Java – how do we draw a line between two panels

I just want to connect the panel by drawing lines

I have two panels, both of which contain a JTable I want to connect each cell of a JTable of one panel to another JTable of another panel

Here, I want to draw lines like I highlighted with pink circles

This is the code snippet I used to create jtables

DefaultTableModel fcdbDataModel = new DefaultTableModel(fcdbIdTxnArray,fcdbIdTxnColumnArray);
fcdbIdTxnJTable = new FieldMapperJTable(fcdbDataModel);

Here, fieldmapperjtable is my custom JTable class

Solution

You can easily use JFrame / jdialog glasspane as the drawing field Just set the custom component as the glass pane of the frame, and then draw the link directly on it

You can also use the hierarchical pane of the frame / dialog box to do the same

This is a small working example of how to draw such a "link" on a glass pane component:

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.HashMap;
import java.util.Map;

/**
 * @see https://stackoverflow.com/a/12389479/909085
 */

public class ComponentLinkerTest extends JComponent
{
    private Map<JComponent,JComponent> linked;

    public ComponentLinkerTest ()
    {
        super ();
        linked = new HashMap<JComponent,JComponent> ();
    }

    public void link ( JComponent c1,JComponent c2 )
    {
        linked.put ( c1,c2 );
        repaint ();
    }

    protected void paintComponent ( Graphics g )
    {
        Graphics2D g2d = ( Graphics2D ) g;
        g2d.setRenderingHint ( RenderingHints.KEY_ANTIALIASING,RenderingHints.VALUE_ANTIALIAS_ON );

        g2d.setPaint ( Color.BLACK );
        for ( JComponent c1 : linked.keySet () )
        {
            Point p1 = getRectCenter ( getBoundsInWindow ( c1 ) );
            Point p2 = getRectCenter ( getBoundsInWindow ( linked.get ( c1 ) ) );
            g2d.drawLine ( p1.x,p1.y,p2.x,p2.y );
        }
    }

    private Point getRectCenter ( Rectangle rect )
    {
        return new Point ( rect.x + rect.width / 2,rect.y + rect.height / 2 );
    }

    private Rectangle getBoundsInWindow ( Component component )
    {
        return getRelativeBounds ( component,getRootPaneAncestor ( component ) );
    }

    private Rectangle getRelativeBounds ( Component component,Component relativeTo )
    {
        return new Rectangle ( getRelativeLocation ( component,relativeTo ),component.getSize () );
    }

    private Point getRelativeLocation ( Component component,Component relativeTo )
    {
        Point los = component.getLocationOnScreen ();
        Point rt = relativeTo.getLocationOnScreen ();
        return new Point ( los.x - rt.x,los.y - rt.y );
    }

    private JRootPane getRootPaneAncestor ( Component c )
    {
        for ( Container p = c.getParent (); p != null; p = p.getParent () )
        {
            if ( p instanceof JRootPane )
            {
                return ( JRootPane ) p;
            }
        }
        return null;
    }

    public boolean contains ( int x,int y )
    {
        return false;
    }

    private static ComponentLinkerTest linker;

    public static void main ( String[] args )
    {
        setupLookAndFeel ();

        JFrame frame = new JFrame ();

        linker = new ComponentLinkerTest ();
        frame.setGlassPane ( linker );
        linker.setVisible ( true );

        JPanel content = new JPanel ();
        content.setLayout ( new GridLayout ( 10,5,5 ) );
        content.setBorder ( BorderFactory.createEmptyBorder ( 5,5 ) );
        frame.add ( content );

        for ( int i = 0; i < 50; i++ )
        {
            final JButton button = new JButton ( "Button" + i );
            button.addActionListener ( new ActionListener ()
            {
                public void actionPerformed ( ActionEvent e )
                {
                    link ( button );
                }
            } );
            content.add ( button );
        }

        frame.setDefaultCloSEOperation ( JFrame.EXIT_ON_CLOSE );
        frame.pack ();
        frame.setLocationRelativeTo ( null );
        frame.setVisible ( true );
    }

    private static JButton last = null;

    private static void link ( JButton button )
    {
        if ( last == null )
        {
            last = button;
        }
        else
        {
            linker.link ( last,button );
            last = null;
        }
    }

    private static void setupLookAndFeel ()
    {
        try
        {
            UIManager.setLookAndFeel ( UIManager.getSystemLookAndFeelClassName () );
        }
        catch ( ClassNotFoundException e )
        {
            e.printStackTrace ();
        }
        catch ( InstantiationException e )
        {
            e.printStackTrace ();
        }
        catch ( illegalaccessexception e )
        {
            e.printStackTrace ();
        }
        catch ( UnsupportedLookAndFeelException e )
        {
            e.printStackTrace ();
        }
    }
}

The results are as follows: (just click any two buttons one by one, and they will be linked)

Attachment: to make the line thicker, you can change the stroke when painting:

g2d.setstroke ( new Basicstroke ( 5f ) );