移动web：图片切换(焦点图)

　　在web页面上图片切换（焦点图）效果实在是太常见了，PC端、移动端到处都有它的身影。

　　上次写了个tab选项卡的效果，在这里延续一下，改成图片切换的效果。

　　如果不需要自动播放，稍微修改下html标签、和css样式，tab选项卡JS里动画持续时间、去掉点击切换事件部分就可以了。

　　html

<div class="mslide" id="slide">
        <ul class="mcontent">
            <li><a href="#a1"><img src="images/01.jpg" /></a></li>
            <li><a href="#a2"><img src="images/02.jpg" /></a></li>
            <li><a href="#a3"><img src="images/03.jpg" /></a></li>
            <li><a href="#a4"><img src="images/04.jpg" /></a></li>
        </ul>
        <ul class="mhead">
            <li>1</li>
            <li>2</li>
            <li>3</li>
            <li>4</li>
        </ul>
    </div><!-- End mslide -->

　　css

body,div,ul,li{margin:0;padding:0;}
ul,li{list-style: none;}
body{font-size: 100%; font-family: Helvetica,STHeiti,Droid Sans Fallback;}

.mslide {
    position:relative;
    width:100%;
    overflow:hidden;
    margin: 15px 0;
}
.mcontent {
    width:100%;
    overflow:hidden;
}
.mcontent li {
    width:100%;
    float:left;
}
.mcontent li img {
    width:100%;
}
.mhead {
    position:absolute;
    bottom:5px;
    left:0;
    z-index: 10;
    text-align:center;
    width:100%;
    height:15px;
    line-height:15px;
}
.mhead li {
    display:inline-block;
    width:10px;
    height:10px;
    border:1px solid #999;
    border-radius:6px;
    margin:0 3px;
    overflow:hidden;
    font-size:0;
    line-height:0;
    vertical-align: top;
    background: transparent;
    color:rgba(0,0,0,0);
}
.mhead li.current {
    background:#F00;
}

　　JS

/**
 * LBS mTabs  (修改成图片切换)
 * ===================================================
 * opts.mtab     tabs外围容器/滑动事件对象(一个CSS选择器)
 * opts.mhead     tabs标题容器/点击对象(一个CSS选择器)
 * opts.mcontent    tabs内容容器/滑动切换对象(一个CSS选择器) 
 * opts.index     tabs索引(默认0) 指定显示哪个索引的标题、内容
 * opts.current  tabs当前项的类名(默认current)
 * ===================================================
**/
;(function(){
window.mTabs = function(opts){
    if(typeof opts === undefined) return;

    this.mtab = document.querySelector(opts.mtab);
    this.mhead = document.querySelector(opts.mhead);
    this.mcontent = document.querySelector(opts.mcontent);

    this.mheads = this.mhead.children;
    this.mcontents = this.mcontent.children;
    
    this.length = this.mheads.length;
    if(this.length < 1) return;
    if(opts.index > this.length-1) opts.index = this.length-1;
    this.index = this.oIndex = opts.index || 0;
    this.current = opts.current || 'current';
    this.touch = {};

    this.init();
}
mTabs.prototype = {
    init: function(opts){
        this.set();
        this.initset();
        this.bind();
    },
    initset: function(){
        for(var i = 0; i < this.length; i++){
            this.mheads[i].index = i;
            this.mheads[i].className = this.mheads[i].className.replace(this.current,'');
            this.mcontents[i].className = this.mcontents[i].className.replace(this.current,'');
        } 
        this.mheads[this.index].className += ' '+this.current;
        this.mcontents[this.index].className += ' '+this.current;
        //this.mcontent.style.webkitTransform = this.mcontent.style.transform = "translateX(" + (-this.index * this.width) + "px)";
        this.mcontent.style.webkitTransform = this.mcontent.style.transform = "translate3d(" + (-this.index * this.width) + "px,0,0)";
    },
    set: function(){
        this.width =  document.documentElement.clientWidth || document.body.clientWidth;
        this.mcontent.style.width = this.length * this.width + 'px';        
        for(var i = 0; i < this.length; i++) this.mcontents[i].style.width = this.width + 'px';
        //this.mcontent.style.webkitTransform = this.mcontent.style.transform = "translateX(" + (-this.index * this.width) + "px)";
        this.mcontent.style.webkitTransform = this.mcontent.style.transform = "translate3d(" + (-this.index * this.width) + "px,0,0)";
    },
    bind: function(){
        var _this = this;
        this.mtab.addEventListener("touchstart",function(e){
            _this.touchStart(e);
        }, false);
        this.mtab.addEventListener("touchmove",function(e){
            _this.touchMove(e);
        }, false);
        this.mtab.addEventListener("touchend",function(e){
            _this.touchEnd(e);
        }, false);
        this.mtab.addEventListener("touchcancel",function(e){
            _this.touchEnd(e);
        }, false);
        this.mcontent.addEventListener('webkitTransitionEnd',function(){
            _this.transitionEnd();
        }, false);
        window.addEventListener("resize", function(){
            setTimeout(function(){
                _this.set();
            },100);
        }, false);
        window.addEventListener("orientationchange",function(){
            setTimeout(function(){
                _this.set();
            },100);
        }, false);
    },
    touchStart: function(e){
        this.touch.x = e.touches[0].pageX;
        this.touch.y = e.touches[0].pageY;
        this.touch.time = Date.now();
        this.touch.disX = 0;
        this.touch.disY = 0;
        this.touch.fixed = '';
    },
    touchMove: function(e){
        if(this.touch.fixed === 'up') return;
        e.stopPropagation();
        if(e.touches.length > 1 || e.scale && e.scale !== 1) return;
        this.touch.disX = e.touches[0].pageX - this.touch.x;
        this.touch.disY = e.touches[0].pageY - this.touch.y;
        if(this.touch.fixed === ''){
            if( Math.abs(this.touch.disY) > Math.abs(this.touch.disX) ){
                this.touch.fixed = 'up';
            }else{
                this.touch.fixed = 'left';
            }
        }
        if(this.touch.fixed === 'left'){
            e.preventDefault();
            if( (this.index === 0 && this.touch.disX > 0) || (this.index === this.length-1 && this.touch.disX < 0) ) this.touch.disX /= 4;
            //this.mcontent.style.webkitTransform = this.mcontent.style.transform = "translateX(" + ( this.touch.disX - this.index * this.width ) + "px)";
            this.mcontent.style.webkitTransform = this.mcontent.style.transform = "translate3d(" + ( this.touch.disX - this.index * this.width ) + "px,0,0)";
        } 
    },
    touchEnd: function(e){    
        if(this.touch.fixed === 'left'){
            var _this = this, X = Math.abs(this.touch.disX);
            this.mcontent.style.webkitTransition = this.mcontent.style.transition = 'all 400ms';
            if( (Date.now() - this.touch.time > 100 && X > 10) || X > this.width/2 ){
                this.touch.time = Date.now();
                this.touch.disX > 0 ? this.index-- : this.index++;
                this.index < 0 && (this.index = 0);
                this.index > this.length - 1 && (this.index = this.length - 1);
                if(this.index !== this.oIndex) this.replace();
            }
            //this.mcontent.style.webkitTransform = this.mcontent.style.transform = "translateX(" + (-this.index * this.width) + "px)";
            this.mcontent.style.webkitTransform = this.mcontent.style.transform = "translate3d(" + (-this.index * this.width) + "px,0,0)";
        }    
    },
    transitionEnd: function(){
        this.mcontent.style.webkitTransition = this.mcontent.style.transition = 'all 0ms';
    },
    replace: function(){
        this.mheads[this.index].className += ' '+this.current;
        this.mheads[this.oIndex].className = this.mheads[this.oIndex].className.replace(this.current,'').trim();
        this.mcontents[this.index].className += ' '+this.current;
        this.mcontents[this.oIndex].className = this.mcontents[this.oIndex].className.replace(this.current,'').trim();
        this.oIndex = this.index;
    }
}
}());

　　效果预览 (Chrome的移动模式、移动设备)

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• 
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• 

• 1
• 2
• 3
• 4

 　　这个根据tab选项卡修改而成的图片切换能适应大部分web页面的需求。点击下载

　　现在来加上自动播放功能，在上面的html，css基础上做出一点修改，每次手动写入导航的指示的html标签太麻烦了，让程序来判断有几张图片，然后创建几个导航指示，这样html结构更简洁。

　　html

<div class="mslide" id="slideIMG">
    <ul class="mcontent">
        <li><a href="#a1"><img src="images/01.jpg" /></a></li>
        <li><a href="#a2"><img src="images/02.jpg" /></a></li>
        <li><a href="#a3"><img src="images/03.jpg" /></a></li>
        <li><a href="#a4"><img src="images/04.jpg" /></a></li>
    </ul>
</div><!-- End mslide -->

 　　css

body,div,ul,li{margin:0;padding:0;}
ul,li{list-style: none;}
body{font-size: 100%; font-family: Helvetica,STHeiti,Droid Sans Fallback;}

.mslide {
    position:relative;
    width:100%;
    overflow:hidden;
    margin: 15px 0;
}
.mcontent {
    width:100%;
    overflow:hidden;
}
.mcontent li {
    width:100%;
    float:left;
}
.mcontent li img {
    width:100%;
}
.mhead {
    position:absolute;
    bottom:5px;
    left:0;
    z-index: 10;
    text-align:center;
    width:100%;
    height:15px;
    line-height:15px;
}
.mhead li {
    display:inline-block;
    width:10px;
    height:10px;
    border:1px solid #999;
    border-radius:6px;
    margin:0 3px;
    overflow:hidden;
    font-size:0;
    line-height:0;
    vertical-align: top;
    background: transparent;
    color:rgba(0,0,0,0);
}
.mhead li.current {
    background:#F00;
}

 　　JS代码和tab选项卡大部分相似，增加了自动播放、创建导航指示。

　　先贴JS出代码，供参考

/**
 * LBS mSlideIMG 顺序版-自动
 * Date: 2014-5-11
 * ===================================================
 * opts.mslide     外围容器/滑动事件对象(一个CSS选择器)
 * opts.mcontent  内容容器/滑动切换对象(一个CSS选择器) 
 * opts.index     索引(默认0) 指定显示哪个索引的导航指示、图片项
 * opts.navclass  导航容器的类名(默认mnav)
 * opts.current  当前项的类名(默认current)
 * opts.auto    是否自动播放 默认false
 * opts.delay    自动播放间隔时间 默认5秒 自动播放时有效
 * opts.duration    动画持续时间 默认400ms
 * ===================================================
**/
;(function(){
window.mSlideIMG = function(opts){
    if(typeof opts === undefined) return;

    this.mslide = document.querySelector(opts.mslide);
    this.mcontent = document.querySelector(opts.mcontent);
    this.mcontents = this.mcontent.children;
    this.mnav = null;
    this.mnavs = [];

    this.length = this.mcontents.length;
    if(this.length < 1) return;
    if(opts.index > this.length-1) opts.index = this.length-1;
    this.index = this.oIndex = opts.index || 0;
    
    this.current = opts.current || 'current';
    this.navclass = opts.navclass || 'mnav';

    this.duration = opts.duration || 400;
    this.auto = !!opts.auto || false;
    this.auto && (this.delay = opts.delay || 5);
    this.timer = null;
    this.touch = {};

    this.init();
}
mSlideIMG.prototype = {
    init: function(opts){
        this.set();
        this.initset();
        this.bind();
    },
    initset: function(){
        this.create();
        for(var i = 0; i < this.length; i++){ 
            if(getComputedStyle(this.mcontents[i],null).position === 'absolute') this.mcontents[i].style.position = 'relative';
            if(getComputedStyle(this.mcontents[i],null).cssFloat !== 'left') this.mcontents[i].style.cssFloat = 'left';
        } 
        this.mnavs[this.index].className = this.current;
        this.mcontents[this.index].className += ' '+this.current;
        //this.mcontent.style.webkitTransform = this.mcontent.style.transform = "translateX(" + (-this.index * this.width) + "px)";
        this.mcontent.style.webkitTransform = this.mcontent.style.transform = "translate3d(" + (-this.index * this.width) + "px,0,0)";
    },
    set: function(){
        this.width =  document.documentElement.clientWidth || document.body.clientWidth;
        this.mcontent.style.width = this.length * this.width + 'px';        
        for(var i = 0; i < this.length; i++) this.mcontents[i].style.width = this.width + 'px';
        //this.mcontent.style.webkitTransform = this.mcontent.style.transform = "translateX(" + (-this.index * this.width) + "px)";
        this.mcontent.style.webkitTransform = this.mcontent.style.transform = "translate3d(" + (-this.index * this.width) + "px,0,0)";
    },
    create: function(){
        this.mnav = document.createElement('ul'), li = null, i = 0;
        for(; i < this.length; i++){
            li = document.createElement('li');
            li.innerHTML = i+1;
            this.mnavs.push(li);
            this.mnav.appendChild(li);
        }
        this.mnav.className = this.navclass;
        this.mslide.appendChild(this.mnav);
    },
    bind: function(){
        var _this = this;
        this.mslide.addEventListener("touchstart",function(e){
            _this.touchStart(e);
            _this.auto && _this.stop();
        }, false);
        this.mslide.addEventListener("touchmove",function(e){
            _this.touchMove(e);
            _this.auto && _this.stop();
        }, false);
        this.mslide.addEventListener("touchend",function(e){
            _this.touchEnd(e);
            _this.auto && _this.start();
        }, false);
        this.mslide.addEventListener("touchcancel",function(e){
            _this.touchEnd(e);
            _this.auto && _this.start();
        }, false);
        this.mcontent.addEventListener('webkitTransitionEnd',function(){
            _this.transitionEnd();
        }, false);
        window.addEventListener("resize", function(){
            setTimeout(function(){
                _this.set();
            },100);
        }, false);
        window.addEventListener("orientationchange",function(){
            setTimeout(function(){
                _this.set();
            },100);
        }, false);
        this.auto && this.start();
    },
    touchStart: function(e){
        this.touch.x = e.touches[0].pageX;
        this.touch.y = e.touches[0].pageY;
        this.touch.time = Date.now();
        this.touch.disX = 0;
        this.touch.disY = 0;
        this.touch.fixed = '';
    },
    touchMove: function(e){
        if(this.touch.fixed === 'up') return;
        e.stopPropagation();
        if(e.touches.length > 1 || e.scale && e.scale !== 1) return;
        this.touch.disX = e.touches[0].pageX - this.touch.x;
        this.touch.disY = e.touches[0].pageY - this.touch.y;
        if(this.touch.fixed === ''){
            if( Math.abs(this.touch.disY) > Math.abs(this.touch.disX) ){
                this.touch.fixed = 'up';
            }else{
                this.touch.fixed = 'left';
            }
        }
        if(this.touch.fixed === 'left'){
            e.preventDefault();
            if( (this.index === 0 && this.touch.disX > 0) || (this.index === this.length-1 && this.touch.disX < 0) ) this.touch.disX /= 4;
            //this.mcontent.style.webkitTransform = this.mcontent.style.transform = "translateX(" + ( this.touch.disX - this.index * this.width ) + "px)";
            this.mcontent.style.webkitTransform = this.mcontent.style.transform = "translate3d(" + ( this.touch.disX - this.index * this.width ) + "px,0,0)";
        } 
    },
    touchEnd: function(e){
        if(this.touch.fixed === 'left'){
            var _this = this, X = Math.abs(this.touch.disX);
            if( (Date.now() - this.touch.time > 100 && X > 10) || X > this.width/2 ){
                this.touch.time = Date.now();
                this.touch.disX > 0 ? this.index-- : this.index++;
                this.index < 0 && (this.index = 0);
                this.index > this.length - 1 && (this.index = this.length - 1);
                if(this.index !== this.oIndex) this.replace();
            }
            this.mcontent.style.webkitTransition = this.mcontent.style.transition = 'all '+ this.duration +'ms';
            //this.mcontent.style.webkitTransform = this.mcontent.style.transform = "translateX(" + (-this.index * this.width) + "px)";
            this.mcontent.style.webkitTransform = this.mcontent.style.transform = "translate3d(" + (-this.index * this.width) + "px,0,0)";
        }
    },
    transitionEnd: function(){
        this.mcontent.style.webkitTransition = this.mcontent.style.transition = 'all 0ms';
    },
    replace: function(){
        this.mnavs[this.index].className = this.current;
        this.mnavs[this.oIndex].className = '';
        this.mcontents[this.index].className += ' '+this.current;
        this.mcontents[this.oIndex].className = this.mcontents[this.oIndex].className.replace(this.current,'').trim();
        this.oIndex = this.index;
    },
    start : function(){
        if(this.length < 2) return;
        var _this = this;
        this.timer = setInterval(function(){
            _this.index++;
             _this.index > _this.length - 1 && (_this.index = 0);
            if(_this.index !== _this.oIndex) _this.replace();
            _this.mcontent.style.webkitTransition = _this.mcontent.style.transition = 'all '+ _this.duration +'ms';
             //_this.mcontent.style.webkitTransform = _this.mcontent.style.transform = "translateX(" + (-_this.index * _this.width) + "px)";
            _this.mcontent.style.webkitTransform = _this.mcontent.style.transform = "translate3d(" + (-_this.index * _this.width) + "px,0,0)";
        },this.delay*1000);
    },
    stop : function(){
        clearInterval(this.timer);
        this.timer = null;
     } 
}
}());

　　导航指示根据有几张图片来创建 (滑动切换容器ul.mcontent -> 包裹图片li标签，这里就是判断有几个li标签)

this.mcontent = document.querySelector(opts.mcontent);
this.mcontents = this.mcontent.children;
//..
this.length = this.mcontents.length;
//..
create: function(){
	this.mnav = document.createElement('ul'), li = null, i = 0;
	for(; i < this.length; i++){
		li = document.createElement('li');
		li.innerHTML = i+1;
		this.mnavs.push(li);
		this.mnav.appendChild(li);
	}
	this.mnav.className = this.navclass;
	this.mslide.appendChild(this.mnav);
}

　　自动播放是间隔一段时间改变一个索引值来实现的，这个索引值在开始的时候默认定义为0。每间隔一段时间，这个索引值增加1。

this.index = this.oIndex = opts.index || 0;
//..
start : function(){
	//..
	this.timer = setInterval(function(){
		_this.index++;
		_this.index > _this.length - 1 && (_this.index = 0);
		//..
		_this.mcontent.style.webkitTransition = _this.mcontent.style.transition = 'all '+ _this.duration +'ms';
		_this.mcontent.style.webkitTransform = _this.mcontent.style.transform = "translate3d(" + (-_this.index * _this.width) + "px,0,0)";
	},this.delay*1000);
}

　　　有时候要清除自动播放，当用手指来切换图片时，要清除自动播放，手指离开时又开始自动播放。

stop : function(){
	clearInterval(this.timer);//清除定时
	this.timer = null;
}
//..
this.mslide.addEventListener("touchstart",function(e){
	_this.touchStart(e);
	_this.auto && _this.stop(); //手指移入 如果有自动播放则清除
}, false);
this.mslide.addEventListener("touchend",function(e){
	_this.touchEnd(e);
	_this.auto && _this.start(); //手指离开 重新开始自动播放
}, false);

　　有时同一个web页面，有好几个图片切换，希望有的能定时自动切换，有的不用定时，为程序增加一个接口设置是否自动播放，顺便把间隔时间，切换动画持续时间一起定义了。

this.auto = !!opts.auto || false; //默认没有自动播放
this.auto && (this.delay = opts.delay || 5); //默认间隔时间5秒
this.duration = opts.duration || 400; //默认动画持续时间400毫秒

　　自动播放的图片切换，差不多完成了，来看下效果 (Chrome的移动模式、移动设备)。

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• 

 　　说一些要注意的地方，外围容器(这里是类名为mslide的div标签)要设置相对或者绝对定位、并溢出隐藏；图片容器(这里是li标签)要浮动，为了都显示在一排滚动的容器(这里是类名为mcontent的ul标签)要足够宽；新建的导航指示是相对于外围容器绝对定位的，注意层级问题(这些能在样式里面定义就在样式里定义，程序为了全面可以多做判断)。

　　这个图片切换当最后一项切换到第一项时，动画跨度大，方向也和前几次相反，有时需要更自然的切换，方向都一样，每次动画距离也一样，这是一种进价的图片切换(焦点图)，也叫无缝切换。说下思路：可以采用绝对定位方式(这个例子里的li标签绝对定位，在li标签上做动画切换) ，根据索引值，在切换前修正位置，切换完成后修正位置；可以采用复制节点方式(复制这个例子里的li标签、全部或者部分)，根据索引值判断修正位置(这个例子里动画切换的对象和要修正位置对象是mcontent)。

　　可以看下效果：

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• 

 　　实际上根据业务需求，会做出不同的改变，比如图片要切换到那一项时才加载，图片切换在页面没有html标签(解析JSON数据生成标签)……不管它怎么变，只要掌握基本的原理，问题都能解决。

　　下载图片切换(焦点图)