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Pixel perfect graphics in Java swing/awt

Is there a way to achieve pixel perfect graphics in Swing/AWT components?
I am implementing a custom border for a button by extending AbstractBorder. For demonstration purpose thickness is always equal to 3 and each line is painted using different color.
import javax.swing.*;
import javax.swing.border.AbstractBorder;
import javax.swing.border.Border;
import javax.swing.plaf.basic.BasicLookAndFeel;
import java.awt.*;
public class ExampleFrame extends JFrame {
public ExampleFrame() {
init();
}
public static void main(String[] args) throws UnsupportedLookAndFeelException
{
UIManager.setLookAndFeel(new CustomLookAndFeel());
ExampleFrame frame = new ExampleFrame();
frame.setVisible(true);
}
private void init() {
setLayout(new BorderLayout());
JPanel panel = new JPanel();
panel.setLayout(new GridBagLayout());
getContentPane().add(panel, BorderLayout.NORTH);
GridBagConstraints constraints = new GridBagConstraints();
JButton button1 = new JButton("aaa");
button1.setVerticalTextPosition(JButton.BOTTOM);
button1.setHorizontalTextPosition(JButton.CENTER);
button1.setFocusable(false);
constraints.insets = new Insets(2, 2, 2, 2);
constraints.gridx = 0;
constraints.gridy = 0;
constraints.gridwidth = 1;
constraints.gridheight = 3;
constraints.fill = GridBagConstraints.BOTH;
constraints.anchor = GridBagConstraints.LINE_START;
panel.add(button1, constraints);
JButton button2 = new JButton("bbb");
button2.setHorizontalAlignment(JButton.CENTER);
button2.setFocusable(false);
constraints.gridx = 1;
constraints.gridy = 0;
constraints.gridwidth = 1;
constraints.gridheight = 1;
constraints.fill = GridBagConstraints.BOTH;
constraints.anchor = GridBagConstraints.LINE_START;
panel.add(button2, constraints);
JButton button3 = new JButton("eee");
button3.setHorizontalAlignment(JButton.CENTER);
button3.setFocusable(false);
constraints.gridx = 1;
constraints.gridy = 1;
constraints.gridwidth = 1;
constraints.gridheight = 1;
constraints.fill = GridBagConstraints.HORIZONTAL;
constraints.anchor = GridBagConstraints.LINE_START;
panel.add(button3, constraints);
JButton button4 = new JButton("ddd");
button4.setHorizontalAlignment(JButton.CENTER);
button4.setFocusable(false);
constraints.gridx = 1;
constraints.gridy = 2;
constraints.gridwidth = 1;
constraints.gridheight = 1;
constraints.fill = GridBagConstraints.HORIZONTAL;
constraints.anchor = GridBagConstraints.LINE_START;
panel.add(button4, constraints);
pack();
}
private static final class CustomBorder extends AbstractBorder {
private final int thickness;
public CustomBorder() {
this(1);
}
public CustomBorder(int thickness) {
this.thickness = thickness;
}
#Override
public void paintBorder(Component c, Graphics g, int x, int y, int width, int height) {
((Graphics2D) g).setRenderingHint(RenderingHints.KEY_STROKE_CONTROL, RenderingHints.VALUE_STROKE_PURE);
// ((Graphics2D) g).setRenderingHint(RenderingHints.KEY_STROKE_CONTROL, RenderingHints.VALUE_STROKE_NORMALIZE);
((Graphics2D) g).setStroke(new BasicStroke(1.0f));
for (int i = 0; i < thickness; i++) {
switch (i) {
case 0: {
g.setColor(Color.RED);
}
break;
case 1: {
g.setColor(Color.GREEN);
}
break;
case 2: {
g.setColor(Color.BLUE);
}
break;
}
// top-left -> top-right
g.drawLine(x, y + i, x + width, y + i);
// top-left > bottom-left
g.drawLine(x + i, y, x + i, y + height);
}
}
#Override
public Insets getBorderInsets(Component c, Insets insets) {
insets.top = thickness;
insets.bottom = thickness;
insets.left = thickness;
insets.right = thickness;
return insets;
}
}
private static final class CustomLookAndFeel extends BasicLookAndFeel {
#Override
protected void initComponentDefaults(UIDefaults table) {
super.initComponentDefaults(table);
// button
Border buttonBorder = new CustomBorder(3);
table.put("Button.border", buttonBorder);
table.put("Button.background", new Color(150, 150, 182));
table.put("Button.foreground", Color.BLACK);
}
#Override
public String getName() {
return "custom";
}
#Override
public String getID() {
return "custom";
}
#Override
public String getDescription() {
return "custom";
}
#Override
public boolean isNativeLookAndFeel() {
return false;
}
#Override
public boolean isSupportedLookAndFeel() {
return true;
}
}
}
Even though all 3 buttons have the same border parameters I get different border width and colors displayed.
VALUE_STROKE_PURE and VALUE_STROKE_NORMALIZE hints give different results, but none of them is pixel accurate.
Buttons "bbb", "eee" and "ddd" on the right side have the same width and height, but still the colors and total width of the border is different. Additionally, the default stroke that is being used has width of 1.0f.
I assume this happens, because Java 2D geometry operates on floating point numbers. Is there any way to overcome this limitation?
I tried different routines e.g. drawRect and different anti-aliasing hints, but no luck.

How to change color of paintComponent from another class

I have an oval component on a panel in OvalShape.java that I would like to change the color of
public class OvalShape extends JPanel {
private int diameter = 100;
private Color myColor = Color.RED;
//create the actual panel
public OvalShape() {
Dimension size = getPreferredSize();
size.width = 300;
size.height= 300;
setPreferredSize(size);
setBorder(BorderFactory.createLoweredSoftBevelBorder());
}
public void setMyColor(Color theColor) {
this.myColor = theColor;
}
//create the oval
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.fillOval(0, 0, diameter, diameter);
g.setColor(myColor);
}
//method for setting the diameter
public void setDiameter(int newDiameter) { //method to create diameter
//if diam invalid set to 10
diameter = (newDiameter >=0 ? newDiameter : 10);
repaint(); //repaint panel
}
}
from OvalPanel.java I want to be able to change the color. Here is what that class looks like
public class OvalPanel extends JPanel {
public int diameter = 100; //default diameter of the oval
public JSlider diamSlider;
public JLabel diamLabel;
public OvalShape ovalShape;
public OvalPanel() {
Dimension size = getPreferredSize();
size.width = 500;
setPreferredSize(size);
//create components
diamSlider = new JSlider(SwingConstants.HORIZONTAL, 0, 300, 100);
diamSlider.setSnapToTicks(true);
diamSlider.setMajorTickSpacing(100);
diamSlider.setMinorTickSpacing(25);
diamSlider.setPaintTicks(true);
diamSlider.setPaintLabels(true);
diamLabel = new JLabel("Diameter = " + diameter);
ovalShape = new OvalShape();
ovalShape.setDiameter(diamSlider.getValue());
ovalShape.setMyColor(Color.RED);
//set listeners
diamSlider.addChangeListener(new ChangeListener() {
#Override
public void stateChanged(ChangeEvent e) {
diamLabel.setText("Diameter = " + diamSlider.getValue());
ovalShape.setDiameter(diamSlider.getValue());
}
});
//set layout
setLayout(new GridBagLayout());
GridBagConstraints gbc = new GridBagConstraints();
////////first row////////
gbc.gridx = 0;
gbc.gridy = 0;
add(ovalShape, gbc);
////////second row////////
gbc.gridx = 0;
gbc.gridy = 1;
add(diamSlider, gbc);
////////third row////////
gbc.gridx = 0;
gbc.gridy = 2;
add(diamLabel, gbc);
}
but I don't really understand why this isn't working. The oval just comes out black. I have tried to apply the same theory that I did when creating the diameter slider as I am able to change the diameter of the oval using the slider in OvalPanel.java
Thanks for any help

g.fillOval(0, 0, diameter, diameter);
g.setColor(myColor);
You need to set the color BEFORE you paint the oval.

Java Swing JPanel paintComponents never called

I'm having an issue with a JPanel and I don't get what's going on. So I have a JFrame with a init function, that create a custom JPanel called GamePanel, and the strange thing is it never goes in the paintComponents function, even if I use repaint on the object.
Here is my code when I initialize the JPanel (in a JFrame):
this.gamePanel = new GamePanel(this.grid, this);
this.panel.add(this.gamePanel, constraints);
And the JPanel itself:
public class GamePanel extends JPanel {
private final int SQUARE_SIZE = 50;
private Grid grid;
private final GameView gameView;
public GamePanel(Grid grid, GameView gameView) {
this.gameView = gameView;
this.setPreferredSize(new Dimension(200, 200));
}
public void setGrid(Grid grid) {
this.grid = grid;
this.setPreferredSize(new Dimension(grid.getSizeX() * SQUARE_SIZE, grid.getSizeY() * SQUARE_SIZE));
}
#Override
public void paintComponents(Graphics g) {
System.out.println("test");
if (this.grid != null) {
Graphics2D g2 = (Graphics2D) g;
double thickness = 3;
g2.setStroke(new BasicStroke((float) thickness));
g2.setColor(Color.BLACK);
for (int i = 0; i < 3; i++) {
for (int j = 0; j < 3; j++) {
int x = SQUARE_SIZE * i;
int y = SQUARE_SIZE * j;
g2.drawRect(x, y, SQUARE_SIZE, SQUARE_SIZE);
if(this.grid.getSquareState(x, y) != 0) {
char[] tmp = ("" + this.grid.getSquareState(x, y)).toCharArray();
g2.drawChars(tmp, 0, 1, x, y);
}
}
}
}
}
}
EDIT: (the whole JFrame)
public class GameView extends JFrame {
private CustomSocket socket;
private JPanel panel;
private GamePanel gamePanel;
private JLabel listPlayers;
private JLabel playerPlaying;
private Grid grid;
public GameView(CustomSocket socket) {
this.socket = socket;
this.setTitle("TicTacToe - Client");
this.setSize(600, 480);
this.setLocationRelativeTo(null);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.init();
this.pack();
this.setVisible(true);
this.play();
}
private void init() {
this.panel = new JPanel();
this.panel.setLayout(new GridBagLayout());
GridBagConstraints constraints =new GridBagConstraints();
constraints.fill = GridBagConstraints.CENTER;
constraints.gridx = 0;
constraints.gridy = 0;
constraints.gridwidth = 1;
// Grid
this.gamePanel = new GamePanel(this.grid, this);
this.panel.add(this.gamePanel, constraints);
// Labels
constraints.gridy += 1;
this.listPlayers = new JLabel();
this.panel.add(this.listPlayers, constraints);
constraints.gridy += 1;
this.playerPlaying = new JLabel();
this.panel.add(this.playerPlaying, constraints);
this.setContentPane(this.panel);
}
private void play() {
String[] tmp = this.socket.getData().split(";");
this.grid = new Grid(Integer.parseInt(tmp[0]), Integer.parseInt(tmp[1]));
String players = "";
for(int i = 2; i < tmp.length; i++) {
players += tmp[i] + " ";
}
this.listPlayers.setText(players);
boolean notFinished = true;
while(notFinished) {
String[] gridData = this.socket.getData().split(";");
for(int i = 1; i < gridData.length; i++) {
String[] gridRow = gridData[i].replace("(", "").replace(")", "").split(",");
for(int j = 0; j < gridRow.length; j++) {
this.grid.setSquareState(i - 1, j, Integer.parseInt(gridRow[j]));
}
}
this.gamePanel.repaint();
String playerPlaying = this.socket.getData().split(";")[0];
if(playerPlaying != this.socket.getUsername()) {
}
notFinished = true;
}
}
}
Thank you in advance.

this.panel.add(this.gamePanel, constraints);
You add the component to a panel, but the panel doesn't have a preferred size. Since its size is (0, 0) there is nothing to paint so the method is never called.
All Swing components are responsible for determining their own preferred size. Override the getPreferredSize() method of your custom component. Then the layout manager can set the proper size/location of the component.
And paintComponent(...) is the proper method to override and don't forget the super.paintComponent(...) as the first statement to make sure the background gets cleared.

Prevent a component from being added to a jpanel if another component is already in place

So I am in the process of creating a game similar to Plants vs Zombies, however I've run into a slight problem: before I can apply the finishing touches such as levels, I need to prevent more than one JLabel being added to a JPanel. The placing of the JLabel works fine, though I think that I may have gone a roundabout route. The problem as stated above is that another JLabel can currently be added below a pre-existing JLabel. How do I set a JPanel to accept no more than the original component (the initial JLabel)? Any assistance would be greatly appreciated.
private final JFrame FRAME;
private final JPanel squares[][] = new JPanel[8][11];
private final Color DGY = Color.DARK_GRAY;
private final Color GRN = Color.GREEN;
private final Color BLK = Color.BLACK;
private final Color LGY = Color.LIGHT_GRAY;
private final Color GRY = Color.GRAY;
private final Color BLU = Color.BLUE;
private final Font F1 = new Font("Tahoma", 1, 36);
private String icon = "";
private int lvl = 10;
private void squareGen(int i, int j, Color col, boolean border)
{
squares[i][j].setBackground(col);
if (border)
{
squares[i][j].setBorder(BorderFactory.createLineBorder(BLK, 1));
}
FRAME.add(squares[i][j]);
}
public GameGUI()
{
FRAME = new JFrame("ESKOM VS SA");
FRAME.setSize(1600, 900);
FRAME.setLayout(new GridLayout(8, 11));
for (int x = 0; x < 8; x++)
{
if (x > 1 && x < 7)
{
squares[x][0] = new JPanel();
squareGen(x, 0, GRN, true);
} else if (x == 1 || x == 7)
{
squares[x][0] = new JPanel();
squareGen(x, 0, DGY, true);
} else
{
squares[x][0] = new JPanel();
squareGen(x, 0, BLU, false);
}
for (int y = 1; y < 11; y++)
{
squares[x][y] = new JPanel();
if (x == 0)
{
squareGen(x, y, BLU, false);
} else if (y == 10 || x == 1 || x == 7)
{
squareGen(x, y, DGY, true);
} else
{
squareGen(x, y, LGY, true);
addDToPanel(x, y);
}
}
}
JButton btnPause = new JButton();
btnPause.setText("||");
btnPause.setFont(F1);
btnPause.addActionListener(new java.awt.event.ActionListener()
{
#Override
public void actionPerformed(java.awt.event.ActionEvent evt)
{
btnPauseActionPerformed(evt);
}
});
squares[7][10].add(btnPause);
addButtons(8);
FRAME.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
FRAME.setLocationRelativeTo(null);
}
public void restart()
{
FRAME.dispose();
GameGUI ggui = new GameGUI();
ggui.setVisible(true);
}
public void mainMenu()
{
FRAME.dispose();
new StartUpUI().setVisible(true);
}
private void btnPauseActionPerformed(java.awt.event.ActionEvent evt)
{
new PauseGUI(this).setVisible(true);
}
private void btnAddDefenseActionPerformed(java.awt.event.ActionEvent evt)
{
JButton btn = (JButton) evt.getSource();
icon = btn.getActionCommand();
}
private void addButtons(int x)
{
JButton[] btn = new JButton[x];
for (int j = 1; j <= x; j++)
{
btn[j - 1] = new JButton();
ImageIcon ii = new ImageIcon(this.getClass().getResource("" + j + ".png"));
btn[j - 1].setIcon(ii);
btn[j - 1].setActionCommand("" + j);
btn[j - 1].setText("");
btn[j - 1].setForeground(btn[j - 1].getBackground());
squares[0][j].add(btn[j - 1]);
btn[j - 1].addActionListener(new java.awt.event.ActionListener()
{
#Override
public void actionPerformed(java.awt.event.ActionEvent evt)
{
btnAddDefenseActionPerformed(evt);
}
});
}
}
private void addDToPanel(int x, int y)
{
squares[x][y].addMouseListener(new MouseAdapter()
{
#Override
public void mousePressed(MouseEvent me)
{
JPanel panel = (JPanel) me.getSource();
int j = (int) (panel.getX() / 145.45454545) + 1;
int i = (int) (panel.getY() / 112.5) + 1;
addDefense(i, j, icon);
icon = "";
FRAME.revalidate();
FRAME.repaint();
}
});
}
private void addDefense(int i, int j, String imageName)
{
try
{
JLabel jlbl = new JLabel();
ImageIcon ii = new ImageIcon(this.getClass().getResource(imageName + ".png"));
jlbl.setIcon(ii);
squares[i][j].add(jlbl, java.awt.BorderLayout.CENTER);
} catch (Exception e)
{
}
}
public void setLvl(int lvl)
{
this.lvl = lvl;
}
public void setVisible(boolean b)
{
FRAME.setVisible(b);
}
This is not my main class, this class is instantiated in the main class and setVisible() = true;
Again thanks in advance!

How do I set a JPanel to accept no more than the original
You can use the Container.getComponentCount() method to check how many components have been added to the panel.
Only add your component when the count is 0.

SwingWorker process() updating gui Generics

Im trying to use SwingWorker to update my gui.
The part of my gui that I'm trying to update is a JPanel (gridPanel) with a GridLayout [50][50].
Each grid in the GridLayout has a custom GridGraphic JComponent.
In the doInBackground() of my SwingWorker, I update each GridGraphic which represents some color. Then, I publish it to a List that the process() uses to update the gui. Though, the gui isn't updating.
Is there a way to do this without calling repaint().
How do I fix my SwingWorker so the gui is responsive. What do I want to return in order for the gridPanel, which is a [50][50] GridLayout of GridGraphic components responsive to changes
The SwingWorker is executed in the stepButton.addActionListener(new ActionListener()...............in SlimeGui
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import javax.swing.event.*;
public class SlimeGui extends JFrame{
private JPanel buttonPanel, populationPanel, velocityPanel;
private JPanel gridPanel = new JPanel(new GridLayout(50, 50));
private JButton setupButton, stepButton, goButton;
private JLabel populationNameLabel, velocityNameLabel, populationSliderValueLabel, velocitySliderValueLabel;
private JSlider populationSlider, velocitySlider;
private GridGraphic [] [] gridGraphic;
private GridGraphic test;
private int agents = 125;
private int velocity = 500;
private boolean resetGrid;
public SlimeGui() {
setLayout(new GridBagLayout());
GridBagConstraints c = new GridBagConstraints();
//Set up JButtons
buttonPanel = new JPanel();
setupButton = new JButton("Setup");
stepButton = new JButton("Step");
goButton = new JButton("Go");
buttonPanel.add(setupButton);
buttonPanel.add(stepButton);
buttonPanel.add(goButton);
c.gridx = 0;
c.gridy = 1;
c.gridwidth = 3;
add(buttonPanel, c);
//Set up population JSlider
populationPanel = new JPanel();
populationNameLabel = new JLabel(" Population");
populationSliderValueLabel = new JLabel(Integer.toString(agents));
populationSlider = new JSlider(JSlider.HORIZONTAL,0, 1000, 125);
populationSlider.setMajorTickSpacing(125);
populationSlider.setPaintTicks(true);
populationSlider.addChangeListener(new PopulationSliderListener());
populationPanel.add(populationNameLabel);
populationPanel.add(populationSlider);
populationPanel.add(populationSliderValueLabel);
c.gridx = 0;
c.gridy = 2;
add(populationPanel, c);
//Set up veolicty JSlider
velocityPanel = new JPanel();
velocityNameLabel = new JLabel(" Velocity");
velocitySliderValueLabel = new JLabel(Integer.toString(velocity));
velocitySlider = new JSlider(JSlider.HORIZONTAL,0, 1000, 500);
velocitySlider.setMajorTickSpacing(125);
velocitySlider.setPaintTicks(true);
velocitySlider.addChangeListener(new VelocitySliderListener());
velocityPanel.add(velocityNameLabel);
velocityPanel.add(velocitySlider);
velocityPanel.add(velocitySliderValueLabel);
c.gridx = 0;
c.gridy = 3;
add(velocityPanel, c);
//Set up grid with GridGraphic objects
gridGraphic = new GridGraphic[50][50];
for(int i = 0; i < 50; i++){
for(int j = 0; j < 50; j++){
gridGraphic[i][j] = new GridGraphic();
gridPanel.add(gridGraphic[i][j]);
}
}
c.gridx = 0;
c.gridy = 0;
c.gridwidth = 3;
add(gridPanel, c);
//Set up ActionListener for the 'Setup' JButton
setupButton.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e) {
int n1=0;
int n2=0;
//resets the grid so there are no agents
if(resetGrid){
for(int i = 0; i < 50; i++){
for(int j = 0; j < 50; j++){
gridGraphic[i][j].setDefault();
}
}
}
//sets a random number of positions for GridGraphics
for (int numOfAgenets = 0; numOfAgenets < agents; numOfAgenets++){
int lowerB = 0;
int upperB = 50;
n1 = (lowerB + (int)(Math.random()*(upperB-lowerB))); //random number 1
n2 = (lowerB + (int)(Math.random()*(upperB-lowerB))); //random number 2
System.out.println("Choosing random agent "+(numOfAgenets+1)+": "+n1 +" "+n2);
//sets the GridGraphic to an agent if it's available
if (gridGraphic[n1][n2].getIntensity() == 0)
gridGraphic[n1][n2].setAgent();
//if the GridGraphic is already an agent, it continues to search
else if(gridGraphic[n1][n2].getIntensity() == 5){
while(gridGraphic[n1][n2].getIntensity() == 5){
n1 = (lowerB + (int)(Math.random()*(upperB-lowerB)));
n2 = (lowerB + (int)(Math.random()*(upperB-lowerB)));
}
gridGraphic[n1][n2].setAgent();
}
}
repaint();
resetGrid = true;
}
});
//Set up ActionListener for the 'Step' JButton
stepButton.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e) {
StepManager step = new StepManager(SlimeGui.this);
step.execute();
//repaint();
}
});
}
class PopulationSliderListener implements ChangeListener{
public void stateChanged(ChangeEvent e){
agents = ((JSlider)e.getSource()).getValue();
populationSliderValueLabel.setText(Integer.toString(agents));
System.out.println("Population of agents: " + agents);
}
}
class VelocitySliderListener implements ChangeListener{
public void stateChanged(ChangeEvent e){
velocity = ((JSlider)e.getSource()).getValue();
velocitySliderValueLabel.setText(Integer.toString(velocity));
System.out.println("Velocity(ms) of agents: " + velocity);
}
}
public Integer getVelocity(){
return velocity;
}
public GridGraphic getGridGraphic(int n1, int n2){
return gridGraphic[n1][n2];
}
public GridGraphic [][] getGridGraphic(){
return gridGraphic;
}
public void setGridGraphicArray(GridGraphic xxx, int n1, int n2 ){
gridGraphic[n1][n2] = xxx;
}
public void setGridPanel(GridGraphic[][] xxx){
for(int i = 0; i < 50; i++){
for(int j = 0; j < 50; j++){
gridPanel.add(xxx[i][j]);
}
}
}
/**
* Create the GUI and show it. For thread safety,
* this method should be invoked from the
* event-dispatching thread.
*/
private static void createAndShowGUI() {
//Create and set up the window.
SlimeGui slime = new SlimeGui();
slime.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//Display the window.
slime.pack();
slime.setVisible(true);
slime.setResizable(false);
}
public static void main(String[] args) {
//Schedule a job for the event-dispatching thread:
//creating and showing this application's GUI.
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}
});
}
}
My SwingWorker
import java.util.List;
import java.awt.*;
import javax.swing.*;
import java.util.concurrent.ExecutionException;
public class StepManager extends SwingWorker<Void, GridGraphic>{
private SlimeGui gui;
public StepManager(SlimeGui sg){
gui=sg;
}
#Override
protected Void doInBackground() throws Exception{
for(int i = 0; i < 50; i++){
for(int j = 0; j < 50; j++){
if(gui.getGridGraphic(i,j).getIntensity()==5){
if (i==0){
gui.getGridGraphic(i,j).setDefault();
gui.getGridGraphic(49,j).setAgent();
}
else{
gui.getGridGraphic(i,j).setDefault();
gui.getGridGraphic(i-1,j).setAgent();
}
}
publish(gui.getGridGraphic(i,j));
}
}
return null;
}
#Override
protected void process(List <GridGraphic> gg){
int k=0;
for ( int i = 0; i < 50; i++ ){
for(int j = 0; j < 50; j++){
gui.setGridGraphicArray(gg.get(k),i,j);
k++;
}
}
gui.setGridPanel(gui.getGridGraphicArray());
System.out.println("process has completed");
}
#Override
protected void done(){
System.out.println("doInBackground has completed");
}
}
My GridGraphic
import java.awt.*;
import javax.swing.*;
public class GridGraphic extends JComponent {
private int intensity = 0;
public GridGraphic() {
//setBorder(BorderFactory.createLineBorder(Color.BLUE));
}
public void paintComponent(Graphics g) {
//paints the GridGraphic black
if (intensity == 0){
super.paintComponent(g);
g.setColor(Color.BLACK);
g.fillRect(0, 0, getWidth(), getHeight());
}
//paints the GridGraphic black with a yellow dot
else if (intensity == 5){
super.paintComponent(g);
g.setColor(Color.BLACK);
g.fillRect(0, 0, getWidth(), getHeight());
g.setColor(Color.YELLOW);
g.fillOval(3, 3, getWidth()/2, getHeight()/2);
}
//paints the GridGraphic dark yellow (pheromone)
if (intensity == 2){
super.paintComponent(g);
g.setColor(Color.BLACK.brighter());
g.fillRect(0, 0, getWidth(), getHeight());
}
}
public Dimension getPreferredSize() {
return new Dimension(10, 10);
}
public void setAgent(){
intensity = 5;
}
public void setPheromone1(){
intensity = 2;
}
public void setDefault(){
intensity = 0;
}
public int getIntensity(){
return intensity;
}
}

The line number in the stack trace indicates where the exception occurs. Your gui attribute in StepManager is null. It's never initialized.