Question

、编写Applet程序，在屏幕上画一组同心圆（至少20个），相邻两圆的直径相差10 像素。

用java Applet 运行！

Answer 1

public class MyClock extends Applet implements Runnable
{
static final int BACKGROUND=0; //背景图片的序号，供数组使用
static final int LOGO=1; //LOGO图片的序号，供数组使用
static final String JAVEX="bear"; //表盘上显示的文字
static final double MINSEC=0.104719755; //分针和秒针在表盘上的刻度（60个）间的弧度
static final double HOUR=0.523598776; //时针在表盘上的刻度（24个）间的弧度

Thread clockThread = null; //使用多线程机制，用另一个线程不断显示图片

//提供的默认参数，如果HTML文件里面没有给参数就使用
int width = 100;
int height = 100;
Color bgColor = new Color(0,0,0);
Color faceColor = new Color(0,0,0);
Color sweepColor = new Color(255,0,0);
Color minuteColor = new Color (192,192,192);
Color hourColor = new Color (255,255,255);
Color textColor = new Color (255,255,255);
Color caseColor = new Color (0,0,0);
Color trimColor = new Color (192,192,192);
String logoString=null;

Image images[] = new Image[2]; //背景和LOGO的图片

boolean isPainted=false; //如果第一次载入时绘制背景及表盘，其他时候重绘则只绘制指针

//时钟圆心的位置
int x1,y1;

//最上面那个三角形的刻度图形的坐标
int xPoints[]=new int[3], yPoints[]=new int[3];

//保存当前时间，转换成(double)(hours + minutes/60)
Hms cur_time;

//秒针、分针、时针
SweepHand sweep;
HmHand minuteHand,
hourHand;

//用于绘制的时、分、秒
double lastHour;
int lastMinute,lastSecond;

//显示日期和表盘上的字母的字体
Font font;

//图片显示使用了缓冲机制，offScrImage和offScrGC存放缓冲区内图片的信息
Image offScrImage;
Graphics offScrGC;

//用于测试背景图片和LOGO图片
MediaTracker tracker;

int minDimension; // 如果背景区域不是正方形的话，保证时钟在中间显示
int originX; // 时钟图形所在正方形区域的左上角X坐标
int originY; // 时钟图形所在正方形区域的左上角Y坐标

double tzDifference=0; //时区间的差，向西为负数，向东为正数

boolean localOnly=false; //是否只使用本地时间，如果为FALSE则可以根据传入的时区显示该时区时间

//保存参数的类型说明
public String[][] getParameterInfo()
{
String[][] info = {
{"width", "int", "APPLET的长度，以象素为单位"},
{"height", "int", "APPLET的宽度，以象素为单位"},
{"bgColor", "string", "背景颜色，e.g FF0000"},
{"faceColor", "string", "表盘颜色"},
{"sweepColor", "string", "秒针颜色"},
{"minuteColor", "string", "分针颜色"},
{"hourColor", "string", "时针颜色"},
{"textColor", "string", "文本颜色"},
{"caseColor", "string", "框内颜色"},
{"trimColor", "string", "空白区颜色"},
{"bgImageURL", "string", "背景图片地址"},
{"logoString", "string", "LOGO字符"},
{"logoImageURL","string", "LOGO图片地址"},
{"timezone", "real", "时区间的差"},
{"localonly", "int", "是否考虑到时区差别"}
};
return info;
}

//显示信息
public String getAppletInfo()
{
return "版权所有，COPY必究，保护正版，人人有责";
}

void showURLerror(Exception e)
{
String errorMsg = "URL错误："+e;
showStatus(errorMsg);
System.err.println(errorMsg);
}

//相当于把时钟变成100×100的大小，percent即相对坐标
private int size(int percent)
{
return (int)((double)percent/100.0 * (double)minDimension);
}

public void init()
{
URL imagesURL[] = new URL[2];
String szImagesURL[] = new String[2];
tracker = new MediaTracker(this);

//得到HTML页面提供的参数，并把它转换相应的格式
String paramString = getParameter( "WIDTH" );
if( paramString != null )
width = Integer.valueOf(paramString).intValue();

paramString = getParameter( "HEIGHT" );
if( paramString != null )
height = Integer.valueOf(paramString).intValue();

paramString = getParameter( "TIMEZONE" );
if( paramString != null )
tzDifference = Double.valueOf(paramString).doubleValue();

paramString = getParameter( "LOCALONLY" );
if( paramString != null && Integer.valueOf(paramString).intValue() != 0){
localOnly=true;
tzDifference=0.;
}

paramString = getParameter( "BGCOLOR");
if( paramString != null )
bgColor=parseColorString(paramString);

paramString = getParameter( "FACECOLOR");
if( paramString != null )
faceColor=parseColorString(paramString);

paramString = getParameter( "SWEEPCOLOR");
if( paramString != null )
sweepColor=parseColorString(paramString);

paramString = getParameter( "MINUTECOLOR");
if( paramString != null )
minuteColor=parseColorString(paramString);

paramString = getParameter( "HOURCOLOR");
if( paramString != null )
hourColor=parseColorString(paramString);

paramString = getParameter( "TEXTCOLOR");
if( paramString != null )
textColor=parseColorString(paramString);

paramString = getParameter( "CASECOLOR");
if( paramString != null )
caseColor=parseColorString(paramString);

paramString = getParameter( "TRIMCOLOR");
if( paramString != null )
trimColor=parseColorString(paramString);

logoString = getParameter( "LOGOSTRING");
if( logoString == null )
logoString=JAVEX;
else if(logoString.length() > 8)
logoString= logoString.substring(0,8); //限制8个字母，否则显示不下!

//szImagesURL数组根据HTML传入参数存放图片的文件名
szImagesURL[BACKGROUND] = getParameter("BGIMAGEURL");
szImagesURL[LOGO] = getParameter("LOGOIMAGEURL");

//测试图片
for(int i=0; i<2; i++){
if(szImagesURL[i] != null){
//根据CodeBase参数与Image文件名得到image的路径，测试是否存在，如果不存在就不用图片
try{
imagesURL[i]=new URL(getCodeBase(),szImagesURL[i]);
} catch (MalformedURLException e)
{
showURLerror(e);
imagesURL[i]=null;
images[i]=null;
}
if(imagesURL[i] != null){
showStatus("加载图片: " + imagesURL[i].toString());
images[i]=getImage(imagesURL[i]);
if(images[i] != null)
tracker.addImage(images[i],i);
showStatus("");
}
try{
tracker.waitForAll(i);
}catch (InterruptedException e){}
}
else images[i]=null;
}

//得到相应时区的时间
cur_time=(localOnly)? new Hms() : new Hms(tzDifference);
lastHour=-1.0;
lastMinute=-1;
lastSecond=-1;

x1=width/2;
y1=height/2;

//换算出圆形时钟在背景里的左上角坐标
minDimension= Math.min(width, height);
originX=(width-minDimension)/2;
originY=(height-minDimension)/2;

//计算出上面三角形的三个点的坐标
xPoints[1]=x1-size(3); xPoints[2]=x1+size(3); xPoints[0]=x1;
yPoints[1]=y1-size(38);yPoints[2]=y1-size(38); yPoints[0]=y1-size(27);

//计算出秒针、分针、时针图形的各个点坐标
sweep=new SweepHand(x1,y1,size(40),3);
minuteHand=new HmHand(x1,y1,size(40),size(6),6);
hourHand=new HmHand(x1,y1,size(25),size(8),6);

//构造字体
font=new Font("TXT",Font.BOLD,size(10));

//构造缓冲区内图形
offScrImage = createImage(width,height);
offScrGC = offScrImage.getGraphics();

System.out.println(getAppletInfo());
}

public void start() //开始启动显示线程
{
if(clockThread == null){
clockThread = new Thread(this);
}
clockThread.start();
}

public void stop() //停止显示
{
clockThread = null;
}

private void drawHands(Graphics g)
{

double angle;
int i,j;
int x,y;

angle=MINSEC * lastSecond; //根据lastSecond算出秒针相对于12点刻度的角度
sweep.draw(faceColor, angle, g);//画出秒针

//如果时与分改变则重绘时针分针
if(cur_time.getMinutes() != lastMinute){
minuteHand.draw(faceColor,MINSEC*lastMinute,g);
if(cur_time.get_hours() != lastHour)
hourHand.draw(faceColor,HOUR*lastHour,g);
}

g.setColor(textColor);
g.fillRect(originX+size(12),y1-size(2),size(10),size(4)); //绘制左侧横条
g.fillRect(x1-size(2),originY + minDimension-size(22),size(4),size(10)); //绘制下面的横条
g.fillPolygon( xPoints, yPoints, 3); //绘制顶部的三角形
for(i=1;i<12;i+=3) //在表盘的2、3、5、6、8、9、11时针刻度区绘制圆
for(j=i;j<i+2;j++){
x=(int)(x1+Math.sin(HOUR*j)*size(35));
y=(int)(y1-Math.cos(HOUR*j)*size(35));
g.fillOval(x-size(3),y-size(3),size(6),size(6));
}

//设置字体
g.setFont(font);
FontMetrics fm=g.getFontMetrics();

//画顶部的LOGO字符串
g.drawString(logoString,x1-fm.stringWidth(logoString)/2,y1-size(12));

//得到日期
String day=Integer.toString(cur_time.getDate(),10);

//将日期绘制在表盘右侧
g.drawString( day,
originX + minDimension-size(14)-fm.stringWidth(day),
y1+size(5));

//外面画上框子
g.drawRect( originX + minDimension-size(14)-fm.stringWidth(day)-size(2),
y1-size(5)-size(2),
fm.stringWidth(day)+size(4),
size(10)+size(4));

if(images[LOGO] != null){ //如果LOGO图片存在，在底部画出来
x = originX + (minDimension-images[LOGO].getWidth(this))/2;
y = y1 + (minDimension/2 - size(22) - images[LOGO].getHeight(this))/2;
if(x > 0 && y > 0)
offScrGC.drawImage(images[LOGO], x, y, this);
}

lastHour=cur_time.get_hours();
hourHand.draw(hourColor,HOUR*lastHour,g); //画时针

lastMinute=cur_time.getMinutes();
minuteHand.draw(minuteColor,MINSEC*lastMinute,g); //画分针

g.setColor(minuteColor); //绘制分针尾部的圆形
g.fillOval(x1-size(4),y1-size(4),size(8),size(8));
g.setColor(sweepColor); //绘制秒针尾部的圆形
g.fillOval(x1-size(3),y1-size(3),size(6),size(6));

lastSecond=cur_time.getSeconds(); //得到新的秒数，重画
angle=MINSEC*lastSecond;
sweep.draw(sweepColor, angle,g);

g.setColor(trimColor);
g.fillOval(x1-size(1),y1-size(1),size(2),size(2)); //秒针尾部圆心部分应该是螺丝，挖空处理^_^
}

private Color parseColorString(String colorString) //参数传入为字符串形（规定为16进制6位字符串）
{
if(colorString.length()==6){
int R = Integer.valueOf(colorString.substring(0,2),16).intValue(); //前两位为R值
int G = Integer.valueOf(colorString.substring(2,4),16).intValue(); //中间为G值
int B = Integer.valueOf(colorString.substring(4,6),16).intValue(); //最后为B值
return new Color(R,G,B); //得到COLOR
}
else return Color.lightGray; //字符串不符合规范，默认为灰色
}

public void run()
{
repaint(); //每次启动时首先重绘一次
//每隔500ms获得现在时间并重绘一次
while(null != clockThread){
cur_time= (localOnly)? new Hms() :new Hms(tzDifference);
repaint();

try{
Thread.sleep(500);
} catch (InterruptedException e) {}
}
}

public void paint(Graphics g) //首先绘制缓冲区内图片，再显示出来
{
int i,x0,y0,x2,y2;

//如果没有提供背景图片，则用bgColor绘制背景
if(images[BACKGROUND] == null){
offScrGC.setColor(bgColor);
offScrGC.fillRect(0,0,width,height);
}
else //否则直接使用背景图片
offScrGC.drawImage(images[BACKGROUND], 0, 0, this);

//绘制外框到表盘间的部分
offScrGC.setColor(caseColor);

//将园形的范围适量缩减（不充满整个区域），防止有些地方被截取
offScrGC.fillOval( originX+1,
originY+1,
minDimension-2,
minDimension-2);

//绘制表盘
offScrGC.setColor(faceColor);
offScrGC.fillOval( originX + size(5),
originY + size(5),
minDimension - size(10),
minDimension - size(10));

//绘制外框线
offScrGC.setColor(trimColor);
offScrGC.drawOval( originX+1,
originY+1,
minDimension-2,
minDimension-2);

//绘制内框线
offScrGC.drawOval( originX + size(5),
originY + size(5),
minDimension - size(10),
minDimension - size(10));

offScrGC.setColor(textColor);

//画刻度，一共有60个刻度，x0、y0为刻度起始的位置，x1、y1圆心位置，x2、y2为刻度终止位置（x0<x2，y0<y2）
for(i=0;i<60;i++){
if(i==0 || (i>=5 && i%5 == 0)){ // x0=(int)(x1+size(40)*Math.sin(MINSEC*i));
y0=(int)(y1+size(40)*Math.cos(MINSEC*i));
}
else{ //其他部分绘制短线
x0=(int)(x1+size(42)*Math.sin(MINSEC*i));
y0=(int)(y1+size(42)*Math.cos(MINSEC*i));
}
x2=(int)(x1+size(44)*Math.sin(MINSEC*i));
y2=(int)(y1+size(44)*Math.cos(MINSEC*i));
offScrGC.drawLine(x0,y0,x2,y2);
}

drawHands(offScrGC); //绘制指针
g.drawImage(offScrImage,0,0,this); //把生成的缓冲区图形绘制到页面上

isPainted=true; //使下次UPDATE时不绘制表盘
}

public synchronized void update(Graphics g)
{
if(!isPainted)
paint(g);
else{
drawHands(offScrGC);
g.drawImage(offScrImage,0,0,this);
}
}
}

<HTML>
<TITLE></TITLE>
<BODY>
<h2></h2>
<p>
<applet code="MyClock.class" width="300" height="300">
<param name="BGCOLOR" value="FFFFFF">
<param name="FACECOLOR" value="FFFFFF">
<param name="SWEEPCOLOR" value="FF0000">
<param name="MINUTECOLOR" value="008080">
<param name="HOURCOLOR" value="000080">
<param name="TEXTCOLOR" value="000000">
<param name="CASECOLOR" value="000080">
<param name="TRIMCOLOR" value="C0C0C0">
<param name="LOGOIMAGEURL" value="java.gif">
<param name="TIMEZONE" value="8">
</p>
</BODY>
</HTML>