Java基础之在窗口中绘图——绘制直线和矩形（Sketcher 2 drawing lines and rectangles）

控制台程序。

 import javax.swing.JComponent;
 import java.util.*;
 import java.awt.*;
 import java.awt.geom.*;

 @SuppressWarnings("serial")
 public class SketcherView extends JComponent implements Observer {
   public SketcherView(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...
   }

   // Method to draw on the view
   @Override
   public void paint(Graphics g) {
     // Temporary code...
     Graphics2D g2D = (Graphics2D)g;                                    // Get a Java 2D device context

     g2D.setPaint(Color.RED);                                           // Draw in red

     // Position width and height of first rectangle
     Point2D.Float p1 = new Point2D.Float(50.0f, 10.0f);
     float width1 = 60;
     float height1 = 80;

     // Create and draw the first rectangle
     Rectangle2D.Float rect = new Rectangle2D.Float(p1.x, p1.y, width1, height1);
     g2D.draw(rect);

     // Position width and height of second rectangle
     Point2D.Float p2 = new Point2D.Float(150.0f, 100.0f);
     float width2 = width1 + 30;
     float height2 = height1 + 40;

     // Create and draw the second rectangle
     g2D.draw(new Rectangle2D.Float(
                        (float)(p2.getX()), (float)(p2.getY()), width2, height2));
     g2D.setPaint(Color.BLUE);                                          // Draw in blue

     // Draw lines to join corresponding corners of the rectangles
     Line2D.Float line = new Line2D.Float(p1,p2);
     g2D.draw(line);

     p1.setLocation(p1.x + width1, p1.y);
     p2.setLocation(p2.x + width2, p2.y);
     g2D.draw(new Line2D.Float(p1,p2));

     p1.setLocation(p1.x, p1.y + height1);
     p2.setLocation(p2.x, p2.y + height2);
     g2D.draw(new Line2D.Float(p1,p2));

     p1.setLocation(p1.x - width1, p1.y);
     p2.setLocation(p2.x - width2, p2.y);
     g2D.draw(new Line2D.Float(p1, p2));

     g2D.drawString("Lines and rectangles", 60, 250);                   // Draw some text

   }

   private Sketcher theApp;                                             // The application object
 }

其他部分与上一例相同。