JavaScript实现小球碰撞特效。类似自由落体运动。实现原理非常简单，就是动态的改变每个元素的坐标。使用radius属性将图片圆角化。使用left，top属性动态的改变小球的位置。碰撞反弹球，当碰撞到容器的边缘后，进行反弹，反向改变坐标。
首先创建Screen类，并在Screen的构造函数中给出了球移动、碰撞所需的各种属性变量，如ballsnum、spring、bounce、gravity等等 然后用原型prototype给出相应的函数，如创建球，createBalls，球碰撞hitBalls，球移动moveBalls，给每个函数添加相应的功能、
最后用按钮点击事件调用函数，仅此而已。只是我这里把点击的效果注释掉了，直接刷新页面就会随机改变。
运行效果如下：
html代码如下：html>
业余草：www.xttblog.combody {
margin:0;
padding:0;
text-align: center;
}
#screen { width: 800px; height: 640px; position: relative; background: #ccccff;margin: 0 auto;vertical-align: bottom}
#inner { position: absolute; left:0px; top:0px; width:100%; height:100%; }
#screen p {color:white;font:bold 14px;}
.one { background:url('images/QP1.png') no-repeat; background-size: 100% auto;}
.two { background:url('images/QP2.png') no-repeat; background-size: auto 100%;}
.three { background:url('images/QP3.png') no-repeat; background-size: auto 100%; }
.four { background:url('images/QP4.png') no-repeat; background-size: auto 100%;}
.five { background:url('images/QP5.png') no-repeat; background-size: auto 100%;}
.six { background:url('images/QP6.png') no-repeat; background-size: auto 100%;}
.seven { background:url('images/QP7.png') no-repeat; background-size: auto 100%; }
.eight { background:url('images/QP8.png') no-repeat; background-size: auto 100%; }
.nine { background:url('images/QP9.png') no-repeat; background-size: auto 100%;}
.ten{ background:url('images/QP10.png') no-repeat; background-size: auto 100%;}
hi test it!
相关js代码如下：var getFlag=function (id) {
return document.getElementById(id); //获取元素引用
}
var extend=function(des, src) {
for (p in src) {
des[p]=src[p];
}
return des;
}
var clss=['one','two','three','four','five','six','seven','eight','nine','ten'];
var Ball=function (diameter,classn) {
var ball=document.createElement("div");
ball.className=classn;
with(ball.style) {
width=height=diameter+'px';position='absolute';
}
return ball;
}
var Screen=function (cid,config) {
//先创建类的属性
var self=this;
if (!(self instanceof Screen)) {
return new Screen(cid,config)
}
config=extend(Screen.Config, config) //configj是extend类的实例 self.container=getFlag(cid); //窗口对象
self.container=getFlag(cid);
self.ballsnum=config.ballsnum;
self.diameter=80; //球的直径
self.radius=self.diameter/2;
self.spring=config.spring; //球相碰后的反弹力
self.bounce=config.bounce; //球碰到窗口边界后的反弹力
self.gravity=config.gravity; //球的重力
self.balls=[]; //把创建的球置于该数组变量
self.timer=null; //调用函数产生的时间id
self.L_bound=0; //container的边界
self.R_bound=self.container.clientWidth; //document.documentElement.clientWidth || document.body.clientWidth 兼容性
self.T_bound=0;
self.B_bound=self.container.clientHeight;
};
Screen.Config={ //为属性赋初值
ballsnum:10,
spring:0.8,
bounce:-0.9,
gravity:0.05
};
Screen.prototype={
initialize:function () {
var self=this;
self.createBalls();
self.timer=setInterval(function (){self.hitBalls()}, 30)
},
createBalls:function () {
var self=this,
num=self.ballsnum;
var frag=document.createDocumentFragment(); //创建文档碎片，避免多次刷新
for (i=0;i
var ball=new Ball(self.diameter,clss[i]);
//var ball=new Ball(self.diameter,clss[ Math.floor(Math.random()* num )]);//这里是随机的10个小球的碰撞效果
ball.diameter=self.diameter;
ball.radius=self.radius;
ball.style.left=(Math.random()*self.R_bound)+'px'; //球的初始位置，
ball.style.top=(Math.random()*self.B_bound)+'px';
ball.vx=Math.random() * 6 -3;
ball.vy=Math.random() * 6 -3;
frag.appendChild(ball);
self.balls[i]=ball;
}
self.container.appendChild(frag);
},
hitBalls:function () {
var self=this,
num=self.ballsnum,
balls=self.balls;
for (i=0;i
var ball1=self.balls[i];
ball1.x=ball1.offsetLeft+ball1.radius; //小球圆心坐标
ball1.y=ball1.offsetTop+ball1.radius;
for (j=i+1;j
var ball2=self.balls[j];
ball2.x=ball2.offsetLeft+ball2.radius;
ball2.y=ball2.offsetTop+ball2.radius;
dx=ball2.x-ball1.x; //两小球圆心距对应的两条直角边
dy=ball2.y-ball1.y;
var dist=Math.sqrt(dx*dx + dy*dy); //两直角边求圆心距
var misDist=ball1.radius+ball2.radius; //圆心距最小值
if(dist
//假设碰撞后球会按原方向继续做一定的运动，将其定义为运动A
var angle=Math.atan2(dy,dx);
//当刚好相碰，即dist=misDist时，tx=ballb.x, ty=ballb.y
tx=ball1.x+Math.cos(angle) * misDist;
ty=ball1.y+Math.sin(angle) * misDist;
//产生运动A后，tx > ballb.x, ty > ballb.y,所以用ax、ay记录的是运动A的值
ax=(tx-ball2.x) * self.spring;
ay=(ty-ball2.y) * self.spring;
//一个球减去ax、ay，另一个加上它，则实现反弹
ball1.vx-=ax;
ball1.vy-=ay;
ball2.vx+=ax;
ball2.vy+=ay;
}
}
}
for (i=0;i
self.moveBalls(balls[i]);
}
},
moveBalls:function (ball) {
var self=this;
ball.vy+=self.gravity;
ball.style.left=(ball.offsetLeft+ball.vx)+'px';
ball.style.top=(ball.offsetTop+ball.vy)+'px';
//判断球与窗口边界相碰，把变量名简化一下
var L=self.L_bound, R=self.R_bound, T=self.T_bound, B=self.B_bound, BC=self.bounce;
if (ball.offsetLeft
ball.style.left=L;
ball.vx*=BC;
}
else if (ball.offsetLeft + ball.diameter > R) {
ball.style.left=(R-ball.diameter)+'px';
ball.vx*=BC;
}
else if (ball.offsetTop
ball.style.top=T;
ball.vy*=BC;
}
if (ball.offsetTop + ball.diameter > B) {
ball.style.top=(B-ball.diameter)+'px';
ball.vy*=BC;
}
}
}
window.οnlοad=function() {
var sc=null;
document.getElementById("inner").innerHTML='';
sc=new Screen('inner',{ballsnum:10, spring:0.3, bounce:-0.9, gravity:0.01});
sc.initialize();
getFlag('start').οnclick=function () {
document.getElementById("inner").innerHTML='';
sc=new Screen('inner',{ballsnum:10, spring:0.3, bounce:-0.9, gravity:0.01});
sc.initialize();
}
getFlag('stop').οnclick=function() {
clearInterval(sc.timer);
}
}
看起来很简单吧！
