JButton will not change update image when using .setIcon(ICON);

Question

I already checked this duplicate question and other similar ones and it didn't help. I am trying to add an png to a button when it is clicked. The program is a variable sized tic-tac-toe game for school.

Right now I have:

private ImageIcon X_MARK = new ImageIcon("x.png");
private ImageIcon O_MARK = new ImageIcon("o.gif");
private JButton[][] cells;

...

    cells = new JButton[size][size];
    JPanel board = new JPanel(new GridLayout(size, size));
    board.setBorder(new LineBorder(Color.BLACK, 1));

    ButtonListener listener = new ButtonListener();

    for (int i = 0; i < size; i++)
        for (int j = 0; j < size; j++) {
            cells[i][j] = new JButton();
            cells[i][j].addActionListener(listener);
            board.add(cells[i][j]);
        }
    JFrame ttt = new JFrame();
    ttt.add(board);
    ttt.setTitle("Show GUI Components");
    ttt.setSize(60*size, 60*size);
    ttt.setLocation(0, 0);
    ttt.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    ttt.setVisible(true);

...

class ButtonListener implements ActionListener {
    @Override
    public void actionPerformed(ActionEvent e) {

        int i, j;

        for (i = 0; i < size; i++)
            for (j = 0; j < size; j++)
                if (e.getSource() == cells[i][j]) {
                    if ((i + j) % 2 == 0) {
                        cells[i][j].setBackground(Color.GREEN);
                        cells[i][j].setIcon(X_MARK);
                    } else {
                        cells[i][j].setBackground(Color.CYAN);
                        cells[i][j].setIcon(O_MARK);
                    }
                }

    }
}

That is all the relevant code I think. I am using Eclipse and I have x.png and o.png in the src folder and the bin folder of the the project. I have also tried a couple of variants I have seen on SO and google searches like, new ImageIcon("C:/Users/BigBoy/workspace_1/EventDriven/src/x.png");, new ImageIcon("src/x.png");, and some other ones involving getClass().getResource among other things. I don't know what else to try. I know I've done this in the past and didn't have this much trouble.

I added .setBackground(Color.GREEN); just to make sure my clicks were registering properly and they are, the problem to me seems to be with the declaring/initializing of the ImageIcon.

NOTE: Right now my button listener just makes the checker board pattern, I will get to actually putting each player's mark after I figure out this icon problem.

Answer 1

You need to understand resources which is what you will want to use. They are located relative to the class files. If the images are with the class files, then

• get your image as a resource
• Create an ImageIcon from the Image.

i.e., something like:

package whateverpackeyouareusing;

import java.awt.image.BufferedImage;
import java.io.IOException;
import java.net.URL;

import javax.imageio.ImageIO;
import javax.swing.Icon;
import javax.swing.ImageIcon;
import javax.swing.JOptionPane;


public class DefaultFoo {
   public static void main(String[] args) throws IOException {
      String resource = "x.png";
      URL url = Class.class.getResource(resource);
      BufferedImage img = ImageIO.read(url);
      Icon icon = new ImageIcon(img);
      JOptionPane.showMessageDialog(null, icon);
   }
}

---

Edit: A better example per Andrew Thompson:

package some.package;

import java.awt.Image;
import java.io.IOException;
import java.net.URL;

import javax.imageio.ImageIO;
import javax.swing.Icon;
import javax.swing.ImageIcon;
import javax.swing.JOptionPane;


public class PlayWithImages {
   public static final String X_RESOURCE = "x.png";
   private Icon xIcon;

   public PlayWithImages() throws IOException {
      URL xImgUrl = getClass().getResource(X_RESOURCE);
      Image xImg = ImageIO.read(xImgUrl);
      xIcon = new ImageIcon(xImg);
   }

   public Icon getXIcon() {
      return xIcon;
   }

   public static void main(String[] args) {
      try {
         PlayWithImages playWithImages = new PlayWithImages();
         Icon xIcon = playWithImages.getXIcon();
         JOptionPane.showMessageDialog(null, xIcon);
      } catch (IOException e) {
         e.printStackTrace();
      }

   }
}