Question

java程序:编写一个程序,让一个小球在JFrame中滚动,当碰边缘时则选择一个角度返回.

Answer 1

05年写的，你修改一下吧

/*
* 一个在窗体中来回运动的圆.java
*
* Created on 2005年10月5日, 下午1:02
*
* To change this template, choose Tools | Options and locate the template under
* the Source Creation and Management node. Right-click the template and choose
* Open. You can then make changes to the template in the Source Editor.
*/

package javaapplication1;

import java.applet.Applet;
import java.awt.Color;
import java.awt.Event;
import java.awt.Graphics;
import java.applet.*;
import java.awt.*;
import java.math.*;
/**
*
* @author Bachelorlrz
*/
public class 在窗体中来回运动的圆 extends java.applet.Applet implements java.lang.Runnable {
int cx,cy,c1x,c1y; //圆的坐标
int cw,ch; //圆的宽高
int bx,by,bw,bh; //背景的坐标和宽高
int dx,dx1; //圆的运动
int r,rx,ry; //圆的半径和位置
int r1,r1x,r1y;
Thread u_thread;

/** Initialization method that will be called after the applet is loaded
* into the browser.
*/
public void init() {
rx=150; ry=160;
bw=500; bh=400;
r1x=bw/2-cw*2; r1y=bh/2-ch;
r=60; r1=200;
cx =rx; cy =ry;
c1x=r1x; c1y=r1y;
cw=30; ch=30;
bx=2; by=2;
dx=1; dx1=2;
// TODO start asynchronous download of heavy resources
}

// TODO overwrite start(), stop() and destroy() methods

public void update(java.awt.Graphics g) {

super.paint(g);
g.setColor(Color.red);
g.drawRect(bx,by,bw,bh);
g.setColor(Color.BLACK);
g.fillRect(bx+2,by+2,bw-4,bh-4);
g.drawString("在窗体中来回运动的圆", bw/2-60, bh/2);
if (cx<rx-r || cx>rx+r) {
dx = -dx;
}
if (c1x<r1x-r1 || c1x>r1x+r1) {
dx1 = -dx1;
}

cx =cx+dx;
cy =(int)(dx*Math.sqrt(r*r-(cx-rx)*(cx-rx)))+ry;
c1x =c1x+dx1;
c1y =(int)(dx1/2*Math.sqrt(r1*r1-(c1x-r1x)*(c1x-r1x))/2);

// g.drawArc(cx, cy, cw, ch, 0, 360);

for(int i=0;i<8;i++){
if (i%5 == 0){
g.setColor(Color.black);
}else if ( i%5== 1) {
g.setColor(Color.GREEN);
}else if(i%5==2){
g.setColor(Color.RED);
}else if( i%5 ==3){
g.setColor(Color.pink);
}else {
g.setColor(Color.orange);
}
g.drawLine(bx,by, cx+10,cy+i+10);
g.drawLine(bx+bw,by+bh,cx+10,cy+i+10);
g.drawLine(bx+bw,by, cx+10,cy+i+10);
g.drawLine(bx,by+bh, cx+10,cy+i+10);

g.drawLine(bx,by,-cx+bw-bx-cw+10,cy+i+10);
g.drawLine(bx+bw,by+bh,-cx+bw-bx-cw+10,cy+i+10);
g.drawLine(bx+bw,by,-cx+bw-bx-cw+10,cy+i+10);
g.drawLine(bx,by+bh,-cx+bw-bx-cw+10,cy+i+10);

g.drawLine(bx,by, c1x+10,c1y+r1y+i+10);
g.drawLine(bx+bw,by+bh,c1x+10,c1y+r1y+i+10);
g.drawLine(bx+bw,by, c1x+10,c1y+r1y+i+10);
g.drawLine(bx,by+bh, c1x+10,c1y+r1y+i+10);

g.drawLine(bx,by, r1x+r1+cw-c1x+10,-c1y+r1y+i+10);
g.drawLine(bx+bw,by+bh,r1x+r1+cw-c1x+10,-c1y+r1y+i+10);
g.drawLine(bx+bw,by, r1x+r1+cw-c1x+10,-c1y+r1y+i+10);
g.drawLine(bx,by+bh,r1x+r1+cw-c1x+10,-c1y+r1y+i+10);

g.drawArc(cx+i, cy+i, cw-i*2, ch-i*2, 0, 360);
g.drawArc(-cx+bw-bx-cw+i, cy+i, cw-i*2, ch-i*2, 0, 360);
g.drawArc(c1x+i, c1y+r1y+i, cw-i*2, ch-i*2, 0, 360);
g.drawArc(r1x+r1+cw-c1x+i, -c1y+r1y+i, cw-i*2, ch-i*2, 0, 360);
}
}
public void start(){
if (u_thread == null)
{
u_thread = new Thread(this);
u_thread.start();
}
}
public void run() {
while(true){
repaint();
try{
u_thread.sleep(10);
}
catch (InterruptedException e){
return;
}
}
}
}