How to resize JScrollPane rowHeader

Question

The code bellow will generate this table:

As the image indicates, in this table you can resize the column A, B, ... But you cannot resize the column with the lowercase letters a,b,c,e... i.e., the rowHeader of the JScrollPane.

Any Ideas how can I do that?

package main;
// Example from http://www.crionics.com/products/opensource/faq/swing_ex/SwingExamples.html
/* (swing1.1beta3) */
import java.awt.BorderLayout;
import java.awt.Component;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

import javax.swing.AbstractListModel;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.ListCellRenderer;
import javax.swing.ListModel;
import javax.swing.UIManager;
import javax.swing.table.DefaultTableModel;
import javax.swing.table.JTableHeader;

/**
 * @version 1.0 11/09/98
 */

class RowHeaderRenderer extends JLabel implements ListCellRenderer {

  RowHeaderRenderer(JTable table) {
    JTableHeader header = table.getTableHeader();
    setOpaque(true);
    setBorder(UIManager.getBorder("TableHeader.cellBorder"));
    setHorizontalAlignment(CENTER);
    setForeground(header.getForeground());
    setBackground(header.getBackground());
    setFont(header.getFont());
  }

  public Component getListCellRendererComponent(JList list, Object value,
      int index, boolean isSelected, boolean cellHasFocus) {
    setText((value == null) ? "" : value.toString());
    return this;
  }
}

public class RowHeaderTable extends JFrame {

  public RowHeaderTable() {
    super("Row Header Example");
    setSize(300, 150);

    ListModel lm = new AbstractListModel() {
      String headers[] = { "a", "b", "c", "d", "e", "f", "g", "h", "i" };

      public int getSize() {
        return headers.length;
      }

      public Object getElementAt(int index) {
        return headers[index];
      }
    };

    DefaultTableModel dm = new DefaultTableModel(lm.getSize(), 10);
    JTable table = new JTable(dm);
    table.setAutoResizeMode(JTable.AUTO_RESIZE_OFF);

    JList rowHeader = new JList(lm);
    rowHeader.setFixedCellWidth(50);

    rowHeader.setFixedCellHeight(table.getRowHeight()
        + table.getRowMargin());
    //                           + table.getIntercellSpacing().height);
    rowHeader.setCellRenderer(new RowHeaderRenderer(table));

    JScrollPane scroll = new JScrollPane(table);
    scroll.setRowHeaderView(rowHeader);
    getContentPane().add(scroll, BorderLayout.CENTER);
  }

  public static void main(String[] args) {
      RowHeaderTable frame = new RowHeaderTable();
    frame.addWindowListener(new WindowAdapter() {
      public void windowClosing(WindowEvent e) {
        System.exit(0);
      }
    });
    frame.setVisible(true);
  }
}

The row headers are controlled differently from the `JTable`, you'll need to us, at the very least, a `MouseMoitionListener` and possible change the preferred size of the component/header — MadProgrammer, Dec 11 '15 at 01:20
Yeah, I thought that could be the case. I know little about implementing listeners though. Reference in that direction is already welcome. — pedroabreu, Dec 11 '15 at 03:54

score 2 · Accepted Answer · answered Dec 11 '15 at 04:22

As @MadProgrammer has already suggested, a MouseMotionListener is probably the only way to go here if not the easiest way. Here is your code modified:

package main;

import java.awt.BorderLayout;
import java.awt.Component;
import java.awt.Cursor;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import javax.swing.AbstractListModel;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.ListCellRenderer;
import javax.swing.ListModel;
import javax.swing.UIManager;
import javax.swing.table.DefaultTableModel;
import javax.swing.table.JTableHeader;

class RowHeaderRenderer extends JLabel implements ListCellRenderer {

  RowHeaderRenderer(JTable table) {
    JTableHeader header = table.getTableHeader();
    setOpaque(true);
    setBorder(UIManager.getBorder("TableHeader.cellBorder"));
    setHorizontalAlignment(CENTER);
    setForeground(header.getForeground());
    setBackground(header.getBackground());
    setFont(header.getFont());
  }

  @Override
  public Component getListCellRendererComponent(JList list, Object value,
      int index, boolean isSelected, boolean cellHasFocus) {
    setText((value == null) ? "" : value.toString());
    return this;
  }
}

public class RowHeaderTable extends JFrame {

  public RowHeaderTable() {
    super("Row Header Example");
    setSize(300, 150);

    ListModel lm = new AbstractListModel() {
      String headers[] = { "a", "b", "c", "d", "e", "f", "g", "h", "i" };

      @Override
      public int getSize() {
        return headers.length;
      }

      @Override
      public Object getElementAt(int index) {
        return headers[index];
      }
    };    

    DefaultTableModel dm = new DefaultTableModel(lm.getSize(), 15);
    JTable table = new JTable(dm);
    table.setAutoResizeMode(JTable.AUTO_RESIZE_OFF);

    JList rowHeader = new JList(lm);
    rowHeader.setFixedCellWidth(50);

    // ***************  CODE ADDED  *******************
    // Add a Mouse Motion Listener for the rowHeader JList.
    rowHeader.addMouseMotionListener(new MouseMotionListener() {
        @Override
        public void mouseDragged(MouseEvent e) {
            // Set the list cell width as mouse is dragged.
            rowHeader.setFixedCellWidth(e.getX());
      }

        @Override
        public void mouseMoved(MouseEvent e) {
            // If the mouse pointer is near the end region of the 
            // list cell then change the mouse cursor to a resize cursor.
            if ((e.getX()>= (rowHeader.getWidth() - 5)) && (e.getX()<= rowHeader.getWidth())) {
                rowHeader.setCursor(new Cursor(Cursor.E_RESIZE_CURSOR));
            } 
            // If the mouse pointer is not near the end region of a cell 
            // then change the pointer back to its default.
            else {
                rowHeader.setCursor(new Cursor(Cursor.DEFAULT_CURSOR));
            }
        }
    });
    // ***********************************************  

    rowHeader.setFixedCellHeight(table.getRowHeight()
        + table.getRowMargin());
    //  + table.getIntercellSpacing().height);
    rowHeader.setCellRenderer(new RowHeaderRenderer(table));

    JScrollPane scroll = new JScrollPane(table);
    scroll.setRowHeaderView(rowHeader);
    getContentPane().add(scroll, BorderLayout.CENTER);
  }

  public static void main(String[] args) {
      RowHeaderTable frame = new RowHeaderTable();
    frame.addWindowListener(new WindowAdapter() {
      @Override
      public void windowClosing(WindowEvent e) {
        System.exit(0);
      }
    });
    frame.setVisible(true);
  }
}

Dealing with the listener is easier than it seems! Thank you! — pedroabreu, Dec 12 '15 at 00:42

score 0 · Answer 2 · answered May 05 '22 at 17:37

For someone who just got here, you can try my solution from the other thread. It is a custom rowHeader that extends JComponent. I wrote the class because of the tremendous lags I experienced when I'm dragging or resizing a row outside of row header's boundary and I can't find any solution that can fix the lags.

Here's the link https://stackoverflow.com/a/72131124/14127279

How to resize JScrollPane rowHeader

2 Answers2