shadowedreddot.java

Java程序设计(美) David D. Riley著 机械工业出版社 书籍配套 代码

// Figure 6.18

import java.awt.Color;
import javax.swing.JFrame;
/**	CLass Invariant
 *		A ShadowedRedDot object...
 *			is a filled circular region colored red 
 *			and is centered its Container 
 *			and has a shadow that is the same size as dot and colored black
 *			and the shadow is delta units left & above dot upon the window
 *					(delta is 10% of the diameter of dot) 
 */
public class ShadowedRedDot  {
	private Oval dot, shadow;

	/**	post:	dot.getWidth() == dot.getHeight() == 200   */
	public ShadowedRedDot(JFrame w )  {
		dot = new Oval(w.getWidth()/2-100, w.getHeight()/2-100, 200, 200);
		dot.setBackground( Color.red );
		shadow = new Oval(dot.getX()+20, dot.getY()-20, 200, 200);
		shadow.setBackground( Color.black );
		w.add(shadow, 0);
		w.add(dot, 0);
		w.repaint();
	}

	/**	post:	dot.getWidth() == dot.getWidth()@pre * (100 + d)/100
	 *			and dot.getHeight() == dot.getHeight()@pre * (100 + d)/100  
	 */
	public void zoom(double d)   {
		dot.setLocation( (int)(-d/200*dot.getWidth()) + dot.getX(), 
							(int)(-d/200*dot.getHeight()) + dot.getY() );
		dot.setSize( (int)(dot.getWidth() * (1.0+d/100)), 
						(int)(dot.getHeight() * (1.0+d/100)) );
		shadow.setSize( dot.getWidth(), dot.getHeight() );
		shadow.setLocation( dot.getX()+(int)(dot.getWidth()*0.1),
							   dot.getY()-(int)(dot.getHeight()*0.1) );
		dot.repaint();
		shadow.repaint();
	}

	/**	post:	dot.getWidth() == dot.getHeight == 200   */
	public void reset()   {
		int dotCenterX, dotCenterY;
		dotCenterX = dot.getX() + dot.getWidth()/2;
		dotCenterY = dot.getY() + dot.getHeight()/2;
		dot.setSize( 200, 200 );
		dot.setLocation( dotCenterX-100, dotCenterY-100 );
		shadow.setSize( 200, 200 );
		shadow.setLocation( dot.getX()+20, dot.getY()-20 );
		dot.repaint();
		shadow.repaint();
	}
}