16.txt

电子工业出版社出版的《java2应用开发指南》配套光盘源代码

例程16-1
//CropImageDemo.java
import java.net.URL;
import java.applet.Applet;
import java.awt.*;
import java.awt.image.*;
public class CropImageDemo extends Applet 
{
 	private Image im;
	private Image cropped;
	public void init() {
		MediaTracker mt  = new MediaTracker(this);
		URL 		 url = getClass().getResource("pic.jpg");
		try 
		{
			im = createImage((ImageProducer)url.getContent());
			mt.addImage(im, 0);
			mt.waitForID(0);
		}
		catch(Exception e) 
		{ 
			e.printStackTrace(); 
		}	
		//创建图像过滤器（剪裁矩形是顶点是100,5，宽为100高为100）
		ImageFilter filter = new CropImageFilter(110,5,100,100);
		//图像过滤器源
		FilteredImageSource fis = new FilteredImageSource(im.getSource(), filter);
		//用图像过滤器源创建图像
		cropped = createImage(fis);	
	}	
	public void paint(Graphics g) 
	{
		//在坐标为（0,0）处绘制正常的图像
		g.drawImage(im,0,0,this);
		//绘制经过过滤的图像
	  	g.drawImage(cropped,im.getWidth(this)+20,0,this);
	}
}



例程16-2
//AnimatorDemo.java
import java.util.*;
import java.awt.*;
import java.applet.*;
import java.text.*;

public class AnimatorDemo extends Applet implements Runnable 
{
    Thread timer;                // 用于显示时钟的线程
    int lastxs, lastys, lastxm,
        lastym, lastxh, lastyh; 
    SimpleDateFormat formatter;  //格式化时间显示
    String lastdate;             // 保存当前时间的字符串
    Font clockFaceFont;          //设置显示时钟里面的数字的字体
    Date currentDate;            // 显示当前时间
    Color handColor;             // 用于显示时针、分针和表盘的颜色
    Color numberColor;           // 用于显示秒针和数字的颜色

    public void init() 
    {
        int x,y;
        lastxs = lastys = lastxm = lastym = lastxh = lastyh = 0;
        formatter = new SimpleDateFormat ("yyyy EEE MMM dd hh:mm:ss ");
        currentDate = new Date();
        lastdate = formatter.format(currentDate);
        clockFaceFont = new Font("Serif", Font.PLAIN, 14);
        handColor = Color.blue;
        numberColor = Color.darkGray;

        try {
            setBackground(new Color(Integer.parseInt(getParameter("bgcolor"),16)));
        } catch (Exception E) { }
        try {
            handColor = new Color(Integer.parseInt(getParameter("fgcolor1"),16));
        } catch (Exception E) { }
        try {
            numberColor = new Color(Integer.parseInt(getParameter("fgcolor2"),16));
        } catch (Exception E) { }
        resize(300,300);              // 设置时钟窗口大小
    }

    // 计算四分之一的圆弧
    public void plotpoints(int x0, int y0, int x, int y, Graphics g) 
    {
        g.drawLine(x0+x,y0+y,x0+x,y0+y);
        g.drawLine(x0+y,y0+x,x0+y,y0+x);
        g.drawLine(x0+y,y0-x,x0+y,y0-x);
        g.drawLine(x0+x,y0-y,x0+x,y0-y);
        g.drawLine(x0-x,y0-y,x0-x,y0-y);
        g.drawLine(x0-y,y0-x,x0-y,y0-x);
        g.drawLine(x0-y,y0+x,x0-y,y0+x);
        g.drawLine(x0-x,y0+y,x0-x,y0+y);
    }

    // 用Bresenham算法来画圆，其中(x0,y0)是圆的中心，r为圆半径
    public void circle(int x0, int y0, int r, Graphics g) 
    {
        int x,y;
        float d;
        x=0;
        y=r;
        d=5/4-r;
        plotpoints(x0,y0,x,y,g);
        while (y>x) {
            if (d<0) {
                d=d+2*x+3;
                x++;
            }
            else {
                d=d+2*(x-y)+5;
                x++;
                y--;
            }
            plotpoints(x0,y0,x,y,g);
        }
    }
    
    public void paint(Graphics g) 
    {
        int xh, yh, xm, ym, xs, ys, s = 0, m = 10, h = 10, xcenter, ycenter;
        String today;

        currentDate = new Date();
        SimpleDateFormat formatter = new SimpleDateFormat("s",Locale.getDefault());
        try {
            s = Integer.parseInt(formatter.format(currentDate));
        } catch (NumberFormatException n) {
            s = 0;
        }
        formatter.applyPattern("m");
        try {
            m = Integer.parseInt(formatter.format(currentDate));
        } catch (NumberFormatException n) {
            m = 10;
        }    
        formatter.applyPattern("h");
        try {
            h = Integer.parseInt(formatter.format(currentDate));
        } catch (NumberFormatException n) {
            h = 10;
        }
        formatter.applyPattern("EEE MMM dd HH:mm:ss yyyy");
        today = formatter.format(currentDate);
        //设置时钟的表盘的中心点为（80,55）
xcenter=80;
        ycenter=55;
    
    	// a= s* pi/2 - pi/2 (to switch 0,0 from 3:00 to 12:00)
    	// x = r(cos a) + xcenter, y = r(sin a) + ycenter
    
        xs = (int)(Math.cos(s * 3.14f/30 - 3.14f/2) * 45 + xcenter);
        ys = (int)(Math.sin(s * 3.14f/30 - 3.14f/2) * 45 + ycenter);
        xm = (int)(Math.cos(m * 3.14f/30 - 3.14f/2) * 40 + xcenter);
        ym = (int)(Math.sin(m * 3.14f/30 - 3.14f/2) * 40 + ycenter);
        xh = (int)(Math.cos((h*30 + m/2) * 3.14f/180 - 3.14f/2) * 30 + xcenter);
        yh = (int)(Math.sin((h*30 + m/2) * 3.14f/180 - 3.14f/2) * 30 + ycenter);
    
    	//画时钟最外面的圆盘其中心在（xcenter,ycenter）半径为50  
        g.setFont(clockFaceFont);
        g.setColor(handColor);
        circle(xcenter,ycenter,50,g);
		//画时钟表盘里的数字
        g.setColor(numberColor);
        g.drawString("9",xcenter-45,ycenter+3); 
        g.drawString("3",xcenter+40,ycenter+3);
        g.drawString("12",xcenter-5,ycenter-37);
        g.drawString("6",xcenter-3,ycenter+45);

    	// 如果必要的话抹去然后重画 
        g.setColor(getBackground());
        if (xs != lastxs || ys != lastys) {
            g.drawLine(xcenter, ycenter, lastxs, lastys);
            g.drawString(lastdate, 5, 125);
        }
        if (xm != lastxm || ym != lastym) {
            g.drawLine(xcenter, ycenter-1, lastxm, lastym);
            g.drawLine(xcenter-1, ycenter, lastxm, lastym); }
        if (xh != lastxh || yh != lastyh) {
            g.drawLine(xcenter, ycenter-1, lastxh, lastyh);
            g.drawLine(xcenter-1, ycenter, lastxh, lastyh); }
        g.setColor(numberColor);
        g.drawString("", 5, 125);
        g.drawString(today, 5, 125);    
        g.drawLine(xcenter, ycenter, xs, ys);
        g.setColor(handColor);
        g.drawLine(xcenter, ycenter-1, xm, ym);
        g.drawLine(xcenter-1, ycenter, xm, ym);
        g.drawLine(xcenter, ycenter-1, xh, yh);
        g.drawLine(xcenter-1, ycenter, xh, yh);
        lastxs=xs; lastys=ys;
        lastxm=xm; lastym=ym;
        lastxh=xh; lastyh=yh;
        lastdate = today;
        currentDate=null;
    }
	//applet的启动方法
    public void start() 
    {
        timer = new Thread(this);
        timer.start();
    }
	// applet的停止方法
    public void stop() 
    {
        timer = null;
    }
	//线程的run方法
    public void run() 
    {
        Thread me = Thread.currentThread();
        while (timer == me) {
            try {
                Thread.currentThread().sleep(1000);
            } 
            catch (InterruptedException e) {
            }
            repaint();
        }
    }
	//注意：这里重写了update()方法，只是调用了paint()方法来消除闪烁现象
    public void update(Graphics g) 
    {
        paint(g);
    }
}