Question

编写Applet程序，在屏幕上画一组同心圆，相邻两圆的直径大小相差10（pixel）(画满整个屏幕)。

用java Applet 运行:编写Applet程序，在屏幕上画一组同心圆，相邻两圆的直径大小相差10（pixel）(画满整个屏幕)。
要求：编写调用Applet程序的HTML，利用appletviewer运行HTML，启动Applet。改变Applet窗口大小，观察同心圆个数的变化情况。

Answer 1

/*
* @(#)CircleApplet.java 2010-12-29
*/
import java.awt.Graphics;

import javax.swing.*;

/**
* @author Tonk(Dongzhong)
*
*/
public class CircleApplet extends JApplet {

public void init() {
CirclePanel panel = new CirclePanel();
add(panel);
}
}

class CirclePanel extends JPanel {
public void paintComponent(Graphics g) {
super.paintComponent(g);
// 取小的长度以使圆刚好充满整个屏幕
int d = getWidth() > getHeight() ? getHeight() : getWidth();
// 得到圆心
int circleX = d / 2;
int i = 0;
// 围绕圆心画圆直到超出屏幕
while ((circleX - i * 5) > 0) {
i++;
g.drawOval(circleX - i * 5, circleX - i * 5, 2*i * 5, 2*i * 5);
}
}
}

CircleApplet.html
<applet code="CircleApplet.class" width="200" height="200">
</applet>

注意 CircleApplet.java要编译

Answer 2

import java.awt.Graphics;

import javax.swing.*;

public class MyApplet extends JApplet{

public void init(){

//g.drawArc(x, y, width, height, startAngle, arcAngle)

add(new MP());
}

class MP extends JPanel{
public void paint(Graphics g){
super.paint(g);
for(int i=0;i<2;i++)
g.drawOval(i*5, i*5, this.getHeight()-5*i, this.getHeight()-5*i);

}
}
}