java - Rendering BufferedImage in JTable cell

Question

I need to display a BufferedImage in one JTable column. I overwrote JTable method

@Override
public Class<?> getColumnClass(int column) {
    if (column == 1){
        return BufferedImage.class;
    }
    return super.getColumnClass(column);
}

But I am still obtaining String representation of the object instead of image itself.Does anyone have idea what I am missing?

Answer 1

I'd populate the column that needs to show an image with ImageIcons and have the getColumnClass() method return Icon.class, and then render it with a JLabel that displays the Icon. In fact, I believe that the DefaultCellRenderer really is a JLabel, and so it should already know how to handle Icons.

Yep, all the model needs is to know that it holds Icons. For example, this code below works in the program below:

  DefaultTableModel model = new DefaultTableModel(COL_NAMES, 0) {
     @Override
     public Class<?> getColumnClass(int column) {
        if (getRowCount() > 0) {
           return getValueAt(0, column).getClass();
        }

        return super.getColumnClass(column);
     }
  };

For example:

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

import javax.imageio.ImageIO;
import javax.swing.*;
import javax.swing.table.DefaultTableModel;

public class ImageColumnTest2 {
   public static final String IMAGE_SHEET_PATH = "http://speckycdn.sdm.netdna-cdn.com/"
         + "wp-content/uploads/2010/08/flag_icons_04.jpg";
   public static final String[] COUNTRIES = {
      "Denmark", "China", "Chile", "Canada", "Belgium", "Austria",
      "Argentina", "France", "Malaysina", "Lebanon", "Korea", "Japan",
      "Italy", "Ireland", "India", "Hong Kong", "Greece", "Germany"
   };
   public static final int COLS = 6;
   public static final int ROWS = 3;
   private static final String[] COL_NAMES = {"Country", "Flag"};

   private JTable table = new JTable();
   private JScrollPane mainPane = new JScrollPane(table);

   public ImageColumnTest2() throws IOException {
      DefaultTableModel model = new DefaultTableModel(COL_NAMES, 0) {
         @Override
         public Class<?> getColumnClass(int column) {
            if (getRowCount() > 0) {
               return getValueAt(0, column).getClass();
            }

            return super.getColumnClass(column);
         }
      };
      URL url = new URL(IMAGE_SHEET_PATH);
      BufferedImage img = ImageIO.read(url);
      int x1 = 15;  // sorry about the magic numbers
      img = img.getSubimage(x1, 0, img.getWidth() - 2 * x1, img.getHeight());

      int y1 = 20 ;  // ditto!
      int w = img.getWidth() / COLS;
      int h = img.getHeight() / ROWS;
      for (int row = 0; row < ROWS; row++) {
         int y = (row * img.getHeight()) / ROWS;
         for (int col = 0; col < COLS; col++) {
            int x = (col * img.getWidth()) / COLS;
            BufferedImage subImg = img.getSubimage(x, y, w, h);

            subImg = subImg.getSubimage(x1, 0, subImg.getWidth() - 2 * x1, subImg.getHeight() - y1);

            ImageIcon icon = new ImageIcon(subImg);
            String country = COUNTRIES[col + row * COLS];
            Object[] rowData = {country, icon};
            model.addRow(rowData);
         }
      }


      table.setModel(model);
      table.setRowHeight(((ImageIcon)model.getValueAt(0, 1)).getIconHeight());
   }

   public JComponent getMainComponent() {
      return mainPane;
   }

   private static void createAndShowGui() {
      ImageColumnTest2 imgColumnTest = null;
      try {
         imgColumnTest = new ImageColumnTest2();
      } catch (MalformedURLException e) {
         e.printStackTrace();
         System.exit(-1);
      } catch (IOException e) {
         e.printStackTrace();
         System.exit(-1);
      }

      JFrame frame = new JFrame("ImageColumnTest");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.getContentPane().add(imgColumnTest.getMainComponent());
      frame.pack();
      frame.setLocationByPlatform(true);
      frame.setVisible(true);
   }

   public static void main(String[] args) {
      SwingUtilities.invokeLater(new Runnable() {
         public void run() {
            createAndShowGui();
         }
      });
   }
}