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Java2D: An Introduction and Tutorial

2. Drawing Shapes in Java2D

2.1 Drawing Shapes: Overview

public void paintComponent(Graphics g) {
  super.paintComponent(g);
  Graphics2D g2d = (Graphics2D)g;
  // Assume x, y, and diameter are instance variables
  Ellipse2D.Double circle =
    new Ellipse2D.double(x, y, diameter, diameter);
  g2d.fill(circle);
  ...
}

2.2 Shape Classes

• Arc2D.Double, Arc2D.Float
• Area
• CubicCurve2D.Double, CubicCurve2D.Float
• Ellipse2D.Double, Ellipse2D.Float
• GeneralPath
• Line2D.Double, Line2D.Float
• Polygon
• QuadCurve2D.Double, QuadCurve2D.Float
• Rectangle2D.Double, Rectangle2D.Float, Rectangle
• RoundRectangle2D.Double, RoundRectangle2D.Float

2.3 Drawing Shapes: Example Code

ShapeExample.java

import com.sun.java.swing.*; // For JPanel, etc.
import java.awt.*;           // For Graphics, etc.
import java.awt.geom.*;      // For Ellipse2D, etc.

/** An example of drawing/filling shapes with Java2D in Java 1.2.
 *  1998 Marty Hall, http://www.apl.jhu.edu/~hall/java/
 */

public class ShapeExample extends JPanel {
  private Ellipse2D.Double circle =
    new Ellipse2D.Double(10, 10, 350, 350);
  private Rectangle2D.Double square =
    new Rectangle2D.Double(10, 10, 350, 350);

  public void paintComponent(Graphics g) {
    clear(g);
    Graphics2D g2d = (Graphics2D)g;
    g2d.fill(circle);
    g2d.draw(square);
  }

  // super.paintComponent clears offscreen pixmap,
  // since we're using double buffering by default.

  protected void clear(Graphics g) {
    super.paintComponent(g);
  }

  protected Ellipse2D.Double getCircle() {
    return(circle);
  }

  public static void main(String[] args) {
    WindowUtilities.openInJFrame(new ShapeExample(), 380, 400);
  }
}

WindowUtilities.java

import com.sun.java.swing.*;
import java.awt.*;

/** A few utilities that simplify testing of windows in Swing.
 *  1998 Marty Hall, http://www.apl.jhu.edu/~hall/java/
 */

public class WindowUtilities {

  /** A simplified way to see a JPanel or other Container.
   *  Pops up a JFrame with specified Container as the content pane.
   */

  public static JFrame openInJFrame(Container content,
                                    int width,
                                    int height,
                                    String title,
                                    Color bgColor) {
    JFrame frame = new JFrame(title);
    frame.setBackground(bgColor);
    content.setBackground(bgColor);
    frame.setSize(width, height);
    frame.setContentPane(content);
    frame.addWindowListener(new ExitListener());
    frame.setVisible(true);
    return(frame);
  }

  /** Uses Color.white as the background color. */

  public static JFrame openInJFrame(Container content,
                                    int width,
                                    int height,
                                    String title) {
    return(openInJFrame(content, width, height, title, Color.white));
  }

  /** Uses Color.white as the background color, and the
   *  name of the Container's class as the JFrame title.
   */

  public static JFrame openInJFrame(Container content,
                                    int width,
                                    int height) {
    return(openInJFrame(content, width, height,
                        content.getClass().getName(),
                        Color.white));
  }
}

ExitListener.java

import java.awt.*;
import java.awt.event.*;

/** A listener that you attach to the top-level Frame or JFrame of
 *  your application, so quitting the frame exits the application.
 *  1998 Marty Hall, http://www.apl.jhu.edu/~hall/java/
 */

public class ExitListener extends WindowAdapter {
  public void windowClosing(WindowEvent event) {
    System.exit(0);
  }
}

2.4 Drawing Shapes: Example Output

[Move on to the next part of the article]

This article first appeared in November, 1998

Copyright 1998 Mecklermedia Corporation.
All Rights Reserved. Legal Notices.