.paint(g);
        //g.clear();//, yPos, WIDTH, WIDTH)
        g.setColor(Color.red);
        g.fillOval(xPos - radius, yPos - radius, 2 * radius, 2 * radius);
    @Override
    public void update(Graphics g) {
        super.update(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.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);
    // TODO overwrite start(), stop() and destroy() methods
}Edit 1:
- For animation code, it would be typical to use a javax.swing.Timer for triggering updates, rather than implementing Runnable (etc.)
- Attempting to set the thread priority will throw a SecurityException, though oddly it occurs when attempting to set the Thread priority to maximum, whereas the earlier call to set the Thread priority to minimum passed without comment (exception).
- The paint() method of that applet is not double buffered.
- It is generally advisable to override paintComponent(Graphics) in a JPanel that is added to the top-level applet (or JFrame, or JWindow, or JDialog..) rather than the paint(Graphics) method of the top-level container itself.
Edited by: AndrewThompson64 on Jan 22, 2010 12:47 PM

Need help with double buffering

Hi!
I'm trying to write an animated applet the shows the Java Duke waving.
No problem getting it to work, but the applet is flickering and I sence the need for double buffering.
I've tried to use "traditional" double buffering techniques without success. Something like this:
currentDuke = bufferGraphics.getGraphics();
public void update(Graphics g) {
    bufferGraphics.clearRect(0, 0, this.getWidth(), this.getHeight());
    paint(g);
public void paint(Graphics g) {
    bufferGraphics.drawImage(nextDuke, 0, 0, this);
    g.drawImage(currentDuke, 0, 0, this);
}Didn't help...
Here's my current code:
import javax.swing.*;
import java.awt.*;
* This is a simple animation applet showing Duke waving.
* @author Andrew
* @version 1.0 2002-07-04
public class WavingDuke extends JApplet implements Runnable {
    private Image[] duke;
    private Image currentDuke;
    private Thread wave;
     * Called by the browser or applet viewer to inform this applet that it has
     * been loaded into the system.
    public void init() {
        loadDuke();
        currentDuke = this.createImage(this.getWidth(), this.getHeight());
     * Called by the browser or applet viewer to inform this applet that it
     * should start its execution.
    public void start() {
        if (wave == null) {
            wave = new Thread(this);
            wave.start();
     * Loads all the duke images into a <code>Image</code> array.
    private void loadDuke() {
        duke = new Image[10];
        for (int i = 0; i < 10; i++) {
            duke[i] = this.getImage(this.getCodeBase(), "images/duke"+i+".gif");
     * Method cycles through different images and calls <code>repaint</code>
     * to make an animation. After each call to <code>repaint</code> the thread
     * sleeps for predefined amount of time.
    public void run() {
        while (true) {
            for (int i = 0; i < 10; i++) {
                currentDuke = duke;
repaint();
paus(150);
* Method makes the current thread to sleep for tha amount of time
* specified in parameter <code>ms</code>.
* @param ms The time to wait specified in milliseconds.
private void paus(int ms) {
try {
Thread.sleep(ms);
} catch (InterruptedException ie) {
System.err.println(ie.getMessage());
* Updates this component.
* @param g The specified context to use for updating.
public void update(Graphics g) {
paint(g);
* Paints this component.
* @param g The graphics context to use for painting.
public void paint(Graphics g) {
g.clearRect(0, 0, this.getWidth(), this.getHeight());
g.drawImage(currentDuke, 0, 0, this);
Thanks in advance!
/Andrew

I've solved it!
/Andrew

How does buffer size affect double buffered waveform generation?

I had originally posted the following question:
"Why does the double buffered waveform generation pause after the first buffer before continuing?"
"I am using an AT-AO-10 board to generate a multiple channel waveform in double buffered mode. The board's DAC's are updated by an external clock signal. While the waveform generation performs well, I notice that after the first buffer has been generated there is a time delay before the next buffer is output. However the second buffer and thereafter perform well without any time delays. If anyone can provide me an explanation on why this happens I would appreciate it. I am using NI-DAQ API functions to generate the waveforms and my settings for the WFM_DB_Config function are 1 for oldDataStop to disallow regeneration of data and 0 for partialTransferStop to not stop when a half buffer is partially transferred."
-posted by Vadi on 6/7/2001
I received a response from Geneva as follows:
Geneva L. on 6/11/2001 says:
"Vadi,
The first thing is to make sure that you have the latest version of NI-DAQ installed, NI-DAQ 6.9.1. If you need to install it, make sure you completely uninstall any prior versions. Then, you will have examples installed in either the NI-DAQ or the CVI directory. In the AO directory, you should find the WFMdoubleBuf example.
Start with that to make sure the output appears as you expect. Then, you can modify it to apply your external update clock, following the idea presented in the WFMsingleBufExtUpdate example. You might even want to double-check that your external clock acts as you expect using an oscilloscope.
Finally, modify the example such that you can update on multiple channels, remembering that you interleave each channels buffer into one buffer for WFM_DB_Transfer. Whatever data is in the buffer will be updated on the output channels.
Regards,
Geneva L.
Applications Engineer
National Instruments"
I have checked my version of NI-DAQ and it is 6.9.1. I am generating the double buffered waveform according to the format shown in WFMdoubleBuf and with some modifications from WFMsingleBufExtUpdate to allow me to use my external update clock. However I continue to notice the same phenomena again and again. For a buffer size of 7500 or 10000 points there is a time lag meaning after the first buffer has been output there is a noticeable time delay before the second buffer and buffers there after is output. This time lag doesn't exist for the buffers that are output after the first buffer but it does exist for the first buffer. When I decrease the buffer size down to 5000 points the time lag disappears (Note: this phenomena also occurs when I use an internal time base as opposed to my external clock). Is there a reason for this? I am using a AT-AO-10 board and I know the on board FIFO is 1024 points deep. However from the documentation provided it doesn't indicate that double buffered mode uses the on board FIFO at all. In fact, the functions require that the FIFO mode be turned off (in WFM_Load) for double buffered waveform generation. Is there a reason why when the buffer size is increased that there is a time lag after the first buffer? Is this because of the functions themselves or is this because of the AT-AO-10 board?

Vadi,
Make sure that your buffer size is set to the same number of points that you're actually writing to the buffer initially. For instance, if you run the example as-is, the NIDAQMakeBuffer puts exactly the ulCount amount of data into the buffer. Then, it continuously writes out half buffers. Thus, if you are not writing enough data to fill up the buffer the first time, there will be that lag until the section where half buffers are output.
Regards,
Geneva L.
Applications Engineer
National Instruments
http://www.ni.com/ask

Which is better, Double Buffering 1, or Double Buffering 2??

Hi,
I came across a book that uses a completely different approach to double buffering. I use this method:
private Graphics dbg;
private Image dbImage;
public void update() {
if (dbImage == null) {
    dbImage = createImage(this.getSize().width, this.getSize().height);
    dbg = dbImage.getGraphics();
dbg.setColor(this.getBackground());
dbg.fillRect(0, 0, this.getSize().width, this.getSize().height);
dbg.setColor(this.getForeground());
paint(dbg);
g.drawImage(dbImage, 0, 0, this);
}that was my method for double buffering, and this is the books method:
import java.awt.*;
public class DB extends Canvas {
     private Image[] backing = new Image[2];
     private int imageToDraw = 0;
     private int imageNotDraw = 1;
     public void update(Graphics g) {
          paint(g);
     public synchronized void paint(Graphics g) {
          g.drawImage(backing[imageToDraw], 0, 0, this);
     public void addNotify() {
          super.addNotify();
          backing[0] = createImage(400, 400);
          backing[1] = createImage(400, 400);
          setSize(400, 400);
          new Thread(
               new Runnable() {
                    private int direction = 1;
                    private int position = 0;
                    public void run() {
                         while (true) {
                              try {
                                   Thread.sleep(10);
                              }catch (InterruptedException ex) {
                              Graphics g = backing[imageNotDraw].getGraphics();
                              g.clearRect(0, 0, 400, 400);
                                                g.setColor(Color.black);
                              g.drawOval(position, 200 - position, 400 - (2 * position), 72 * position);
                              synchronized (DB.this) {
                                   int temp = imageNotDraw;
                                   imageNotDraw = imageToDraw;
                                   imageToDraw = temp;
                              position += direction;
                              if (position > 199) {
                                   direction = -1;
                              }else if (position < 1) {
                                   direction = 1;
                              repaint();
          ).start();
     public static void main(String args[]) {
          Frame f = new Frame("Double Buffering");
          f.add(new DB(), BorderLayout.CENTER);
          f.pack();
          f.show();
}which is better? I noticed smoother animation with the later method.
Is there no difference? Or is it just a figment of my imagination??

To be fair if you download an applet all the class files are stored in your .jpi_cache, and depending on how that game requests its graphics sometimes they are stored there to, so really if you have to download an applet game twice, blame the programmer (I've probably got that dead wrong :B ).
But, what's wrong with Jars. They offer so much more.
No offence meant by this Malohkan but if you can't organize your downloaded files the internet must really be a landmine for you :)
Personally I'd be happy if I never seen another applet again, it seems java is tied to this legacy, and to the average computer user it seems that is all java is capable of.
Admitidly there are some very funky applets out here using lots of way over my head funky pixel tricks, but they would look so much better running full screen and offline.

Properly (?) Double Buffered Applet is really Choppy

Hi all. I looked around here for the proper way to double buffer an applet, and I think I've got it, but it's realllly choppy when it runs. (It's a little 2d jump 'n run game with not much in it yet). If you have any idea why, please tell =) Thanks!
public class Game extends JApplet implements KeyListener, Runnable
     //doublebuffer stuff
     Graphics bufferGraphics;
     Image offscreenImage;
     Dimension dim;
     //constants
     int SCREEN_WIDTH = 800;
     int SCREEN_HEIGHT = 600;
     int SPRITE_SIZE = 64;
     Color BGColor = Color.white;
     int PLAYER_SPEED_X = 10;
     int PLAYER_JUMP_SPEED = 20;
     int GRAVITY_ACCEL = 1;
     //directional constants
     int LEFT = -1;
     int RIGHT = 1;
     int STOPPED = 0;
     int UP = -1;
     int DOWN = 1;
     //images
     Image playerImage;
     //movement
     boolean freeFall = true;
     int playerDirX = STOPPED;
     int playerVelY = 0;
     int playerPosX = 0;
     int playerPosY = 0;
     //game control variables
     boolean gameIsRunning = false;
     Thread t;
     int i = 0;
     public void init()
          addKeyListener(this);
          gameIsRunning = true;
          //prepare offscreen image for double buffering
          setSize(800,600);
          dim = getSize();
          offscreenImage = createImage(dim.width,dim.height);
          bufferGraphics = offscreenImage.getGraphics();
          playerImage = getImage(getDocumentBase(),"images/playerRight.gif");
          t = new Thread(this);
          t.start();
     public void run()
          while(gameIsRunning)
               try
                    t.sleep(33);
               catch (InterruptedException e) {}
               playerPosX += playerDirX*PLAYER_SPEED_X;
               playerPosY -= playerVelY;
               if(freeFall)
                    playerVelY -= GRAVITY_ACCEL;
               //wraparound
               if(playerPosX < 0)
                    playerPosX = 0;
               if(playerPosX > SCREEN_WIDTH - SPRITE_SIZE)
                    playerPosX = SCREEN_WIDTH - SPRITE_SIZE;
               //stop at the floor
               if(playerPosY > SCREEN_HEIGHT - SPRITE_SIZE)
                    freeFall = false;
                    playerVelY = 0;
                    playerPosY = SCREEN_HEIGHT - SPRITE_SIZE;
               repaint();
     public void keyPressed(KeyEvent e)
          //move right
          if(e.getKeyCode() == KeyEvent.VK_RIGHT ||
                    e.getKeyCode() == KeyEvent.VK_D)
               playerImage = getImage(getDocumentBase(),"images/playerRight.gif");
               playerDirX = RIGHT;
          //move left
          if(e.getKeyCode() == KeyEvent.VK_LEFT ||
                    e.getKeyCode() == KeyEvent.VK_A)
               playerImage = getImage(getDocumentBase(),"images/playerLeft.gif");
               playerDirX = LEFT;
          //jump
          if(e.getKeyCode() == KeyEvent.VK_SPACE ||
                    e.getKeyCode() == KeyEvent.VK_W ||
                    e.getKeyCode() == KeyEvent.VK_UP)
               //allow jumping if we're standing on a surface
               if(playerPosY == SCREEN_HEIGHT - SPRITE_SIZE ||
                         playerPosX == 0 ||
                         playerPosX == SCREEN_WIDTH - SPRITE_SIZE)
                    if(playerPosX == 0)
                         playerDirX = RIGHT;
                         playerImage =
                              getImage(getDocumentBase(),"images/playerRight.gif");
                    if(playerPosX == SCREEN_WIDTH - SPRITE_SIZE)
                         playerDirX = LEFT;
                         playerImage =
                              getImage(getDocumentBase(),"images/playerLeft.gif");
                    freeFall = true;
                    playerVelY = PLAYER_JUMP_SPEED;
     public void keyReleased(KeyEvent e)
          //stop moving right
          if(e.getKeyCode() == KeyEvent.VK_RIGHT ||
                    e.getKeyCode() == KeyEvent.VK_D)
               if(playerDirX == RIGHT)
                    playerDirX = STOPPED;
          //stop moving left
          if(e.getKeyCode() == KeyEvent.VK_LEFT ||
                    e.getKeyCode() == KeyEvent.VK_A)
               if(playerDirX == LEFT)
                    playerDirX = STOPPED;
     public void keyTyped(KeyEvent e)
     public void paint(Graphics g)
          //clear screen
          bufferGraphics.setColor(Color.white);
          bufferGraphics.fillRect(0,0,SCREEN_WIDTH,SCREEN_HEIGHT);
          //draw the player
          bufferGraphics.drawImage(playerImage,playerPosX,playerPosY,this);
          g.drawImage(offscreenImage,0,0,this);
     public void stop()
          t.stop();
    public void update(Graphics g)
         paint(g);
}

It looks fine to me, but don't reload the player images every time. If you need a different image you should read up on AffineTransform and do some rotations etc, or at least have the 4 images in an array or something.
P.S. stop is deprecated for threads. If you are done with the thread null it. That being said, if you are making this as an applet, make sure you can restart or reload it properly by testing it with the appletvier.
Good luck in your work.

Double Buffering Slow..is it in the code? or..

Hi all..
i make small application which use double buffering..
here's the code:
public void update(Graphics g){
        tys_a=System.currentTimeMillis();
        Dimension d = getSize();
        if (offscreenImage == null || offscreenImage.getWidth(null) < d.width || offscreenImage.getHeight(null) < d.height){
            if (offscreenImage != null) offscreenImage.flush();
            offscreenImage = createImage(d.width, d.height);
            offscreenSize = d;
            offscreenGraphics = offscreenImage.getGraphics();
        offscreenGraphics.clearRect(0, 0, d.width, d.height);
        paint(offscreenGraphics);
        g.drawImage(offscreenImage, 0, 0, null);
        g.dispose();
        tys_b=System.currentTimeMillis();
        tys_c=tys_b-tys_a;
        System.out.println("DRAW OFFSCREEN GRAPH " + tys_c + " --- " + tys_a + " ---- " + tys_b);
    }then i run it on my desktop PC, which specs are
Core 2 duo E4500 - 2.20Ghz, 2 Gb RAM , Vista Home Premium
its works fine..took 10 ms
but when i try on Sony vaio laptop, which specs are:
core 2 duo T8100 - 2.1Gghz, 2Gb RAM, Vista home premium
its so slow..took average about 800-900ms (80-90 times slower)
did i do something wrong with my code...i've been searching all day...but seems no answer
but all i can think..is not about the code..because it works fine in my desktop...
but i dunno what cause this problem?
any body can help?or ever have this kind of problem willing to share?
Thx,

AndrewThompson64 wrote:
>
Hi,
dunnoIs this a English word???>Is this an English word? No it is not, it is strine* for "I do not know". I understand the Americans also know of this strine abbreviation, but I cannot understand how, since their comprehension of strine is quite low.
* local pronunciation of 'Australian'.
But to the OP. It is a far better idea to phrase your replies in standard English, since many people who understand English do not understand (or will not tolerate) local abbreviations and slang.In the South West of England It can be translated as "I don't know and I don't care" often accompanied by a shrug of the shoulders.

Double buffering for shape animation

Hello people,
I'm building an applet which animates some text (a shape with various setting for stroke, fill, etc.) and translating it from x1 to x2 using AffineTransform. How can I clear the screen to create an animation effect and double buffering to avoid flickering? Double buffering can be used with ImageS, but what about ShapeS?
Many thanks

Double buffering is a general concept that applies to all
graphic objects.

Problem with Double Buffering and Swing

Hi
I made a game and basically it works pretty well, my only problem is it flickers really badly right now. I read up on a whole lot of forums about double buffering and none of those methods seemed to work. Then I noticed that Swing has double buffering built in so I tried that but then I get compilation errors and I'm really not sure why. My original code was a console application and worked perfectly, then I ported it into a JApplet and it still works but it flickers and thats what I'm tryign to fix now.
The code below is in my main class under the constructor.
Heres the double buffering code I'm trying to use, I'm sure you all seen it before lol
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.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);
     }My paint is right under neath and heres how it looks
This snipet of code works but when I change the method to
public paintComponent(Graphics g){
super.paintComponent(g)...
everythign stops working and get a compilation error and says that it can't find paintComponent in javax.swing.JFrame.
public void paint(Graphics g)
          super.paint(g);
          //if game starting display menue
          if (show_menue)
               //to restart lives if player dies
               lives = 3;
               menue.draw_menue(g);
               menue_ufo1.draw_shape(g);
               menue_ufo2.shape_color = Color.DARK_GRAY;
               menue_ufo2.draw_shape(g);
               menue_ufo3.shape_color = Color.BLUE;
               menue_ufo3.draw_shape(g);
               menue_ufo4.shape_color = new Color(82, 157, 22);
               menue_ufo4.draw_shape(g);
               menue_ufo5.draw_shape(g);
               menue_ufo6.shape_color = new Color(130, 3, 3); ;
               menue_ufo6.draw_shape(g);
               menue_turret.draw_ship(g);
               menue_ammo.draw_ammo(g);
          else
               //otherwise redraw game objects
               gunner.draw_ship(g);
               y_ammo.draw_ammo(g);
               grass.draw_bar(g);
               o_ufo.draw_shape(g);
               b_ufo.draw_shape(g);
               m_ufo.draw_shape(g);
               s_ufo.draw_shape(g);
               z_ufo.draw_shape(g);
               xx_ufo.draw_shape(g);
               info.draw_bar(g);
               live_painter.draw_lives(g, lives);
               score_painter.draw_score(g, score);
               level_display.draw_level(g, level);
               explosion.draw_boom(g);
     }I just want to get rid of the flickering for now so any help will be greatly appreciated. Depending which will be simpler I can either try to double buffer this program or port it all to swing but I'm not sure which elements are effected by AWT and which by Swing. Also I read some of the Java documentation but couldn't really understand how to implement it to fix my program.
Thanks in advance
Sebastian

This is a simple animation example quickly thrown together. I have two classes, an animation panel which is a JPanel subclass that overrides paintComponent and draws the animation, and a JApplet subclass that simply holds the animation panel in the applet's contentpane:
SimpleAnimationPanel.java
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Point;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import javax.imageio.ImageIO;
import javax.swing.JPanel;
import javax.swing.Timer;
class SimpleAnimationPanel extends JPanel
    private static final int DELAY = 20;
    public static final int X_TRANSLATION = 2;
    public static final int Y_TRANSLATION = 2;
    private Point point = new Point(5, 32);
    private BufferedImage duke = null;
    private Timer timer = new Timer(DELAY, new TimerAction());
    public SimpleAnimationPanel()
        try
            // borrow an image from sun.com
            duke = ImageIO.read(new URL(
                    "http://java.sun.com/products/plugin/images/duke.wave.med.gif"));
        catch (MalformedURLException e)
            e.printStackTrace();
        catch (IOException e)
            e.printStackTrace();
        setPreferredSize(new Dimension(600, 400));
        timer.start();
    // do our drawing here in the paintComponent override
    @Override
    protected void paintComponent(Graphics g)
        super.paintComponent(g);
        if (duke != null)
            g.drawImage(duke, point.x, point.y, this);
    private class TimerAction implements ActionListener
        @Override
        public void actionPerformed(ActionEvent e)
            int x = point.x;
            int y = point.y;
            Dimension size = SimpleAnimationPanel.this.getSize();
            if (x > size.width)
                x = 0;
            else
                x += X_TRANSLATION;
            if (y > size.height)
                y = 0;
            else
                y += Y_TRANSLATION;
            point.setLocation(new Point(x, y)); // update the point
            SimpleAnimationPanel.this.repaint();
}AnimationApplet.java
import java.lang.reflect.InvocationTargetException;
import javax.swing.JApplet;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class AnimationApplet extends JApplet
    public void init()
        try
            SwingUtilities.invokeAndWait(new Runnable()
                public void run()
                    // construct the panel
                    JPanel simpleAnimation = new SimpleAnimationPanel();
                    // put it in the contentPane of the JApplet
                    getContentPane().add(simpleAnimation);
                    setSize(simpleAnimation.getPreferredSize());
        catch (InterruptedException e)
            e.printStackTrace();
        catch (InvocationTargetException e)
            e.printStackTrace();
}Here's a 3rd bonus class that shows how to put the JPanel into a stand-alone program, a JFrame. It's very similar to doing it in the JApplet:
AnimationFrame.java
import javax.swing.JFrame;
public class AnimationFrame
    private static void createAndShowUI()
        JFrame frame = new JFrame("SimpleAnimationPanel");
        frame.getContentPane().add(new SimpleAnimationPanel());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    public static void main(String[] args)
        java.awt.EventQueue.invokeLater(new Runnable()
            public void run()
                createAndShowUI();
}Edited by: Encephalopathic on Mar 15, 2008 11:01 PM

Alternative to Double-Buffered Canvas

I am working on a program in which I use a double-buffered Canvas inside a JScrollPane. The problem is that the Canvas draws over the scrollbars. I have tried extending JComponent, JPanel, JApplet, and Component instead of Canvas, and none of them are double buffered. Here is the code I used to debug this problem:
import java.awt.*;
import java.awt.geom.*;
import java.awt.image.*;
import javax.swing.*;
public class Test implements Runnable
     JFrame f;
     JScrollPane scroller;
     JPanel panel;
     TestCanvas canvas;
     Thread runner;
     BufferStrategy strategy;
     public static void main (String[] args) {
          Test app = new Test();
          app.init();
     public void init() {
          f = new JFrame();
          f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          panel = new JPanel();
          canvas = new TestCanvas();
          panel.add(canvas);
          scroller = new JScrollPane(panel);
          scroller.setWheelScrollingEnabled(true);
          f.getContentPane().add(scroller);
          f.pack();
          f.setSize(300,300);
          f.setVisible(true);
          canvas.createBufferStrategy(2);
          strategy = canvas.getBufferStrategy();
          runner = new Thread(this);
          runner.run();
     public void run() {
          int x = 0;
          while(x != 65536) {
               Graphics2D g = (Graphics2D)strategy.getDrawGraphics().create();
               g.setColor(new Color(x%256,0,0));
               g.fill(new Ellipse2D.Double(0,0,600,600));
               strategy.show();
               x++;
}Any suggestions?

The main culprit is that you are mixing AWT components with Swing ones.
In addition, your are doing so many of useless things and wrong things in your code.
Swing components are defaulted for using double-buffering.
See: http://java.sun.com/products/jfc/tsc/articles/painting/index.html
Try and study this code.
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.awt.image.*;
import javax.swing.*;
public class Fox1229{
JFrame f;
JScrollPane scroller;
TestCanvas canvas;
int x;
Timer t;
public static void main (String[] args) {
    Fox1229 app = new Fox1229();
    app.init();
public void init() {
    x = 0;
    f = new JFrame();
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    canvas = new TestCanvas();
    scroller = new JScrollPane(canvas);
    scroller.setWheelScrollingEnabled(true);
    f.getContentPane().add(scroller, BorderLayout.CENTER);
    f.setSize(300, 300);
    f.setVisible(true);
    t = new Timer(50, new ActionListener(){
      public void actionPerformed(ActionEvent e){
        canvas.setOc(new Color(x % 256, 0, 0));
        canvas.repaint();
        if (++x == 1024){
          t.stop();
    t.start();
class TestCanvas extends JPanel{
Color oc;
public TestCanvas (){
    oc = new Color(0, 0, 0);
public void setOc(Color c){
    oc = c;
public Dimension getPreferredSize(){
    return new Dimension(600, 600);
public void paintComponent(Graphics g){
    super.paintComponent(g);
    Graphics2D g2d = (Graphics2D)g;
    g2d.setColor(Color.blue);
    g2d.fill(new Rectangle(0, 0, 600, 600));
    g2d.setColor(oc);
    g2d.fill(new Ellipse2D.Double(0, 0, 600, 600));
}

Double buffering

I was searching through posts to find an answer to my problem of getting double buffering working without flickering when I came across this response:
Upgrade your SDK, early 1.4 implementations had this problem on Windows2k (It's a bug). Pretty much the second buffer will point to an empty portion of video memory always, the solution to this without updating is to fill the entire backbuffer completely, flip it, fill it again, and then flip it again. You should then be able to use it normaly.
-Jason Thomas.
Since I am on dialup I can't really download the SDK, so could someone give me some code to do what Jason has suggested?
Jonathan O'Brien

No I am not recreating the bufferstrategy every frame. Overriding update didn't work either. Here is my code for main:
          GraphicsEnvironment env = GraphicsEnvironment.getLocalGraphicsEnvironment();
          GraphicsDevice device = env.getDefaultScreenDevice();
          GraphicsConfiguration gc = device.getDefaultConfiguration();
          Frame myFrame = new Frame(gc);
BufferCapabilities bufferCaps = gc.getBufferCapabilities();
          boolean multiBuffer = bufferCaps.isMultiBufferAvailable();
          boolean fullScreen = device.isFullScreenSupported();
          System.out.println("Full screen supported = " + fullScreen);
          System.out.println("Multi buffer available = " + multiBuffer);
          System.out.println("Page flipping = " + bufferCaps.isPageFlipping());
          myFrame.setUndecorated(true);
          myFrame.setIgnoreRepaint(true);
          if ((fullScreen) && (multiBuffer))
               device.setFullScreenWindow(myFrame);
               device.setDisplayMode(new DisplayMode(800, 600, 16, 0));
               rectBounds = myFrame.getBounds();
               myFrame.createBufferStrategy(2);
               bufferStrategy = myFrame.getBufferStrategy();
               bufferReady = true;
          Game thisGame = new Game(args[0]);
          myFrame.add(thisGame);
//          myFrame.getContentPane().add(thisGame);
          myFrame.show();
And here is the relevant code for my run method:
          if (bufferReady)
               Graphics g = bufferStrategy.getDrawGraphics();
               if (!bufferStrategy.contentsLost()) {
                    g.fillRect(0,0,getWidth(),getHeight());
                    g.dispose();
                    bufferStrategy.show();

Double buffering images

HELP!!! lol i'm trying to figure out how to get the whole double buffering thing to work with a picture like a gif image i drew in paint. i can't quite understand anything aobut how to do it. lol i've read some things and looked at some code samples but they all do it with a polygon. i just can't seem to get it right. i learn best from code snipets if that helps. don't give me a whole program i just want some lines that will help me learn it like what i have to import. and other things. i know a little about using images but not a whole lot. if anyone can help it will be appreciated.
andy

Psst... Tell you teacher that one can read an image with ImageIO, often in one line:
BufferedImage image = ImageIO.read(file_or_url_or_inputstream);(No need for a MediaTracker!) And the resulting BufferedImage (a subclass of Image)
is easier to work with than Image and has more useful features.
Welcome to Java 2D.

Double buffering circle not round anymore

I am making an applet where some circles are painted to the screen. When not using the double buffering scenario, the shapes appear correctly.
The problem is when i use the double-buffering technique, the circles are still there, but they look like very ugly. I would call that some "squarcles".
What is the bug here and how to get some decent double buffering with thoses circles?

Ok, i had some problem with the running thread when closing the applet viewer, but now this situation is corrected by setting the animation thread to null before calling stop().
Maybe explanation of the problem is not clear, so i made two versions of the same applet with only 2 lines of code different so that there is one applet that is not double buffered.
You can check these by yourself at this place:
Double buffered circles: http://www.geocities.com/xeneve/cooltrail/ demo_cooltrail.htm
No double buffer:
http://www.geocities.com/xeneve/cooltrail/demo_cooltrail_ndb.htm
This is just annoying to get this result. I realise that maybe not many peoples are coding applets so i guess there is few people that may have a workaround for this.

Code for Double Buffering

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