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

/**
* 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;
}
}
}());

View Code
　　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.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。

　　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)。

















// document.addEventListener('DOMContentLoaded',function(){
new slideIMG({
mslide: '#slideIMG',
mcontent: '#slideIMG .mcontent',
navclass: 'mhead',
auto: !!1,
delay: 5,
duration: 500
});
},false);
// ]]>
　　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：

















// document.addEventListener('DOMContentLoaded',function(){
new mSlideIMG({
mslide: '#slideIMG0',
mcontent: '#slideIMG0 .mcontent',
navclass: 'mhead',
auto: !!1,
delay: 6,
duration: 400
});

},false);
// ]]>
　　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)