Draw Connecting Lines Between Swing Components

How can I write a line connecting two swing components ?

One way is to draw the line on the parent container.

These swing components are inside of a scrolled component, How to keep track of the lines position ?

Let the components keep track of things.

import java.awt.*;

import java.awt.geom.*;

import java.text.NumberFormat;

import javax.swing.*;

public class ConnectingLine

{

NumberFormat nf;

public ConnectingLine()

{

nf = NumberFormat.getInstance();

nf.setMinimumIntegerDigits(2);

}

private JPanel getContent()

{

JPanel panel = new JPanel(new GridBagLayout());

GridBagConstraints gbc = new GridBagConstraints();

gbc.insets = new Insets(20,0,20,0);

gbc.weightx = 1.0;

gbc.fill = GridBagConstraints.HORIZONTAL;

gbc.gridwidth = GridBagConstraints.REMAINDER;

for(int j = 0, k = 1; j < 5; j++, k+=2)

panel.add(getPanel(k), gbc);

return panel;

}

private JPanel getPanel(int n)

{

ConnectingPanel panel = new ConnectingPanel();

panel.setLayout(new GridBagLayout());

GridBagConstraints gbc = new GridBagConstraints();

gbc.insets = new Insets(5,5,5,5);

gbc.weightx = 1.0;

panel.add(getChild("column_", n), gbc);

panel.add(getChild("dest_", n), gbc);

return panel;

}

private JPanel getChild(String s, int n)

{

JPanel panel = new JPanel(new GridBagLayout());

GridBagConstraints gbc = new GridBagConstraints();

gbc.weightx = 1.0;

gbc.weighty = 1.0;

gbc.fill = GridBagConstraints.BOTH;

gbc.gridwidth = GridBagConstraints.REMAINDER;

panel.setOpaque(false); // no tricks

panel.setPreferredSize(new Dimension(125, 75));

panel.setBorder(BorderFactory.createEtchedBorder());

panel.add(new JLabel(s + nf.format(n), JLabel.CENTER), gbc);

gbc.weighty = 0.0;

panel.add(new JSeparator(), gbc);

gbc.weighty = 1.0;

panel.add(new JLabel(s + nf.format(n+1), JLabel.CENTER), gbc);

return panel;

}

public static void main(String[] args)

{

JFrame f = new JFrame();

f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

f.setContentPane(new JScrollPane(new ConnectingLine().getContent()));

f.setSize(500,400);

f.setLocation(200,200);

f.setVisible(true);

}

}

class ConnectingPanel extends JPanel

{

final int HI = 0;// top JLabel

// JSeparator is middle component

final int LO = 2;// bottom JLabel

protected void paintComponent(Graphics g)

{

super.paintComponent(g);

Graphics2D g2 = (Graphics2D)g;

g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,

RenderingHints.VALUE_ANTIALIAS_ON);

g2.setPaint(Color.blue);

Component[] c = getComponents();

for(int j = 0; j < c.length; j++)

{

for(int k = j+1; k < c.length; k++)

{

Point p1 = //getPointForParent(c[j], c[k]);

getPointForChild(c[j], c[k], HI);

Point p2 = //getPointForParent(c[k], c[j]);

getPointForChild(c[k], c[j], HI);

g2.draw(new Line2D.Double(p1, p2));

}

}

}

/** middle of parent JPanel that contains the two JLabels */

private Point getPointForParent(Component c1, Component c2)

{

Rectangle r1 = c1.getBounds();

Rectangle r2 = c2.getBounds();

Point p = new Point();

int outcode = r1.outcode(r2.getCenterX(), r2.getCenterY());

switch(outcode)

{

case Rectangle2D.OUT_TOP:

break;

case Rectangle2D.OUT_LEFT:

p.x = r1.x;

p.y = r1.y + r1.height/2 -1;

break;

case Rectangle2D.OUT_BOTTOM:

break;

case Rectangle2D.OUT_RIGHT:

p.x = r1.x + r1.width -1;

p.y = r1.y + r1.height/2 -1;

break;

default:

System.out.println("outcode for center or corners " + outcode);

}

return p;

}

/** center of top (or bottom) JLabel - as shown in ascii art above */

private Point getPointForChild(Component c1, Component c2, int index)

{

Rectangle r1 = c1.getBounds();

Point cp = getCenter(c1, index);

Rectangle r2 = c2.getBounds();

Point p = new Point();

int outcode = r1.outcode(r2.getCenterX(), r2.getCenterY());

switch(outcode)

{

case Rectangle2D.OUT_TOP:

break;

case Rectangle2D.OUT_LEFT:

p.x = r1.x;

p.y = cp.y;

break;

case Rectangle2D.OUT_BOTTOM:

break;

case Rectangle2D.OUT_RIGHT:

p.x = r1.x + r1.width -1;

p.y = cp.y;

break;

default:

System.out.println("outcode for center or corners " + outcode);

}

return p;

}

private Point getCenter(Component parent, int childIndex)

{

Component child = ((Container)parent).getComponent(childIndex);

Rectangle r = child.getBounds();

Rectangle parentBounds = parent.getBounds();

Point p = new Point();

p.x = parentBounds.width/2;

p.y = parentBounds.y + r.y + r.height/2;

return p;

}

}

74philipa at 2007-7-14 1:06:00 >