How to make lines in GridLayout?

Question

I use GridLayout with 2 columns and many rows. I want to draw a line between the two columns. How can I do this in GridLayout?

Answer 1

tjacobs01 wrote:
overridding paintComponent probably won't work, because the children will paint over it. Not if the opaque has been set. Also, I wonder if the "gaps" will show through even if the children keep opaque true.
Yep, you can do this by setting the background color of the panel to the column line color you desired, and let this color "shine through" the gaps in the grid layout:
import java.awt.Color;
import java.awt.Font;
import java.awt.GridLayout;
import javax.swing.BorderFactory;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JComponent;
import javax.swing.SwingConstants;
public class GridsShowQuestion
  private static final int GAP = 10;
  private static final int ROWS = 3;
  private static final int COLS = ROWS;
  private static final int FONT_SIZE = 50;
  private JPanel mainPanel = new JPanel();
  public GridsShowQuestion()
    mainPanel.setBackground(Color.red);
    mainPanel.setLayout(new GridLayout(ROWS, COLS, GAP, 0));
    for (int i = 0; i < ROWS; i++)
      for (int j = 0; j < COLS; j++)
        JLabel lbl = new JLabel("X");
        lbl.setFont(new Font(Font.DIALOG, Font.BOLD, FONT_SIZE));
        int eb = 10;
        lbl.setBorder(BorderFactory.createEmptyBorder(eb, 3*eb, eb, 3*eb));
        lbl.setHorizontalAlignment(SwingConstants.CENTER);
        lbl.setOpaque(true);
        mainPanel.add(lbl);
  public JComponent getComponent()
    return mainPanel;
  private static void createAndShowUI()
    JFrame frame = new JFrame("GridsShowQuestion");
    frame.getContentPane().add(new GridsShowQuestion().getComponent());
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.pack();
    frame.setLocationRelativeTo(null);
    frame.setVisible(true);
  public static void main(String[] args)
    java.awt.EventQueue.invokeLater(new Runnable()
      public void run()
        createAndShowUI();
}Edited by: Encephalopathic on Oct 14, 2008 7:16 PM