Vue实现新旧版B站轮播图 | 世外天堂

Vue实现新旧版B站轮播图

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很喜欢bilibili上的轮播图造型，这次就来自己写一下B站上的轮播图吧。
首先，B站分旧版和新版，仔细观察会发现，轮播图用的明显不是一套代码，因为旧版轮播图，播到最后一张时就倒回去了，是的，因为每一张图都有过渡，必须遵循这个规则，而且不可能第一张跑在最后一张的后面，这样用户体验不是很好，但我们还是要来做一下这种轮播图。
本次采用Vue框架进行开发，当然原生js和JQuery也可以，但是Vue支持数据双向绑定，响应速度快，简单，更便于维护。

旧版轮播图

代码如下：

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<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<script src="js/vue.js" type="text/javascript" charset="utf-8"></script>
		<style type="text/css">
			* {
				margin: 0;
				padding: 0;
			}
			a{
				text-decoration: none;
			}
			li{
				list-style-type: none;
			}
			.carousel {
				max-width: 440px;
				height: 220px;
				position: relative;
				overflow: hidden;
				border-radius: 4px;
				float: left;
			}
			.carousel .pic {
				height: 220px;
				transition: 1s ease;
			}
			.carousel img {
				width: 440px;
				height: 220px;
			}
			.carousel .pic li {
				float: left;
			}
			/* 标题过渡 */
			.carousel .title li {
				position: absolute;
				bottom: 10px;
				left: 10px;
				transition: .5s;			
			}
			.carousel .title a {
				color: white;
			}
			.carousel .trig {
				position: absolute;
				right: 35px;
				bottom: 10px;
			}
			.carousel .trig li {
				float: left;
				background-image: url(img/icons.png);
				background-position: -855px -790px;
				width: 18px;
				height: 18px;
				margin-left: 5px;
				cursor: pointer;
			}
			.carousel .trig li:hover {
				background-position: -919px -790px;
			}
			.on {
				background-position: -855px -727px !important;
				width: 18px;
				height: 18px;
			}
			.show {
				opacity: 1;
			}
			.hide {
				opacity: 0;
			}
		</style>
	</head>
	<body>
		<div class="carousel" @mouseover="mouseover" @mouseout="mouseout">
			<ul class="pic" :style="style">
				<li v-for="(item,index) in pics"><a :href="pics[index].url"><img :src="pics[index].src"></a></li>
			</ul>

			<ul class="title">
				<li v-for="(item,index) in pics" :class="pics[index].on?'show':'hide'"><a :href="pics[index].url">{{pics[index].title}}</a></li>

			</ul>

			<ul class="trig">
				<li v-for="(item,index) in pics" :class="{on:pics[index].on}" @click="toggle(index)"></li>
			</ul>
		</div>
		<script>
			var vm = new Vue({
				el: '.carousel',
				data: {
					index: 0,
					time: '',
					pics: [{
							url: '#',
							src: 'img/1.jpg',
							title: '标题1',
							on: true
						},
						{
							url: '#',
							src: 'img/2.jpg',
							title: '标题2',
							on: false
						},
						{
							url: '#',
							src: 'img/3.jpg',
							title: '标题3',
							on: false
						},
						{
							url: '#',
							src: 'img/4.jpg',
							title: '标题4',
							on: false
						},
						{
							url: '#',
							src: 'img/5.jpg',
							title: '标题5',
							on: false
						}
					]
				},
				methods: {
					toggle: function(index) {
						this.index = index;
						this.pics[index].on = true;
						for (var i = 0; i < this.pics.length; i++) {
							if (i !== index)
								this.pics[i].on = false;
						}
					},
					mouseover: function() {
						clearInterval(this.time);
					},
					mouseout: function() {
						var that = this;
						this.time = setInterval(function() {
							if (that.index == that.pics.length - 1) {
								that.index = 0;
								that.pics[0].on = true;
								that.pics[that.pics.length - 1].on = false;
							} else {
								++that.index;
								that.pics[that.index].on = true;
								that.pics[that.index - 1].on = false;
							}
						}, 3000)
					}
				},
				computed: {
					style: function() {
						return {
							marginLeft: this.index * (-100) + '%',
							width: this.pics.length * 100 + '%'
						}
					},
				},
				mounted: function() {
					this.mouseout();
				}
			});
		</script>
	</body>
</html>

实现效果如图：
avatar
这种轮播图原理是一串图片通过浮动拼在一起，利用marginLeft的位移作为动画实现的，比较容易实现，缺点是中间隔几个图的时候点击感觉比较晃，而且不是无缝轮播。

新版轮播图

接下来我们就来实现一下无缝轮播图，也就是新版B站首页所用的。
代码如下：

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<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<script src="js/vue.js" type="text/javascript" charset="utf-8"></script>
		<style type="text/css">
			* {
				margin: 0;
				padding: 0;
			}

			a {
				text-decoration: none;
			}

			li {
				list-style-type: none;
			}

			.carousel {
				max-width: 440px;
				height: 220px;
				position: relative;
				overflow: hidden;
				border-radius: 4px;
				float: left;
			}

			.carousel .pic {
				width: 440px;
				height: 220px;

			}

			.carousel img {
				width: 440px;
				height: 220px;
			}

			.carousel .pic li {
				position: absolute;
				top: 0;
				left: 0;
				/* 这里一定要改成绝对定位 */
			}

			/* 标题过渡 */
			.carousel .title li {
				position: absolute;
				bottom: 10px;
				left: 10px;
				transition: .5s;
				z-index: 999999;
			}

			.carousel .title a {
				color: white;
			}

			.carousel .trig {
				position: absolute;
				right: 35px;
				bottom: 10px;
				z-index: 999999;
			}

			.carousel .trig li {
				float: left;
				background-image: url(img/icons.png);
				background-position: -855px -790px;
				width: 18px;
				height: 18px;
				margin-left: 5px;
				cursor: pointer;
			}

			.carousel .trig li:hover {
				background-position: -919px -790px;
			}

			.on {
				background-position: -855px -727px !important;
				width: 18px;
				height: 18px;
			}

			.show {
				opacity: 1;
			}

			.hide {
				opacity: 0;
			}
		</style>
	</head>
	<body>
		<div class="carousel" @mouseover="mouseover" @mouseout="mouseout">
			<ul class="pic" ref="pic">
				<li v-for="(item,index) in pics"><a :href="pics[index].url"><img :src="pics[index].src"></a></li>
			</ul>
			<ul class="title">
				<li v-for="(item,index) in pics" :class="pics[index].on?'show':'hide'"><a :href="pics[index].url">{{pics[index].title}}</a></li>
			</ul>

			<ul class="trig">
				<li v-for="(item,index) in pics" :class="{on:pics[index].on}" @click="toggle(index)"></li>
			</ul>
		</div>
		<script>
			var vm = new Vue({
				el: '.carousel',
				data: {
					index: 0,
					time: '',
					zindex: 1,
					pics: [{
							url: '#',
							src: 'img/1.jpg',
							title: '标题1',
							on: true
						},
						{
							url: '#',
							src: 'img/2.jpg',
							title: '标题2',
							on: false
						},
						{
							url: '#',
							src: 'img/3.jpg',
							title: '标题3',
							on: false
						},
						{
							url: '#',
							src: 'img/4.jpg',
							title: '标题4',
							on: false
						},
						{
							url: '#',
							src: 'img/5.jpg',
							title: '标题5',
							on: false
						}
					]
				},
				methods: {
					toggle: function(i) {
						this.index = i;
						this.pics[i].on = true;
						for (let j = 0; j < this.pics.length; j++) {
							if (j !== i)
								this.pics[j].on = false;
						}
						this.zindex++;
						this.$refs.pic.children[i].style.zIndex = this.zindex;
						this.$refs.pic.children[i].style.transform = 'translate3d(0px,0px,0px)';
						this.$refs.pic.children[i].style.transition = 'all 0.25s ease 0s';
						if (i >= 1) {
							//当前轮播图前面的全部向左移
							for (let j = 0; j < i; j++) {
								this.$refs.pic.children[j].style.transition = 'all 0.55s ease 0s';
								this.$refs.pic.children[j].style.transform = 'translate3d(-440px,0px,0px)';
							}
						} else {
							//点击第一个按钮，此时第一张图在最后一张图左边
							this.$refs.pic.children[this.pics.length - 1].style.transition = 'all 0.55s ease 0s';
							this.$refs.pic.children[this.pics.length - 1].style.transform = 'translate3d(440px,0px,0px)';
						}
						if (i < this.pics.length - 1) {
							//当前轮播图后面的全部向右移
							for (let j = i + 1; j < this.pics.length; j++) {
								this.$refs.pic.children[j].style.transition = 'all 0.55s ease 0s';
								this.$refs.pic.children[j].style.transform = 'translate3d(440px,0px,0px)';
							}
						} else {
							//点击最后一个按钮，此时第一张图在最后一张图左边
							this.$refs.pic.children[0].style.transition = 'all 0.55s ease 0s';
							this.$refs.pic.children[0].style.transform = 'translate3d(-440px,0px,0px)';
						}
					},
					mouseover: function() {
						clearInterval(this.time);
						//鼠标移入，第一张图在最后一张图左边
						if (this.index == this.pics.length - 1) {
							this.$refs.pic.children[0].style.transform = 'translate3d(-440px,0px,0px)';
						}
						//鼠标移入，第一张图在最后一张图左边
						else if(this.index ==0){
							this.$refs.pic.children[this.pics.length - 1].style.transform = 'translate3d(440px,0px,0px)';
						}
					},
					mouseout: function() {
						var that = this;
						var i = that.index;
						//鼠标移出，第一张图在最后一张图右边
						if (i == that.pics.length - 1) {
							that.$refs.pic.children[0].style.transform = 'translate3d(440px,0px,0px)';
						}
						//自动轮播
						this.time = setInterval(function() {
							that.zindex++;
							if (i == that.pics.length - 1) {
								i = 0;
							} else {
								++i
							}
							that.index = i;//必须储存index的值，否则值恒为0
							that.$refs.pic.children[i].style.zIndex = that.zindex;
							that.$refs.pic.children[i].style.transform = 'translate3d(0px,0px,0px)';
							that.$refs.pic.children[i].style.transition = 'all 0.25s ease 0s';
							that.pics[i].on = true;
							//向左移动
							if (i > 0) {
								that.$refs.pic.children[i - 1].style.transition = 'all 0.55s ease 0s';
								that.$refs.pic.children[i - 1].style.transform = 'translate3d(-440px,0px,0px)';
								that.pics[i - 1].on = false;

							} else {
								that.$refs.pic.children[that.pics.length - 1].style.transition = 'all 0.55s ease 0s';
								that.$refs.pic.children[that.pics.length - 1].style.transform = 'translate3d(-440px,0px,0px)';
								that.pics[that.pics.length - 1].on = false;
							}
							//向右移动
							if (i < that.pics.length - 1) {
								that.$refs.pic.children[i + 1].style.transition = 'none 0s ease 0s';
								that.$refs.pic.children[i + 1].style.transform = 'translate3d(440px,0px,0px)';
							} else {
								that.$refs.pic.children[0].style.transition = 'none 0s ease 0s';
								that.$refs.pic.children[0].style.transform = 'translate3d(440px,0px,0px)';
							}
						}, 3000)
					}
				},
				mounted: function() {
					this.mouseout();
					//初始状态，即0++++
					for (let j = 1; j < this.pics.length; j++) {
						this.$refs.pic.children[j].style.transform = 'translate3d(440px,0px,0px)'
					}
					this.$refs.pic.children[0].style.zIndex = '1';
				}
			});
		</script>
	</body>
</html>

这种轮播图比起上一种要复杂的多，但是看起来非常舒服，甚至比swiper的轮播图还要高档，给人的感觉就好像是两张图在相互切换，其他图在怎么变换根本看不出来。
根据我仔细的观察，分析出了原理，主要是通过translate3d变换位移，还需要加上叠放次序zindex，不然顺序会乱，你会看到其中一张图在过渡的时候压到其他图，这里的过渡要分开加，而不是写在CSS中，不是无脑加，第一张往最后一张图后面移动时不能有过渡动画，重点还要考虑第一张图和最后一张图的位置关系，这里一个过渡0.25s和一个过渡0.55s并不是没有道理,如果都设为0.55s可能会看到其它图的过渡惨杂进来
实现效果如图：
avatar