how to add gradient background to JTable column header?

Question

Hi how to set gradient background to column header ? I have Jtable:

JTable table = new JTable(4, 5);

and try to setColor: table.getTableHeader().setBackground(Color.blue);

but with no succes color of column header is still same and these is just one color and I need gradient thx for help

Answer 1

Are you coding this with NetBean's code generation or are you coding your Swing by hand?

Have you tried creating a class that extends the JTableHeader and overrides its paintComponent method? Give it a try and in that method create a GradientPaint object or one of its variants use it to set the Graphics2D paint's property and then call fillRect using the current dimensions of the component to fill it with gradient color.

For example here are two ways to do this, one with a custom JTableHeader and one with a custom cell renderer that is used by the table header:

import java.awt.*;
import javax.swing.*;
import javax.swing.table.*;

public class GradientHeader {
   private static void createAndShowGui() {
      JTable table1 = new JTable();
      GradientTableHeader gradientTableHeader = new GradientTableHeader();
      gradientTableHeader.setColumnModel(table1.getColumnModel());
      table1.setTableHeader(gradientTableHeader);

      DefaultTableModel model = new DefaultTableModel(new Integer[][] {
            { 1, 2 }, { 3, 4 } }, new String[] { "A", "B" });

      table1.setModel(model);

      JTable table2 = new JTable(model);
      table2.getTableHeader().setDefaultRenderer(new MyCellRenderer());

      JPanel mainPanel = new JPanel(new GridLayout(1, 0));
      mainPanel.add(new JScrollPane(table1));
      mainPanel.add(new JScrollPane(table2));

      JFrame frame = new JFrame("GradientHeader");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.getContentPane().add(mainPanel);
      frame.pack();
      frame.setLocationRelativeTo(null);
      frame.setVisible(true);
   }

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

class GradientTableHeader extends JTableHeader {
   private static final Color COLOR_1 = new Color(255, 0, 0, 240);
   private static final Color COLOR_2 = new Color(0, 0, 255, 120);
   private static final float SIDE = 50;
   private GradientPaint gradientPaint = new GradientPaint(0, 0, COLOR_1, SIDE,
         SIDE, COLOR_2, true);

   @Override
   protected void paintComponent(Graphics g) {
      super.paintComponent(g);
      Graphics2D g2 = (Graphics2D) g;
      g2.setPaint(gradientPaint);
      g2.fillRect(0, 0, getWidth(), getHeight());
   }
}

class MyCellRenderer extends JPanel implements TableCellRenderer {
   private static final Color COLOR_1 = new Color(255, 0, 0, 200);
   private static final Color COLOR_2 = new Color(0, 0, 255, 200);
   private static final float SIDE = 50;
   private GradientPaint gradientPaint = new GradientPaint(0, 0, COLOR_1, SIDE,
         SIDE, COLOR_2, true);
   private JLabel label = new JLabel();

   public MyCellRenderer() {
      setOpaque(true);
      setLayout(new BorderLayout());
      add(label, BorderLayout.CENTER);
      label.setHorizontalAlignment(SwingConstants.CENTER);
   }

   @Override
   public Component getTableCellRendererComponent(JTable table, Object value,
         boolean isSelected, boolean hasFocused, int arg4, int arg5) {
      label.setText(value.toString());
      return this;
   }

   @Override
   protected void paintComponent(Graphics g) {
      super.paintComponent(g);
      Graphics2D g2 = (Graphics2D) g;
      g2.setPaint(gradientPaint);
      g2.fillRect(0, 0, getWidth(), getHeight());
   }
}