driver.java

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

import java.awt.Color;

/**	Author: David D. Riley
 *		Date: Jan, 2005
 *   Histogram Program (Figure 5.27)
 */
	
public class Driver  extends  ThreeButtons{
	private ThreeButtonFrame  histoWin;
	private Rectangle leftBar, midBar, rightBar;
	private int leftClickCount, midClickCount, rightClickCount;
	private final int maxBarHeight = 400;

		/** post:	A window is displayed that contains a histogram of the
	 *			number of times that each window button is clicked
	 *			as a percentage of the total number of such clicks.  
	 */
	public Driver()   {
		histoWin = new ThreeButtonFrame("Button Click Histogram");
		histoWin.setLayout(null);
		leftClickCount = 0;
		midClickCount = 0;
		rightClickCount = 0;
		leftBar = newBar(100);
		histoWin.add(leftBar, 0);
		midBar = newBar(250);
		histoWin.add(midBar, 0);
		rightBar = newBar(400);
		histoWin.add(rightBar, 0);
		histoWin.repaint();
	}
	
	/** pre:	leftBar, midBar and rightBar are constructed
 	 *	post:	leftClickCount == leftClickCount@pre + 1
 	 *			and all bars of the histogram are properly updated  
	 */
	public  void  leftAction()   {
		leftClickCount++;
		redrawHistogram();
	}

	/**	pre:	leftBar, midBar and rightBar are constructed
	 *	post:	midClickCount == midClickCount@pre + 1
 	 *			and all bars of the histogram are properly updated  
	 */
	public  void  midAction()   {
		midClickCount++;
		redrawHistogram();
	}
	
	/**	pre:	leftBar, midBar and rightBar are constructed
	 *	post:	rightClickCount == rightClickCount@pre + 1
 	 *			and all bars of the histogram are properly updated  
	 */
	public  void  rightAction()   {
		rightClickCount++;
		redrawHistogram();
	}
	
	/**	post:	result is a filled blue rectangle 
	 *			and  result.getWidth() == 100  and  result.getX() == j 
	 */
	private Rectangle newBar(int j)   {
		Rectangle tmp = new Rectangle(j, 0, 100, 0);
		tmp.setBackground(Color.blue);
		return tmp;
	}
	
	/**	pre:	leftBar, midBar and rightBar are constructed
	 *	post:	all bars of the histogram are properly updated 
	 */
	private void redrawHistogram()   {
		redrawOneBar(leftBar, leftClickCount);
		redrawOneBar(midBar, midClickCount);
		redrawOneBar(rightBar, rightClickCount);
	}
	
	/**	pre:	r is constructed
	 *	post:	the y and height attributes of r are adjusted to a new height of
 	 *			maxBarHeight * (c/(leftClickCount+midClickCount+rightClickCount)) 
	 */
	private void redrawOneBar(Rectangle r, int c)   {
		int totalClicks, newHeight;
		totalClicks = leftClickCount + midClickCount + rightClickCount;
		newHeight = (int)((double)c / totalClicks * maxBarHeight);
		r.setLocation( r.getX(), 430-newHeight );
		r.setSize( r.getWidth(), newHeight );
		r.repaint();
	}		
}