Background under column header

[viral]

I have small problem. I would like to change color under column header when I am draging column to change its order.

Try this simple code and drag columns. You will notice GRAY rectangle under header. How can I change it ?

import java.awt.Color;
import java.awt.EventQueue;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import javax.swing.table.JTableHeader;
import javax.swing.GroupLayout;
import javax.swing.GroupLayout.Alignment;
import javax.swing.JScrollPane;
import javax.swing.JTable;


public class MainWindow extends JFrame {

	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;
	private JPanel contentPane;
	private JTable table;

	/**
	 * Launch the application.
	 */
	public static void main(String[] args) {
		EventQueue.invokeLater(new Runnable() {
			public void run() {
				try {
					MainWindow frame = new MainWindow();
					frame.setVisible(true);
				} catch (Exception e) {
					e.printStackTrace();
				}
			}
		});
	}

	/**
	 * Create the frame.
	 */
	public MainWindow() {
		setBackground(Color.GREEN);
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		setBounds(100, 100, 450, 300);
		contentPane = new JPanel();
		contentPane.setBackground(Color.CYAN);
		contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
		setContentPane(contentPane);
		
		JScrollPane scrollPane = new JScrollPane();
		GroupLayout gl_contentPane = new GroupLayout(contentPane);
		gl_contentPane.setHorizontalGroup(
			gl_contentPane.createParallelGroup(Alignment.LEADING)
				.addGroup(gl_contentPane.createSequentialGroup()
					.addComponent(scrollPane, GroupLayout.DEFAULT_SIZE, 427, Short.MAX_VALUE)
					.addGap(5))
		);
		gl_contentPane.setVerticalGroup(
			gl_contentPane.createParallelGroup(Alignment.LEADING)
				.addGroup(gl_contentPane.createSequentialGroup()
					.addComponent(scrollPane, GroupLayout.DEFAULT_SIZE, 260, Short.MAX_VALUE)
					.addGap(3))
		);
		
		String[] columnNames = {"Column 1",
                "Column 2",
                "Column 3"};
		
		Object [] [] data = new Object [15][3];
		for (int i = 0; i < data.length; i++){
			data [i][0] = 322 + (i * 3) + (1213*i)/3;
			data [i][1] = "Some string";
			data [i][2] = "Another string in column";					
		}
		table = new JTable(data , columnNames);		
		table.setForeground(Color.YELLOW);
		table.setFillsViewportHeight(true);
		table.setBackground(Color.MAGENTA);
		scrollPane.setViewportView(table);
				
		scrollPane.getViewport().setBackground(Color.RED);
		
		contentPane.setLayout(gl_contentPane);
		JTableHeader anHeader = table.getTableHeader();
	    anHeader.setForeground(Color.WHITE);
	    anHeader.setBackground(Color.BLUE);
	    
	    // This gives nullpointer
	    //scrollPane.getColumnHeader().setBackground(Color.RED);
		
	    
	    
	}
}

Or check this screenshot :


Thanks in advance.

[DarrylBurke]

// This gives nullpointer
//scrollPane.getColumnHeader().setBackground(Color.RED);

Put that code after the JScrollPane has been realized by being added to a top level window that is subsequently pack()ed or setVisible(true)

....add(scrollPane);
:
:
frame.pack();
scrollPane.getColumnHeader().setBackground(Color.RED);

db

[DarrylBurke]

Alternatively, you can explicitly set the scroll pane's column header view.

JScrollPane scrollPane = new JScrollPane(table);
scrollPane.setColumnHeaderView(table.getTableHeader());
scrollPane.getColumnHeader().setBackground(Color.red);

db

[viral]

I do not understand first example - I am not experienced enough but second works.
Thanks DarrylBurke !

Problem solved.