Java graphics app prob regarding painting........ app does NOT use applets

Question

Hi ,
I basically want to write a java graphics game application ......At this point in time all I want to do is add a green rectangle to the content pane.......I can do this but I want to stick with OO concepts so I have various classes......the thing is ....when a user resizes the window the graphic I have painted dissapeared
I will show the classes I have used and the code below......I want to do the program conforming to the way I was tought java which is to have a main controlling class that orchestrates communication between unrelated classes and their methods. In addition to my question if anyone sees stuff fundementally wrong with my code and has a better solution please feel free to enlighten me :-)
main controlling class:
import java.awt.Graphics;
* <p>Title: </p>
* <p>Description: </p>
* <p>Copyright: Copyright (c) 2005</p>
* <p>Company: </p>
* @author not attributable
* @version 1.0
public class PoolApp {
public PoolApp() {
//creates new gamescreen object
GameScreen aScreen = new GameScreen(this);
public static void main(String[] args) {
PoolApp poolApp1 = new PoolApp();
public Graphics getPaintedTable(GameScreen aGameScreen) {
Paint aPaint = new Paint(this);
Graphics tblObj = aPaint.getTbleGraphic(aGameScreen);
return tblObj;
------end main controlling class
------TLayer Class start
import javax.swing.*;
/* The purpose of this class was to create a generic frame that would
be inherited from all screen classes ...I initially had this creating a black background that would be inherited from child classes but that created
more problems when the screen was resized by one of the child classes*/
public class TLayer extends JFrame {
public TLayer() {
-----TLayer Class end
-----GameScreen class start--------
public class GameScreen extends TLayer{
private PoolApp thePoolApp;
public GameScreen(PoolApp aPoolApp) {
thePoolApp = aPoolApp; //set a reference from here to the controlling PoolApp initGameScreen(); //initialise and show GameScreen .....screen
public void initGameScreen() {
this.setSize(800,600);
this.show();
//now make a request to the poolapp controlling class to ask for a painted green table and get the paint class to paint it to screen
thePoolApp.getPaintedTable(this);
----GameScreen class end------------
----PaintScreen class start-------------
PoolApp thePoolApp;
public Paint() {
public Paint(PoolApp apoolApp) {
thePoolApp = apoolApp;
public Graphics getTbleGraphic(GameScreen aGameScreen) {
Container theCont = aGameScreen.getContentPane(); //assign the gamescreen content pane to a container
theCont.setSize(200,200); //set a viewable size to the container
Graphics thetbl = theCont.getGraphics(); //get container graphics context and assign it to a graphics object
thetbl.setColor(Color.green); //color the object
thetbl.fillRect(30,30,20,60); //fill the rectangle
return thetbl; //return the object
---PaintScreen class end---------------
This code actually draws the green rectangle to the gamescreen from the paint class .......so it works to a degree! ......whenever I resize the window the painted image dissapears, could anyone suggest a way around this also ...am I going about this the correct way? Im open to making mass changes to better the program ......the only thing I do not want is to use applets! .....as I want to learn the fundementals of custom painting my stuff
Any help is much needed and appreciated
David

Answer 1

Hi .....I managed to fix my problem .....but I have really had to get my head around method overiding! ......Your advice is taken onboard ...also Im going to try and find a straight forward diagram of the java graphics heirrachy ......well the parts that are reasnable to what Im doing ......Also from what I know and what you have said yes threads would definately be the way to go as far as animation and paintings concerned...I plan to do some serious research on that as I progress.
I am going to post my basic working program ........I was wandering if you think this is an effiecent way I have done this? or if you could make any recommendations? its just I dont want to adopt this approach and find its no good when I get further into the programs development :-)) anyway heres the code :
------Class PoolApp start--------------
public class PoolApp {
  public PoolApp() {
    GameScreen aGScreen = new GameScreen(this);
  public static void main(String[] args) {
    PoolApp poolApp1 = new PoolApp();
}------Class PoolApp end--------------
------Class TLayer start--------------
import javax.swing.*;
import java.awt.Graphics;
public class TLayer extends JFrame {
  public TLayer() {
     System.out.println("In TLayer default constructor");
     this.setSize(800,600);
}------Class TLayer end--------------
------Class GameScreen start--------------
import java.awt.Graphics;
public class GameScreen extends TLayer {
  PoolApp thepoolApp;
  Table theTable;
  Graphics g;
  public GameScreen() {
   System.out.println("In gamescreen default constructor table");
  public GameScreen(PoolApp apoolApp) {
  thepoolApp = apoolApp;
  System.out.println("In gamescreen  constructor 2");
  addTable();
public void addTable() {
System.out.println("in addTable");
this.show();
//theTable = new Draw(this);
//theTable.setTable();
//theTable.paint(g);
public void paint(Graphics g) {
     System.out.println("In Gamescreen paint ");
     theTable = new Table(this);
     theTable.paint(g);
public void update(Graphics g) {
    System.out.println("In Gamescreen update ");
    theTable = new Table(this);
    theTable.paint(g);
}------Class GameScreen end--------------
------Class Table start--------------
import java.awt.Graphics;
import java.awt.Container;
import java.awt.Color;
public class Table extends TLayer{
  GameScreen thegameScreen;
  public Table() {
      System.out.println("In Table default constructor");
  public Table(GameScreen agameScreen) {
    thegameScreen = agameScreen;
    System.out.println("In Table 2nd constructor");
  public void paint(Graphics theGraphic) {
    System.out.println("In Table paint ");
    Container tablecont = thegameScreen.getContentPane();
    theGraphic = tablecont.getGraphics();
    theGraphic.setColor(Color.green);
    theGraphic.fillRect(310,220,180,80);
  public void update(Graphics theGraphic) {
       System.out.println("In Table update");
   paint(theGraphic);
}------Class Table end--------------
To be honest I would rather have created a table object then added it to the content pane ....but when i did it that way ......and I resized the screen the green table graphic dissapeared .....I would also have prefered all painting of the table to be done in the table class but I had the same problem of the graphic dissapearing when the window was resized and this is the best solution I have come up with as yet ....:-) .....any recommendations are greatly appreciated
Thanks
David