sketchview.java

Java Classic Examples是我买的两本书：《JAVA经典实例》和《java入门经典源代码》里边附送光盘里带的源码

import javax.swing.*;
import java.util.*;                  // For Observer
import java.awt.*;                   // For Graphics
import java.awt.geom.*;

class SketchView extends JComponent
                 implements Observer
{
  public void paint(Graphics g)
  {
    // Temporary code
    Graphics2D g2D = (Graphics2D)g;                 // Get a Java 2D device context

    Point2D.Double position = new Point2D.Double(50,10);  // Initial position
    double width = 150;                                   // Width of ellipse
    double height = 100;                                  // Height of ellipse
    double start = 30;                                    // Start angle for arc
    double extent = 120;                                  // Extent of arc
    double diameter = 40;                                 // Diameter of circle

    // Define open arc as an upper segment of an ellipse
    Arc2D.Double top = new Arc2D.Double(position.x, position.y,
                                      width, height,
                                      start, extent,
                                      Arc2D.OPEN);

    // Define open arc as lower segment of ellipse shifted up relative to 1st
    Arc2D.Double bottom = new Arc2D.Double(
                                      position.x, position.y - height + diameter,
                                      width, height,
                                      start + 180, extent,
                                      Arc2D.OPEN);
                                        
    // Create a circle centered between the two arcs
    Ellipse2D.Double circle1 = new Ellipse2D.Double(
                                      position.x + width/2 - diameter/2,position.y,
                                      diameter, diameter);

    // Create a second circle concentric with the first and half the diameter
    Ellipse2D.Double circle2 = new Ellipse2D.Double(
                   position.x + width/2 - diameter/4, position.y + diameter/4,
                   diameter/2, diameter/2);

    // Draw all the shapes
    g2D.setPaint(Color.black);                       // Draw in black
    g2D.draw(top);
    g2D.draw(bottom);

    g2D.setPaint(Color.blue);                        // Draw in blue
    g2D.draw(circle1);
    g2D.draw(circle2);
    g2D.drawString("Arcs and ellipses", 80, 100);    // Draw some text
  }

  public SketchView(Sketcher theApp)
  {
    this.theApp = theApp;
  }

  // Method called by Observable object when it changes
  public void update(Observable o, Object rectangle)
  {
    // Code to respond to changes in the model...
  }

  private Sketcher theApp;           // The application object
}