Question

I’m trying to create a custom cell renderer that will display an image in JTable’s header cell. I’ve gotten the source code to work with the Metal L&F but I am encountering problems with Nimbus. Under normal circumstances, Nimbus displays the image just fine. However, when a table is sorted, Nimbus will draw the sort icon instead of the icon I’ve specified. This is different than the Metal L&F, as that will always draw the icon I’ve provided.

Does anyone know of a way to have Nimbus draw the image even if a column is sorted?

I’m using Java 6.29 & Nimbus. I can’t change the Java release or the L&F.

Also, I’ve tried to do some other workarounds, like changing the label to use HTML and and img tag to display the image, but this produces a weird visual effect. EDIT The text and image aren’t aligned well (even with a HTML align tag on the img tag) Here is a picture, notice how the text in the Temp Hi column doesn’t align:

import java.awt.Component;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.table.DefaultTableCellRenderer;
import javax.swing.table.TableCellRenderer;


public class ImageChangeDemo extends JFrame {
    public static void main(String args[]) {
        //comment out the code below to try in Metal L&F
        try {
            for(javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.
                    getInstalledLookAndFeels()) {
                if("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        }
        catch(Exception ex) {
            ex.printStackTrace();
        }

        java.awt.EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                new ImageChangeDemo().setVisible(true);
            }
        });
    }

    public ImageChangeDemo(){
        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        JScrollPane pane = new javax.swing.JScrollPane();
        JTable table = new javax.swing.JTable();
        table.setAutoCreateRowSorter(true);
        table.setModel(new javax.swing.table.DefaultTableModel(
            new Object [][] {
                {"a", "q", "h", "v"},
                {"b", "m", "l", "h"},
                {"d", "c", "a", "d"},
                {"j", "o", "y", "e"}
            },
            new String [] {
                "Col 1", "Col 2", "Col 3", "Col 4"
            }
        ) {
            Class[] types = new Class [] {
                String.class, String.class, String.class, String.class
            };
            @Override
            public Class getColumnClass(int columnIndex) {
                return types [columnIndex];
            }
        });
        pane.setViewportView(table);
        this.add(pane);

        table.getTableHeader().setDefaultRenderer(new ImageRenderer(table));

        pack();
    }

    public class ImageRenderer extends DefaultTableCellRenderer{
        TableCellRenderer orig;
        ImageIcon icon;
        ImageRenderer(JTable table){
            orig = table.getTableHeader().getDefaultRenderer();
        }
        @Override
        public Component getTableCellRendererComponent(final JTable table, Object value, boolean isSelected, boolean hasFocus, int row, int column) {
            Component c = 
                    orig.getTableCellRendererComponent(
                        table, value, isSelected, hasFocus, row, column);
            if(c instanceof JLabel){
                if(true){
                    JLabel label = (JLabel)c;
                    label.setIcon(makeIcon());
                }
            }
            return c;
        }

        public ImageIcon makeIcon(){
            if(icon == null)
            icon = new ImageIcon(
                    ImageChangeDemo.class.getResource("/resources/green_triangle_down.png"));
            return icon;
        }
    }
}

EDIT: Here is an example scenario of what my real application should do: If the table column contains certain data (such as any strings beginning with a certain word) display a warning icon next to the column name in the table header. I’ve gotten this to work fine. Now, if the user sorts a column with the image, Nimbus is removing the image and replacing it with a sort icon – I still want the original warning icon to display.

Answer 1

So after much trial and error I was able to figure out a way to have my custom icon in the header row even if the column is sorted. Basically what I did was have the renderer return a custom panel containing 2 children, the image in a JLabel and the component that was originally produced by default renderer. (Note that this workaround is only necessary for Nimbus L&F, and the original example code works fine in the Metal L&F)

This code uses StackLayout created by Romain Guy as demonstrated in his book Filthy Rich Clients – see page p245. Here is the source for StackLayout

Here is the code I created for the renderer. Make sure to download StackLayout else this won’t compile.

import java.awt.Component;
import java.awt.Dimension;
import java.awt.FontMetrics;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.table.DefaultTableCellRenderer;
import javax.swing.table.TableCellRenderer;


public class ImageChangeDemo extends JFrame {
    public static void main(String args[]) {
        //comment out the code below to try in Metal L&F
        try {
            for(javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.
                    getInstalledLookAndFeels()) {
                if("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        }
        catch(Exception ex) {
            ex.printStackTrace();
        }

        java.awt.EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                new ImageChangeDemo().setVisible(true);
            }
        });
    }

    public ImageChangeDemo(){
        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        JScrollPane pane = new javax.swing.JScrollPane();
        JTable table = new javax.swing.JTable();
        table.setAutoCreateRowSorter(true);
        table.setModel(new javax.swing.table.DefaultTableModel(
            new Object [][] {
                {"a", "q", "h", "v"},
                {"b", "m", "l", "h"},
                {"d", "c", "a", "d"},
                {"j", "o", "y", "e"}
            },
            new String [] {
                "Col 1", "Col 2", "Col 3", "Col 4"
            }
        ) {
            Class[] types = new Class [] {
                String.class, String.class, String.class, String.class
            };
            @Override
            public Class getColumnClass(int columnIndex) {
                return types [columnIndex];
            }
        });
        pane.setViewportView(table);
        this.add(pane);


        pack();
        //set renderer after pack so header row has correct default height
        table.getTableHeader().setDefaultRenderer(new ImageRenderer(table));


    }

    public class ImageRenderer extends DefaultTableCellRenderer{
        TableCellRenderer orig;
        private final ImageIcon icon = new ImageIcon(
                    ImageChangeDemo.class.getResource("/resources/exclamation-icon.png"));;
        private JPanel jp = new JPanel(new StackLayout());
        private final JLabel pic = new JLabel(icon);
        { //extra initialization for PIC
            pic.setHorizontalAlignment(JLabel.LEADING); //so it isn't centered in stack layout
        }

        ImageRenderer(JTable table){
            orig = table.getTableHeader().getDefaultRenderer();
        }

        @Override
        public Component getTableCellRendererComponent(final JTable table, Object value, boolean isSelected, boolean hasFocus, int row, int column) {
            Component c = 
                    orig.getTableCellRendererComponent(
                        table, value, isSelected, hasFocus, row, column);
            if(true){
                int width  = table.getColumnModel().getColumn(column).getWidth();
                int height = table.getTableHeader().getSize().height;
                System.out.println("height"+height);

                jp.removeAll();                //clean the JPanel

                //move text in label to the left so it isn't covered by the icon
                if(c instanceof JLabel){
                    JLabel l = (JLabel) c;
                    l.setPreferredSize(new Dimension(width, height));

                    FontMetrics fontMetrics = l.getFontMetrics(l.getFont());
                    int sizeOfSpace = fontMetrics.charWidth(' ');
                    int numSpaces = (int)Math.round(icon.getIconWidth() / (double)sizeOfSpace);
                    StringBuilder sb = new StringBuilder();
                    for(int i = 0; i < numSpaces; i++)
                        sb.append(' ');

                    //account for HTML in header messages
                    if(l.getText().toLowerCase().startsWith("<html>")){
                        l.setText(  l.getText().substring(0, "<html>".length()) +
                                    sb.toString() +
                                    l.getText().substring("<html>".length()));
                    }
                    else
                        l.setText(sb.toString()+l.getText());
                }


                //Add components to the JPanel & return it.
                jp.add(c, StackLayout.BOTTOM);  //will contain modifications for spacing.
                jp.add(pic, StackLayout.TOP);
                return jp;

            }
            else
                return c;
        }
    }
}