Swing基础（三）——2D绘图

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

/**
 * @version 1.32 2007-04-14
 * @author Cay Horstmann
 */
public class DrawTest
{
   public static void main(String[] args)
   {	//事件调度线程
      EventQueue.invokeLater(new Runnable()
         {	@Override
            public void run()
         {		//创建一个窗体
               DrawFrame frame = new DrawFrame();
               //设置窗体默认关闭操作为退出程序
               frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
               	//设置窗体为可见
               frame.setVisible(true);
            }
         });
   }
}

/**
 * A frame that contains a panel with drawings
 */
class DrawFrame extends JFrame
{
   public DrawFrame()
   {
	   //设置窗体标题
      setTitle("DrawTest");
      //设置窗体大小
      setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);
      // add panel to frame
      DrawComponent component = new DrawComponent();
      add(component);
   }

   public static final int DEFAULT_WIDTH = 400;
   public static final int DEFAULT_HEIGHT = 400;
}
/**
 * A component that displays rectangles and ellipses.
 */
class DrawComponent extends JComponent
{
   public void paintComponent(Graphics g)
   {
      Graphics2D g2 = (Graphics2D) g;
      // draw a rectangle
      double leftX = 100;
      double topY = 100;
      double width = 200;
      double height = 150;

      Rectangle2D rect = new Rectangle2D.Double(leftX, topY, width, height);
      g2.draw(rect);

      // draw the enclosed ellipse
      
      Ellipse2D ellipse = new Ellipse2D.Double();
      ellipse.setFrame(rect);
      g2.draw(ellipse);

      // draw a diagonal line

      g2.draw(new Line2D.Double(leftX, topY, leftX + width, topY + height));

      // draw a circle with the same center
     //获得rect的中心坐标
      double centerX = rect.getCenterX();
      double centerY = rect.getCenterY();
      double radius = 150;

      Ellipse2D circle = new Ellipse2D.Double();
      circle.setFrameFromCenter(centerX, centerY, centerX + radius, centerY + radius);
      g2.draw(circle);
   }
}