用惯了jquery的同学,相信都很欣赏其动画引擎。确实相对比较完善!如果,如果想像力足够丰富的话,相信可以做出超出想像的效果。当然,跟2d库比起来,还是相差相当一段距离。jquery压根也不是专门为动画而设计的。模拟真实世界方面,还是不足的。但在web世界里还是游刃有余的。动画其实一直是flash的专属领地(web区哉)。只是它常常沦为黑客攻击的漏洞所在,而且要装插件,有时候文件实在太大,而且性耗实在是高啊。html5出现后,其实adobe自己都转移阵地到html5了。当然,我觉得很长一段时间内,flash是不会被放弃的。
长话短说,步入正题。仿照flash的动画原理,自己写了一个非常简单的js动画引擎。
首先,用过flash的同学都知道。flash有个时间线,上面布满了“帧”。其实每个帧都是一个镜头,镜头连贯起来就是一副动画效果。其实,这跟电影的原理也一样的,小时候玩过胶片的都知道,对着光可以看到一副副的镜头。人眼分辨两个画面的连贯是有时间限度的。如果想看不到两个画面变换时的闪烁大概30帧/秒左右,电影是24帧的。所以,如果能保证,动画切换能保证每秒30次,基本上,就做到了动画的流畅效果,但是这取决环境。所以具体情况,具体而定,其实关于这方面的知识我也是一知半解。就这个动画引擎而言,了解这么多也差不多足够了,有兴趣可以查找相关知识!
下面开始说说设计原理。
首先需要一个帧频,也就是多少帧每秒。如果有了总用时,通过开始和结束的状态差,就可以计算出整个动画下来有多少个“画面”(总帧数)。
这就需要几个参数了:初始状态\结束状态\总用时\帧频!
总帧数 = 总用时/1000*帧频
每走一帧,都计算出一个画面!
当前画面=初始状态 + (当前帧/总帧数)(结束状态-初始状态)
这就意味着,如果当前帧是最后一帧的话,当前画面===结束状态。整个过程播放完毕。
当然,上面这个例子,是以最简单的直线运动来设计的。真正用的时候,可能远比这个复杂的多,但总体的思想都一样的。
这种设计,显然有个不足的地方,不能保证时间正好是个整数帧。所以,我做的时候,向上取整,总用时可能稍长。除非1ms一帧。这是一个网友提出来的,我感觉不好就没有采用。所以这个引擎是有时间误差的。有了总帧数,当动画运行到最后一帧的时候,整个动画也就播放完。如果需要重复播放,重新把当前帧归0。这种动画有一个好处,就可以直接运行到指定帧。也就是flash里的gotoAndStop和gotoAndPlay。其实整个动画设计原理都是照着flash实现的。包括一个很重要的方法:enterFrame,每一帧计算画面就是能过它来实现的。还有其它一些方法:stop、play、next......等等因为目前来说,这个引擎是写非常简单和粗糙的,先不说这么详细了。下面先上代码和示例吧!
animate.js 动画核心
var animation = function(obj) { this.obj = obj; this.frames = 0; this.timmer = undefined; this.running = false; this.ms = []; } animation.prototype = { fps: 36, init: function(props, duration, tween) { //console.log('初始化'); this.curframe = 0; this.initstate = {}; this.props = props; this.duration = duration || 1000; this.tween = tween || function(t, b, c, d) { return t * c / d + b; }; this.frames = Math.ceil(this.duration * this.fps/1000); for (var prop in this.props) { this.initstate[prop] = { from: parseFloat($util.dom.getStyle(this.obj, prop)), to: parseFloat(this.props[prop]) }; } }, start: function() { if (!this.running && this.hasNext()) { //console.log('可以执行...'); this.ms.shift().call(this) } return this; }, //开始播放 play: function(callback) { //console.log('开始动画!'); var that = this; this.running = true; if (this.timmer) { this.stop(); } this.timmer = setInterval(function() { if (that.complete()) { that.stop(); that.running = false; if (callback) { callback.call(that); } return; } that.curframe++; that.enterFrame.call(that); }, 1000 / this.fps); return this; }, // 停止动画 stop: function() { //console.log('结束动画!'); if (this.timmer) { clearInterval(this.timmer); // 清除掉timmer id this.timmer = undefined; } }, go: function(props, duration, tween) { var that = this; //console.log(tween) this.ms.push(function() { that.init.call(that, props, duration, tween); that.play.call(that, that.start); }); return this; }, //向后一帧 next: function() { this.stop(); this.curframe++; this.curframe = this.curframe > this.frames ? this.frames: this.curframe; this.enterFrame.call(this); }, //向前一帧 prev: function() { this.stop(); this.curframe--; this.curframe = this.curframe < 0 ? 0 : this.curframe; this.enterFrame.call(this); }, //跳跃到指定帧并播放 gotoAndPlay: function(frame) { this.stop(); this.curframe = frame; this.play.call(this); }, //跳到指定帧停止播放 gotoAndStop: function(frame) { this.stop(); this.curframe = frame; this.enterFrame.call(this); }, //进入帧动作 enterFrame: function() { //console.log('进入帧:' + this.curframe) var ds; for (var prop in this.initstate) { //console.log('from: ' + this.initstate[prop]['from']) ds = this.tween(this.curframe, this.initstate[prop]['from'], this.initstate[prop]['to'] - this.initstate[prop]['from'], this.frames).toFixed(2); //console.log(prop + ':' + ds) $util.dom.setStyle(this.obj, prop, ds) } }, //动画结束 complete: function() { return this.curframe >= this.frames; }, hasNext: function() { return this.ms.length > 0; } }
下面是一个简单的工具,其中有所用到的缓动公式:
util.js
$util = { /** * 类型检测 */ type : function(obj){ var rep = /\[object\s+(\w+)\]/i; var str = Object.prototype.toString.call(obj).toLowerCase(); str.match(rep); return RegExp.$1; }, /** * 深拷贝 */ $unlink :function (object){ var unlinked; switch ($type(object)){ case 'object': unlinked = {}; for (var p in object) { unlinked[p] = $unlink(object[p]); } break; case 'array': unlinked = []; for (var i = 0, l = object.length; i < l; i++) { unlinked[i] = $unlink(object[i]); } break; default: return object; } return unlinked; }, /** *Dom 相关操作 */ dom:{ $: function(id) { return document.getElementById(id); }, getStyle: function(obj, prop) { var style = obj.currentStyle || window.getComputedStyle(obj, ''); if (obj.style.filter) { return obj.style.filter.match(/\d+/g)[0]; } return style[prop]; }, setStyle: function(obj, prop, val) { switch (prop) { case 'opacity': if($util.client.browser.ie){ obj.style.filter = 'alpha(' + prop + '=' + val*100 + ')' }else{ obj.style[prop] = val; } break; default: obj.style[prop] = val + 'px'; break; } }, setStyles: function(obj, props) { for (var prop in props) { switch (prop) { case 'opacity': if($util.client.browser.ie){ obj.style.filter = 'alpha(' + prop + '=' + props[prop] + ')' }else{ obj.style[prop] = props[prop]; } break; default: obj.style[prop] = props[prop] + 'px'; break; } } } }, /** *Event 事件相关 */ evt : { addEvent : function(oTarget, sEventType, fnHandler) { if (oTarget.addEventListener) { oTarget.addEventListener(sEventType, fnHandler, false); } else if (oTarget.attachEvent) { oTarget.attachEvent("on" + sEventType, fnHandler); } else { oTarget["on" + sEventType] = fnHandler; } }, rmEvent : function removeEventHandler (oTarget, sEventType, fnHandler) { if (oTarget.removeEventListener) { oTarget.removeEventListener(sEventType, fnHandler, false); } else if (oTarget.detachEvent) { oTarget.detachEvent("on" + sEventType, fnHandler); } else { oTarget["on" + sEventType] = null; } } }, /** *Ajax 异步加载 */ ajax : { request:function (options) { var xhr, res; var url = options.url, context = options.context, success = options.success, type = options.type, datatype = options.datatype, async = options.async, send = options.send, headers = options.headers; try { xhr = new XMLHttpRequest(); } catch(e) { try { xhr = new ActiveXObject('MSXML2.XMLHTTP'); } catch(e) { xhr = new ActiveXObject('Microsoft.XMLHTTP'); } } xhr.onreadystatechange = function() { if (xhr.readyState == 4 && xhr.status == 200) { res = xhr.responseText; success(res); } } xhr.open(type, url, async); xhr.send(send); } }, /** *Array 数组相关 */ array : { minIndex : function(ary){ return Math.min.apply(null,ary); }, maxitem : function(ary){ return Math.max.apply(null,ary); } }, /** *Client 客户端检测 */ client : function(){ // 浏览器渲染引擎 engines var engine = { ie: 0, gecko: 0, webkit: 0, khtml: 0, opera: 0, //complete version ver: null }; // 浏览器 var browser = { //browsers ie: 0, firefox: 0, safari: 0, konq: 0, opera: 0, chrome: 0, //specific version ver: null }; // 客户端平台platform/device/OS var system = { win: false, mac: false, x11: false, //移动设备 iphone: false, ipod: false, ipad: false, ios: false, android: false, nokiaN: false, winMobile: false, //game systems wii: false, ps: false }; // 检测浏览器引擎 var ua = navigator.userAgent; if (window.opera){ engine.ver = browser.ver = window.opera.version(); engine.opera = browser.opera = parseFloat(engine.ver); } else if (/AppleWebKit\/(\S+)/.test(ua)){ engine.ver = RegExp["$1"]; engine.webkit = parseFloat(engine.ver); //figure out if it's Chrome or Safari if (/Chrome\/(\S+)/.test(ua)){ browser.ver = RegExp["$1"]; browser.chrome = parseFloat(browser.ver); } else if (/Version\/(\S+)/.test(ua)){ browser.ver = RegExp["$1"]; browser.safari = parseFloat(browser.ver); } else { //approximate version var safariVersion = 1; if (engine.webkit < 100){ safariVersion = 1; } else if (engine.webkit < 312){ safariVersion = 1.2; } else if (engine.webkit < 412){ safariVersion = 1.3; } else { safariVersion = 2; } browser.safari = browser.ver = safariVersion; } } else if (/KHTML\/(\S+)/.test(ua) || /Konqueror\/([^;]+)/.test(ua)){ engine.ver = browser.ver = RegExp["$1"]; engine.khtml = browser.konq = parseFloat(engine.ver); } else if (/rv:([^\)]+)\) Gecko\/\d{8}/.test(ua)){ engine.ver = RegExp["$1"]; engine.gecko = parseFloat(engine.ver); //determine if it's Firefox if (/Firefox\/(\S+)/.test(ua)){ browser.ver = RegExp["$1"]; browser.firefox = parseFloat(browser.ver); } } else if (/MSIE ([^;]+)/.test(ua)){ engine.ver = browser.ver = RegExp["$1"]; engine.ie = browser.ie = parseFloat(engine.ver); } //detect browsers browser.ie = engine.ie; browser.opera = engine.opera; //detect platform var p = navigator.platform; system.win = p.indexOf("Win") == 0; system.mac = p.indexOf("Mac") == 0; system.x11 = (p == "X11") || (p.indexOf("Linux") == 0); //detect windows operating systems if (system.win){ if (/Win(?:dows )?([^do]{2})\s?(\d+\.\d+)?/.test(ua)){ if (RegExp["$1"] == "NT"){ switch(RegExp["$2"]){ case "5.0": system.win = "2000"; break; case "5.1": system.win = "XP"; break; case "6.0": system.win = "Vista"; break; case "6.1": system.win = "7"; break; default: system.win = "NT"; break; } } else if (RegExp["$1"] == "9x"){ system.win = "ME"; } else { system.win = RegExp["$1"]; } } } //mobile devices system.iphone = ua.indexOf("iPhone") > -1; system.ipod = ua.indexOf("iPod") > -1; system.ipad = ua.indexOf("iPad") > -1; system.nokiaN = ua.indexOf("NokiaN") > -1; //windows mobile if (system.win == "CE"){ system.winMobile = system.win; } else if (system.win == "Ph"){ if(/Windows Phone OS (\d+.\d+)/.test(ua)){; system.win = "Phone"; system.winMobile = parseFloat(RegExp["$1"]); } } //determine iOS version if (system.mac && ua.indexOf("Mobile") > -1){ if (/CPU (?:iPhone )?OS (\d+_\d+)/.test(ua)){ system.ios = parseFloat(RegExp.$1.replace("_", ".")); } else { system.ios = 2; //can't really detect - so guess } } //determine Android version if (/Android (\d+\.\d+)/.test(ua)){ system.android = parseFloat(RegExp.$1); } //gaming systems system.wii = ua.indexOf("Wii") > -1; system.ps = /playstation/i.test(ua); //return it return { engine: engine, browser: browser, system: system }; }(), /** *Tween 缓动相关 */ 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; } } } }
下面是个应用:
DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<title>无标题文档title>
<script src="util.js" type="text/javascript">script>
<script src="animate.js" type="text/javascript">script>
<style type="text/css">
body{behavior:url("csshover.htc")}
*{padding:0;margin:0}
.mianbox{width:480px;margin:50px auto;height:240px;}
.leftbtn{width:20px;background:#eee;border:1px solid #ddd;float:left;margin-right:8px;height:240px;}
.leftbtn:hover{background:#fff}
.rightbtn{width:20px;background:#eee;border:1px solid #ddd;float:right;height:240px;}
.rightbtn:hover{background:#fff}
.con{width:420px;float:left;height:240px;overflow:hidden;position:relative}
.con ul{ white-space:nowrap;font-size:0;position:absolute;left:0;top:0;}
.con li{display:inline; vertical-align:bottom;margin-right:10px}
style>
head>
<body>
<div class="mianbox">
<div class="leftbtn" id="leftbtn">div>
<div class="con">
<ul>
<li><img src="http://pic25.nipic.com/20121121/2969675_091845785000_2.jpg" width="205" height="240" />li>
<li><img src="http://pic23.nipic.com/20120818/9715349_114354586392_2.jpg" width="205" height="240" />li>
<li><img src="http://pic20.nipic.com/20120329/9715349_154806479182_2.jpg" width="205" height="240" />li>
<li><img src="http://pic20.nipic.com/20120329/9715349_162301568121_2.jpg" width="205" height="240" />li>
<li><img src="http://pic23.nipic.com/20120824/9715349_160522342186_2.jpg" width="205" height="240" />li>
<li><img src="http://pic23.nipic.com/20120824/9715349_160651385195_2.jpg" width="205" height="240" />li>
<li><img src="http://pic20.nipic.com/20120329/9715349_163520278182_2.jpg" width="205" height="240" />li>
<li><img src="http://pic23.nipic.com/20120827/9715349_110350505124_2.jpg" width="205" height="240" />li>
ul>
div>
<div class="rightbtn" id="rightbtn">div>
div>
<script>
/**
* @para obj 内容对象
* @para lbtn 左按钮
* @para rbtn 右按钮
* @para w 每次滚动的宽
* @para duration 每次运行时间
* @para tween 缓动类型
*/
function scOnce(obj, lbtn, rbtn, w, autotime, duration,tween){
var am = new animation(_ul),
step=0,
ulen = obj.scrollWidth,
timmerm
dr = 'left',
that = this;
// 最右端?
function isr(){
return parseInt($util.dom.getStyle(obj, 'left')) >=0;
}
// 最左端?
function isl(){
return ulen - Math.abs(parseInt($util.dom.getStyle(obj, 'left')))-10 <= w;
}
if(isr()&&isl())
return;
// 左移
this.goleft = function (){
step += -1*w;
am.go({left:step+"px"},duration,tween).start();
}
// 右移
this.goright = function (){
step += w;
am.go({left:step+"px"},duration,tween).start();
}
// 注册左按钮事件
$util.evt.addEvent(lbtn,'click',function(){
isl()? that.goright():that.goleft();
})
// 注册右按钮事件
$util.evt.addEvent(rbtn,'click',function(){
isr()? that.goleft():that.goright();
})
$util.evt.addEvent(rbtn,'mouseover',function(){
clearTimeout(timmer);
})
$util.evt.addEvent(lbtn,'mouseover',function(){
clearTimeout(timmer);
})
$util.evt.addEvent(rbtn,'mouseout',function(){
timmer = setInterval(auto,autotime);
})
$util.evt.addEvent(lbtn,'mouseout',function(){
timmer = setInterval(auto,autotime);
})
function auto(){
if(isl()){
dr = "right";
}
if(isr()){
dr = "left";
}
that['go'+dr]();
}
timmer = setInterval(auto,autotime);
}
var _ul = document.getElementsByTagName('ul')[0],
lbtn = document.getElementById('leftbtn'),
rbtn = document.getElementById('rightbtn');
var startgo = new scOnce(_ul,lbtn,rbtn,430,3000,500,$util.tween.Quint.easeInOut);
script>
body>
html>