import java.util.*;

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

import javax.swing.event.*;

/**

* Note: Normally the ButtonPanel and DrawingArea would not be static classes.

* This was done for the convenience of posting the code in one class and to

* highlight the differences between the two approaches. All the differences

* are found in the DrawingArea class.

*/

public class DrawOnComponent

{

public static void main(String[] args)

{

SwingUtilities.invokeLater(new Runnable() {

public void run() {

createAndShowGUI();

}

});

}

private static void createAndShowGUI()

{

DrawingArea drawingArea = new DrawingArea();

drawingArea.addRectangle(new Rectangle(10, 10, 200, 100), Color.RED);

drawingArea.addRectangle(new Rectangle(210, 110, 20, 100), Color.BLUE);

ButtonPanel buttonPanel = new ButtonPanel( drawingArea );

JFrame.setDefaultLookAndFeelDecorated(true);

JFrame frame = new JFrame("Draw On Component");

frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );

frame.getContentPane().add(drawingArea);

frame.getContentPane().add(buttonPanel, BorderLayout.SOUTH);

frame.setSize(400, 400);

frame.setLocationRelativeTo( null );

frame.setVisible(true);

}

static class ButtonPanel extends JPanel implements ActionListener

{

private DrawingArea drawingArea;

public ButtonPanel(DrawingArea drawingArea)

{

this.drawingArea = drawingArea;

add( createButton(" ", Color.BLACK) );

add( createButton(" ", Color.RED) );

add( createButton(" ", Color.GREEN) );

add( createButton(" ", Color.BLUE) );

add( createButton(" ", Color.ORANGE) );

add( createButton(" ", Color.YELLOW) );

add( createButton("Clear Drawing", null) );

}

private JButton createButton(String text, Color background)

{

JButton button = new JButton( text );

button.setBackground( background );

button.addActionListener( this );

return button;

}

public void actionPerformed(ActionEvent e)

{

JButton button = (JButton)e.getSource();

if ("Clear Drawing".equals(e.getActionCommand()))

drawingArea.clear();

else

drawingArea.setForeground( button.getBackground() );

}

}

static class DrawingArea extends JPanel

{

private final static int AREA_SIZE = 400;

private ArrayList<ColoredRectangle> coloredRectangles = new ArrayList<ColoredRectangle>();

private Rectangle shape;

public DrawingArea()

{

setBackground(Color.WHITE);

MyMouseListener ml = new MyMouseListener();

addMouseListener(ml);

addMouseMotionListener(ml);

}

@Override

public Dimension getPreferredSize()

{

return isPreferredSizeSet() ?

super.getPreferredSize() : new Dimension(AREA_SIZE, AREA_SIZE);

}

@Override

protected void paintComponent(Graphics g)

{

super.paintComponent(g);

// Custom code to paint all the Rectangles from the List

Graphics2D g2d = (Graphics2D)g;

Color foreground = g2d.getColor();

g2d.setColor( Color.BLACK );

g2d.drawString("Add a rectangle by doing mouse press, drag and release!", 40, 15);

for (DrawingArea.ColoredRectangle cr : coloredRectangles)

{

g2d.setColor( cr.getForeground() );

g2d.draw( cr.getRectangle() );

}

// Paint the Rectangle as the mouse is being dragged

if (shape != null)

{

g2d.setColor( foreground );

g2d.draw( shape );

}

}

public void addRectangle(Rectangle rectangle, Color color)

{

// Add the Rectangle to the List so it can be repainted

ColoredRectangle cr = new ColoredRectangle(color, rectangle);

coloredRectangles.add( cr );

repaint();

}

public void clear()

{

coloredRectangles.clear();

repaint();

}

class MyMouseListener extends MouseInputAdapter

{

private Point startPoint;

public void mousePressed(MouseEvent e)

{

startPoint = e.getPoint();

shape = new Rectangle();

}

public void mouseDragged(MouseEvent e)

{

int x = Math.min(startPoint.x, e.getX());

int y = Math.min(startPoint.y, e.getY());

int width = Math.abs(startPoint.x - e.getX());

int height = Math.abs(startPoint.y - e.getY());

shape.setBounds(x, y, width, height);

repaint();

}

public void mouseReleased(MouseEvent e)

{

if (shape.width != 0 || shape.height != 0)

{

addRectangle(shape, e.getComponent().getForeground());

}

shape = null;

}

}

class ColoredRectangle

{

private Color foreground;

private Rectangle rectangle;

public ColoredRectangle(Color foreground, Rectangle rectangle)

{

this.foreground = foreground;

this.rectangle = rectangle;

}

public Color getForeground()

{

return foreground;

}

public void setForeground(Color foreground)

{

this.foreground = foreground;

}

public Rectangle getRectangle()

{

return rectangle;

}

}

}

}