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在这篇文章打造通用的匀速运动框架(实例讲解)中,封装了一个匀速运动框架,我们在这个框架的基础之上,加上缓冲运动效果,然后用运动框架来做幻灯片(上下,左右)。

封装运动框架实战左右与上下滑动的焦点轮播图(实例)

缓冲运动通常有两种常见的表现:比如让一个div从0运动到500,一种是事件触发的时候,速度很快, 一种是事件触发的时候慢,然后慢慢加快.我们来实现先块后慢的,常见的就是开车,比如刚从高速路上下来的车,就是120km/小时,然后进入匝道,变成40km/时. 或者40km/小时进入小区,最后停车,变成0km/小时. 从120km/小时->40km/小时, 或者40km->0km/小时,都是速度先块后慢,这种运动怎么用程序来表示呢?

封装运动框架实战左右与上下滑动的焦点轮播图(实例)

可以用目标距离( 500 ) - 当前距离( 200 ) / 一个系数( 比如12 ),就能达到速度由块而慢的变化,当前距离在起点,分子(500 - 0 )最大,所以速度最大,如果当前距离快要接近500,分子最小,除完之后的速度也是最小。

<style>
 div{
  width: 200px;
  height: 200px;
  background:red;
  position: absolute;
  left: 0px;
 }
 </style>
 <script>
 window.onload = function(){
  var oBtn = document.querySelector( "input" ),
  oBox = document.querySelector( '#box' ),
  speed = 0, timer = null;
  oBtn.onclick = function(){
  timer = setInterval( function(){
   speed = ( 500 - oBox.offsetLeft ) / 8;
   oBox.style.left = oBox.offsetLeft + speed + 'px';
  }, 30 );
  }
 }
 </script>
</head>
<body>
 <input type="button" value="动起来">
 <div id="box"></div>
</body>
但是,div并不会乖乖地停止在500px这个目标位置,最终却是停在497.375px,只要查看当前的速度,当前的值就知道原因了 封装运动框架实战左右与上下滑动的焦点轮播图(实例)

封装运动框架实战左右与上下滑动的焦点轮播图(实例)

你会发现,速度永远都在0.375这里停着,获取到的当前的距离停在497px? 这里有个问题,我们的div不是停在497.375px吗,怎么获取到的没有了后面的小数0.375呢?计算机在处理浮点数会有精度损失。我们可以单独做一个小测试:

<div id="box"></div>
 <script>
 var oBox = document.querySelector( '#box' );
 alert( oBox.offsetLeft );
 </script>

你会发现这段代码获取到左偏移是30px而不是行间样式中写的30.2px。因为在获取当前位置的时候,会舍去小数,所以速度永远停在0.375px, 位置也是永远停在497,所以,为了到达目标,我们就得把速度变成1,对速度向上取整( Math.ceil ),我们就能把速度变成1,div也能到达500


oBtn.onclick = function(){
 timer = setInterval( function(){
 speed = ( 500 - oBox.offsetLeft ) / 8;
 if( speed > 0 ) {
  speed = Math.ceil( speed );
 }
 console.log( speed, oBox.offsetLeft );
 oBox.style.left = oBox.offsetLeft + speed + 'px';
 }, 30 );
}

第二个问题,如果div的位置是在900,也就是说从900运动到500,有没有这样的需求呢? 肯定有啊,轮播图,从右到左就是这样的啊。

<style>
 #box{
  width: 200px;
  height: 200px;
  background:red;
  position: absolute;
  left: 900px;
 }
 </style>
 <script>// <![CDATA[
 window.onload = function(){
  var oBtn = document.querySelector( "input" ),
  oBox = document.querySelector( '#box' ),
  speed = 0, timer = null;
  oBtn.onclick = function(){
  timer = setInterval( function(){
   speed = ( 500 - oBox.offsetLeft ) / 8;
   if( speed > 0 ) {
   speed = Math.ceil( speed );
   }
   oBox.style.left = oBox.offsetLeft + speed + 'px';
  }, 30 );
  }
 }
 // ]]></script>
</head>
<body>
 <input type="button" value="动起来">
 <div id="box"></div>
</body>
最后目标停在503.5px,速度这个时候是负值,最后速度停在-0.5,对于反方向的速度,我们就要把它变成-1,才能到达目标,所以用向下取整(Math.floor) 封装运动框架实战左右与上下滑动的焦点轮播图(实例)
oBtn.onclick = function(){
 timer = setInterval( function(){
 speed = ( 500 - oBox.offsetLeft ) / 8;
 if( speed > 0 ) {
  speed = Math.ceil( speed );
 }else {
  speed = Math.floor( speed );
 }
 console.log( speed, oBox.offsetLeft );
 oBox.style.left = oBox.offsetLeft + speed + 'px';
 }, 30 );
}

然后我们把这个缓冲运动整合到匀速运动框架,就变成:

function css(obj, attr, value) {
 if (arguments.length == 3) {
 obj.style[attr] = value;
 } else {
 if (obj.currentStyle) {
  return obj.currentStyle[attr];
 } else {
  return getComputedStyle(obj, false)[attr];
 }
 }
}

function animate(obj, attr, fn) {
 clearInterval(obj.timer);
 var cur = 0;
 var target = 0;
 var speed = 0;
 obj.timer = setInterval(function () {
 var bFlag = true;
 for (var key in attr) {
  if (key == 'opacity ') {
  cur = css(obj, 'opacity') * 100;
  } else {
  cur = parseInt(css(obj, key));
  }
  target = attr[key];
  speed = ( target - cur ) / 8;
  speed = speed > 0 "alpha(opacity:" + ( cur + speed ) + ")";
  } else {
   obj.style[key] = cur + speed + "px";
  }
  }
 }
 if (bFlag) {
  clearInterval(obj.timer);
  fn && fn.call(obj);
 }
 }, 30 );
}

有了这匀速运动框架,我们就来做幻灯片:

上下幻灯片的html样式文件:

<!DOCTYPE html>
<html lang="en">
<head>
 <meta charset="UTF-8">
 <title>slide - by ghostwu</title>
 <link rel="stylesheet" href="css/slide3.css" rel="external nofollow" >
 <script src="/UploadFiles/2021-04-02/animate.js">

slide3.css文件:

* {
 margin: 0;
 padding: 0;
}
li {
 list-style-type: none;
}
#slide {
 width: 800px;
 height: 450px;
 position: relative;
 margin:20px auto;
}
#slide-img {
 position: relative;
 width: 800px;
 height: 450px;
 overflow: hidden;
}
#img-container {
 position: absolute;
 left: 0px;
 top: 0px;
 height: 2250px;
 /*font-size:0px;*/
}
#img-container img {
 display: block;
 float: left;
}
#slide-nums {
 position: absolute;
 right:10px;
 bottom:10px;
}
#slide-nums li {
 float: left;
 margin:0px 10px;
 background: white;
 width: 20px;
 height: 20px;
 text-align: center;
 line-height: 20px;
 border-radius:10px;
 text-indent:-999px;
 opacity:0.6;
 filter:alpha(opacity:60);
 cursor:pointer;
}
#slide-nums li.active {
 background: red;
}

animate.js文件:

function css(obj, attr, value) {
 if (arguments.length == 3) {
 obj.style[attr] = value;
 } else {
 if (obj.currentStyle) {
  return obj.currentStyle[attr];
 } else {
  return getComputedStyle(obj, false)[attr];
 }
 }
}

function animate(obj, attr, fn) {
 clearInterval(obj.timer);
 var cur = 0;
 var target = 0;
 var speed = 0;
 obj.timer = setInterval(function () {
 var bFlag = true;
 for (var key in attr) {
  if (key == 'opacity ') {
  cur = css(obj, 'opacity') * 100;
  } else {
  cur = parseInt(css(obj, key));
  }
  target = attr[key];
  speed = ( target - cur ) / 8;
  speed = speed > 0 "alpha(opacity:" + ( cur + speed ) + ")";
  } else {
   obj.style[key] = cur + speed + "px";
  }
  }
 }
 if (bFlag) {
  clearInterval(obj.timer);
  fn && fn.call(obj);
 }
 }, 30 );
}

slide.js文件:

window.onload = function () {
 function Slide() {
 this.oImgContainer = document.getElementById("img-container");
 this.aLi = document.getElementsByTagName("li");
 this.index = 0;
 }

 Slide.prototype.bind = function () {
 var that = this;
 for (var i = 0; i < this.aLi.length; i++) {
  this.aLi[i].index = i;
  this.aLi[i].onmouseover = function () {
  that.moveTop( this.index );
  }
 }
 }

 Slide.prototype.moveTop = function (i) {
 this.index = i;
 for( var j = 0; j < this.aLi.length; j++ ){
  this.aLi[j].className = '';
 }
 this.aLi[this.index].className = 'active';
 animate( this.oImgContainer, {
  "top" : -this.index * 450,
  "left" : 0
 });
 }
 
 var oSlide = new Slide();
 oSlide.bind();

}

左右幻灯片只需要改下样式即可

样式文件:

* {
 margin: 0;
 padding: 0;
}
li {
 list-style-type: none;
}
#slide {
 width: 800px;
 height: 450px;
 position: relative;
 margin:20px auto;
}
#slide-img {
 position: relative;
 width: 800px;
 height: 450px;
 overflow: hidden;
}
#img-container {
 position: absolute;
 left: 0px;
 top: 0px;
 width: 4000px;
}
#img-container img {
 display: block;
 float: left;
}
#slide-nums {
 position: absolute;
 right:10px;
 bottom:10px;
}
#slide-nums li {
 float: left;
 margin:0px 10px;
 background: white;
 width: 20px;
 height: 20px;
 text-align: center;
 line-height: 20px;
 border-radius:10px;
 text-indent:-999px;
 opacity:0.6;
 filter:alpha(opacity:60);
 cursor:pointer;
}
#slide-nums li.active {
 background: red;
}

js调用文件:

window.onload = function () {
 function Slide() {
 this.oImgContainer = document.getElementById("img-container");
 this.aLi = document.getElementsByTagName("li");
 this.index = 0;
 }

 Slide.prototype.bind = function () {
 var that = this;
 for (var i = 0; i < this.aLi.length; i++) {
  this.aLi[i].index = i;
  this.aLi[i].onmouseover = function () {
  that.moveLeft( this.index );
  }
 }
 }

 Slide.prototype.moveLeft = function (i) {
 this.index = i;
 for( var j = 0; j < this.aLi.length; j++ ){
  this.aLi[j].className = '';
 }
 this.aLi[this.index].className = 'active';
 animate( this.oImgContainer, {
  "left" : -this.index * 800
 });
 }
 
 var oSlide = new Slide();
 oSlide.bind();

}

以上这篇封装运动框架实战左右与上下滑动的焦点轮播图(实例)就是小编分享给大家的全部内容了,希望能给大家一个参考,也希望大家多多支持。

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封装运动框架

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