## JS Tween动画效果研究 : - )Tween公式使用

2013-01-16 17:20  VVG  阅读(13091)  评论(2编辑  收藏

DEMO:点击直接查看

Tween中的方法接受4个参数t,b,c,d 。返回值为计算后的当前位置.

t => time(初始记步次数)   b => begin(初始位置)   c => change(变化量)   d => duration(持续次数)

Quad:{
easeIn:function (t, b, c, d) {
return c * (t /= d) * t + b;
},
easeOut:function (t, b, c, d) {
return -c * (t /= d) * (t - 2) + b;
},
easeInOut:function (t, b, c, d) {
if ((t /= d / 2) < 1) return c / 2 * t * t + b;
return -c / 2 * ((--t) * (t - 2) - 1) + b;
}
}

function MoveTo(options) { //参数o,t,b,c,d  ***** o为移动对象   t => time(初始记步次数)  b => begin(初始位置)   c => change(变化量)   d => duration(持续次数)
var o = options.o, // 移动对象
t = options.t || 0, // 初始步进
lb = options.lb || 0, // 初始left距离
tb = options.tb || 0, // 初始top距离
lc = options.lc || 500, // left变化的距离
tc = options.tc || 0, // top变化的距离
d = options.d || 500, // 变化次数，次数越多速度越慢
tween = options.tween || Tween.Elastic.easeOut;        // 移动方式，套用公式

(function () {
if (o) {
if (lc > 0){
o.style.left = Math.ceil(tween(t, lb, lc, d)) + "px";

}
if (tc > 0) {
o.style.top = Math.ceil(tween(t, tb, tc, d)) + "px";
}
if (t < d) {
t++;
setTimeout(arguments.callee, 10);
}
}
})()
}

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Tween动画效果</title>
<style type="text/css">
#vvg { text-align: center; font-size: 16px; font-weight: bold; }
#box { width: 520px; height: 50px; border: 1px solid #333; margin: 10px auto; position: relative; }
#sbox { width: 20px; height: 50px; position: absolute; left: 0; background: red; }
#graph{ border: 1px solid #ccc; background: #272424;}
#vvg .radios{width: 520px; margin: 5px auto; font-weight: normal; text-align: left; overflow: hidden;}
#vvg .radios label{ width:103px; float: left;}
#vvg .row1{ background: #cccccc;}
#vvg .row2{ background: #b6b6b6; margin-top: 10px;}
#vvg .btn{padding: 5px 40px;}
</style>
</head>
<body>
<div id="vvg">
<div id="box">
<div id="sbox">&nbsp;</div>
</div>
<canvas id="graph" width="522px" height="500">你的浏览器不支持canvas</canvas>
<div class="radios row1" id="radio_1">
<label><input type="radio" value="Linear" name="tname" checked>Linear</label>
<label><input type="radio" value="Quad" name="tname">Quad </label>
<label><input type="radio" value="Cubic" name="tname">Cubic </label>
<label><input type="radio" value="Quart" name="tname">Quart </label>
<label><input type="radio" value="Quint" name="tname">Quint</label>
<label><input type="radio" value="Sine" name="tname">Sine</label>
<label><input type="radio" value="Expo" name="tname">Expo</label>
<label><input type="radio" value="Circ" name="tname">Circ</label>
<label><input type="radio" value="Elastic" name="tname">Elastic</label>
<label><input type="radio" value="Back" name="tname">Back</label>
<label><input type="radio" value="Bounce" name="tname">Bounce</label>
</div>
<div class="radios row2" id="radio_2">
<label><input type="radio" value="easeIn" name="tname2"  checked>easeIn</label>
<label><input type="radio" value="easeOut" name="tname2">easeOut</label>
<label><input type="radio" value="easeInOut" name="tname2">easeInOut</label>
</div>
<div><input type="button" value="运 行" class="btn" id="run"></div>
</div>

<script type="text/javascript">
// 快捷选择函数
function $(arg, context) { var tagAll, n, eles = [], i, sub = arg.substring(1); context = context || document; if (typeof arg == 'string') { switch (arg.charAt(0)) { case '#': return document.getElementById(sub); break; case '.': if (context.getElementsByClassName) return context.getElementsByClassName(sub); tagAll =$('*', context);
n = tagAll.length;
for (i = 0; i < n; i++) {
if (tagAll[i].className.indexOf(sub) > -1) eles.push(tagAll[i]);
}
return eles;
break;
default:
return context.getElementsByTagName(arg);
break;
}
}
}

var Tween = {
Linear:function (t, b, c, d) {
return c * t / d + b;
},
Quad:{
easeIn:function (t, b, c, d) {
return c * (t /= d) * t + b;
},
easeOut:function (t, b, c, d) {
return -c * (t /= d) * (t - 2) + b;
},
easeInOut:function (t, b, c, d) {
if ((t /= d / 2) < 1) return c / 2 * t * t + b;
return -c / 2 * ((--t) * (t - 2) - 1) + b;
}
},
Cubic:{
easeIn:function (t, b, c, d) {
return c * (t /= d) * t * t + b;
},
easeOut:function (t, b, c, d) {
return c * ((t = t / d - 1) * t * t + 1) + b;
},
easeInOut:function (t, b, c, d) {
if ((t /= d / 2) < 1) return c / 2 * t * t * t + b;
return c / 2 * ((t -= 2) * t * t + 2) + b;
}
},
Quart:{
easeIn:function (t, b, c, d) {
return c * (t /= d) * t * t * t + b;
},
easeOut:function (t, b, c, d) {
return -c * ((t = t / d - 1) * t * t * t - 1) + b;
},
easeInOut:function (t, b, c, d) {
if ((t /= d / 2) < 1) return c / 2 * t * t * t * t + b;
return -c / 2 * ((t -= 2) * t * t * t - 2) + b;
}
},
Quint:{
easeIn:function (t, b, c, d) {
return c * (t /= d) * t * t * t * t + b;
},
easeOut:function (t, b, c, d) {
return c * ((t = t / d - 1) * t * t * t * t + 1) + b;
},
easeInOut:function (t, b, c, d) {
if ((t /= d / 2) < 1) return c / 2 * t * t * t * t * t + b;
return c / 2 * ((t -= 2) * t * t * t * t + 2) + b;
}
},
Sine:{
easeIn:function (t, b, c, d) {
return -c * Math.cos(t / d * (Math.PI / 2)) + c + b;
},
easeOut:function (t, b, c, d) {
return c * Math.sin(t / d * (Math.PI / 2)) + b;
},
easeInOut:function (t, b, c, d) {
return -c / 2 * (Math.cos(Math.PI * t / d) - 1) + b;
}
},
Expo:{
easeIn:function (t, b, c, d) {
return (t == 0) ? b : c * Math.pow(2, 10 * (t / d - 1)) + b;
},
easeOut:function (t, b, c, d) {
return (t == d) ? b + c : c * (-Math.pow(2, -10 * t / d) + 1) + b;
},
easeInOut:function (t, b, c, d) {
if (t == 0) return b;
if (t == d) return b + c;
if ((t /= d / 2) < 1) return c / 2 * Math.pow(2, 10 * (t - 1)) + b;
return c / 2 * (-Math.pow(2, -10 * --t) + 2) + b;
}
},
Circ:{
easeIn:function (t, b, c, d) {
return -c * (Math.sqrt(1 - (t /= d) * t) - 1) + b;
},
easeOut:function (t, b, c, d) {
return c * Math.sqrt(1 - (t = t / d - 1) * t) + b;
},
easeInOut:function (t, b, c, d) {
if ((t /= d / 2) < 1) return -c / 2 * (Math.sqrt(1 - t * t) - 1) + b;
return c / 2 * (Math.sqrt(1 - (t -= 2) * t) + 1) + b;
}
},
Elastic:{
easeIn:function (t, b, c, d, a, p) {
if (t == 0) return b;
if ((t /= d) == 1) return b + c;
if (!p) p = d * .3;
if (!a || a < Math.abs(c)) {
a = c;
var s = p / 4;
}
else var s = p / (2 * Math.PI) * Math.asin(c / a);
return -(a * Math.pow(2, 10 * (t -= 1)) * Math.sin((t * d - s) * (2 * Math.PI) / p)) + b;
},
easeOut:function (t, b, c, d, a, p) {
if (t == 0) return b;
if ((t /= d) == 1) return b + c;
if (!p) p = d * .3;
if (!a || a < Math.abs(c)) {
a = c;
var s = p / 4;
}
else var s = p / (2 * Math.PI) * Math.asin(c / a);
return (a * Math.pow(2, -10 * t) * Math.sin((t * d - s) * (2 * Math.PI) / p) + c + b);
},
easeInOut:function (t, b, c, d, a, p) {
if (t == 0) return b;
if ((t /= d / 2) == 2) return b + c;
if (!p) p = d * (.3 * 1.5);
if (!a || a < Math.abs(c)) {
a = c;
var s = p / 4;
}
else var s = p / (2 * Math.PI) * Math.asin(c / a);
if (t < 1) return -.5 * (a * Math.pow(2, 10 * (t -= 1)) * Math.sin((t * d - s) * (2 * Math.PI) / p)) + b;
return a * Math.pow(2, -10 * (t -= 1)) * Math.sin((t * d - s) * (2 * Math.PI) / p) * .5 + c + b;
}
},
Back:{
easeIn:function (t, b, c, d, s) {
if (s == undefined) s = 1.70158;
return c * (t /= d) * t * ((s + 1) * t - s) + b;
},
easeOut:function (t, b, c, d, s) {
if (s == undefined) s = 1.70158;
return c * ((t = t / d - 1) * t * ((s + 1) * t + s) + 1) + b;
},
easeInOut:function (t, b, c, d, s) {
if (s == undefined) s = 1.70158;
if ((t /= d / 2) < 1) return c / 2 * (t * t * (((s *= (1.525)) + 1) * t - s)) + b;
return c / 2 * ((t -= 2) * t * (((s *= (1.525)) + 1) * t + s) + 2) + b;
}
},
Bounce:{
easeIn:function (t, b, c, d) {
return c - Tween.Bounce.easeOut(d - t, 0, c, d) + b;
},
easeOut:function (t, b, c, d) {
if ((t /= d) < (1 / 2.75)) {
return c * (7.5625 * t * t) + b;
} else if (t < (2 / 2.75)) {
return c * (7.5625 * (t -= (1.5 / 2.75)) * t + .75) + b;
} else if (t < (2.5 / 2.75)) {
return c * (7.5625 * (t -= (2.25 / 2.75)) * t + .9375) + b;
} else {
return c * (7.5625 * (t -= (2.625 / 2.75)) * t + .984375) + b;
}
},
easeInOut:function (t, b, c, d) {
if (t < d / 2) return Tween.Bounce.easeIn(t * 2, 0, c, d) * .5 + b;
else return Tween.Bounce.easeOut(t * 2 - d, 0, c, d) * .5 + c * .5 + b;
}
}
}
//Tween中的方法接受4个参数t,b,c,d 。t为初始时间 b、c、d三个参数（即初始值，变化量，持续时间）。返回值为当前位置
//t => time(初始记步次数)  b => begin(初始位置)   c => change(变化量)   d => duration(持续次数)
/*
先通过上面的坐标实例说一下算法原理：

x轴是时间，y轴是当前值，b是y轴的初始值，x轴的初始值是0，t是当前时间。当t（x轴）逐渐增加到达d时，当前值（y轴）会到达目标值（b+c）。
想详细理解的话可以找资料看看吧（貌似跟数学关系比较大）。

下面就介绍如何使用这个Tween了，首先b、c、d三个参数（即初始值，变化量，持续时间）在缓动开始前，是需要先确定好的。
举一个简单的例子，一个div要向右缓动，left初始值是50，那么b就是50，要向右移动100，那c就是100，如果知道的是目标值，例如要向右移动到150，那就把目标值150减初始值b就是变化量c了。
至于d的设置就比较灵活，只要符合t是从0向d递增（或递减）就可以了。

d跟步长配合使用来设置持续时间，例如d设置为100，如果设置步长是1，那么从0到100就有100步，即分100次来完成这个过程，步数越多那么持续时间就越长。
至于t的变化相当于时间的变化，一般是均匀变化的，每次变化都增加一个步长，当t从0递增（或递减）到d时，缓动就结束了。

要注意的是t是从0开始的，设置步长时必须确定t确实能到达d，如果上面的步长是3，那么t就永远都到不了d了。更好的处理是当t等于或超过d之后，就停止定时器并设置当前值为目标值。
*/

// 获取radio值
var radio_1 = function(){
var radios = $('input',$('#radio_1'));
for(var i = 0,n=radios.length;i<n;i++){
if(radios[i].checked == true){
return radios[i].value;
}
}
};

var radio_2 = function(){
var radios = $('input',$('#radio_2'));
for(var i = 0,n=radios.length;i<n;i++){
if(radios[i].checked == true){
return radios[i].value;
}
}
};

// 移动动画
function MoveTo(options) { //参数o,t,b,c,d  ***** o为移动对象   t => time(初始记步次数)  b => begin(初始位置)   c => change(变化量)   d => duration(持续次数)
var o = options.o, // 移动对象
t = options.t || 0, // 初始步进
lb = options.lb || 0, // 初始left距离
tb = options.tb || 0, // 初始top距离
lc = options.lc || 500, // left变化的距离
tc = options.tc || 0, // top变化的距离
d = options.d || 500, // 变化次数，次数越多速度越慢
tween = options.tween || Tween.Elastic.easeOut;        // 移动方式，套用公式
// 绘图处=============================不用绘图可去掉
var canvas = document.getElementById('graph');
var context = canvas.getContext('2d');
context.clearRect(0,0,500,500);
// ================================== end

(function () {
if (o) {
if (lc > 0){
o.style.left = Math.ceil(tween(t, lb, lc, d)) + "px";
// 绘图区域开始，可以去掉 ==============================
drawPoint({
canvas:canvas,
left:Math.ceil(t*5),
top: Math.ceil(tween(t, lb, lc, d))
})
// 绘图区域结束 ======================================
}
if (tc > 0) {
o.style.top = Math.ceil(tween(t, tb, tc, d)) + "px";
}
if (t < d) {
t++;
setTimeout(arguments.callee, 10);
}
}
})()
}
// 绘制曲线图
function drawPoint(options){
var canvas = options.canvas;    //画布
var left = options.left;        // time
var top = options.top;    // 当前值
var context = canvas.getContext('2d');
// 绘制点
context.fillStyle = '#fff';
context.fillRect(left,top,2,2);
}

\$("#run").onclick = function(){
var div = document.getElementById('sbox');
var tween1 = radio_1();
var tween2 = radio_2();
if(!!Tween[tween1][tween2]){
var tween = Tween[tween1][tween2];
}else{
tween =  Tween[tween1];
}
var options = {
o:div,
lc:500,
d:100,
tween:tween
}
MoveTo(options);
}

</script>
</body>
</html>