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3 years ago
/**
@Name flow 流加载组件
@LicenseMIT
*/
layui.define('jquery', function(exports){
"use strict";
var $ = layui.$, Flow = function(options){}
,ELEM_MORE = 'layui-flow-more'
,ELEM_LOAD = '<i class="layui-anim layui-anim-rotate layui-anim-loop layui-icon ">&#xe63e;</i>';
//主方法
Flow.prototype.load = function(options){
var that = this, page = 0, lock, isOver, lazyimg, timer;
options = options || {};
var elem = $(options.elem); if(!elem[0]) return;
var scrollElem = $(options.scrollElem || document); //滚动条所在元素
var mb = options.mb || 50; //与底部的临界距离
var isAuto = 'isAuto' in options ? options.isAuto : true; //是否自动滚动加载
var end = options.end || '没有更多了'; //“末页”显示文案
//滚动条所在元素是否为document
var notDocment = options.scrollElem && options.scrollElem !== document;
//加载更多
var ELEM_TEXT = '<cite>加载更多</cite>'
,more = $('<div class="layui-flow-more"><a href="javascript:;">'+ ELEM_TEXT +'</a></div>');
if(!elem.find('.layui-flow-more')[0]){
elem.append(more);
}
//加载下一个元素
var next = function(html, over){
html = $(html);
more.before(html);
over = over == 0 ? true : null;
over ? more.html(end) : more.find('a').html(ELEM_TEXT);
isOver = over;
lock = null;
lazyimg && lazyimg();
};
//触发请求
var done = function(){
lock = true;
more.find('a').html(ELEM_LOAD);
typeof options.done === 'function' && options.done(++page, next);
};
done();
//不自动滚动加载
more.find('a').on('click', function(){
var othis = $(this);
if(isOver) return;
lock || done();
});
//如果允许图片懒加载
if(options.isLazyimg){
var lazyimg = that.lazyimg({
elem: options.elem + ' img'
,scrollElem: options.scrollElem
});
}
if(!isAuto) return that;
scrollElem.on('scroll', function(){
var othis = $(this), top = othis.scrollTop();
if(timer) clearTimeout(timer);
if(isOver || !elem.width()) return; //如果已经结束,或者元素处于隐藏状态,则不执行滚动加载
timer = setTimeout(function(){
//计算滚动所在容器的可视高度
var height = notDocment ? othis.height() : $(window).height();
//计算滚动所在容器的实际高度
var scrollHeight = notDocment
? othis.prop('scrollHeight')
: document.documentElement.scrollHeight;
//临界点
if(scrollHeight - top - height <= mb){
lock || done();
}
}, 100);
});
return that;
};
//图片懒加载
Flow.prototype.lazyimg = function(options){
var that = this, index = 0, haveScroll;
options = options || {};
var scrollElem = $(options.scrollElem || document); //滚动条所在元素
var elem = options.elem || 'img';
//滚动条所在元素是否为document
var notDocment = options.scrollElem && options.scrollElem !== document;
//显示图片
var show = function(item, height){
var start = scrollElem.scrollTop(), end = start + height;
var elemTop = notDocment ? function(){
return item.offset().top - scrollElem.offset().top + start;
}() : item.offset().top;
/* 始终只加载在当前屏范围内的图片 */
if(elemTop >= start && elemTop <= end){
if(item.attr('lay-src')){
var src = item.attr('lay-src');
layui.img(src, function(){
var next = that.lazyimg.elem.eq(index);
item.attr('src', src).removeAttr('lay-src');
/* 当前图片加载就绪后,检测下一个图片是否在当前屏 */
next[0] && render(next);
index++;
}, function(){
var next = that.lazyimg.elem.eq(index);
item.removeAttr('lay-src');
});
}
}
}, render = function(othis, scroll){
//计算滚动所在容器的可视高度
var height = notDocment ? (scroll||scrollElem).height() : $(window).height();
var start = scrollElem.scrollTop(), end = start + height;
that.lazyimg.elem = $(elem);
if(othis){
show(othis, height);
} else {
//计算未加载过的图片
for(var i = 0; i < that.lazyimg.elem.length; i++){
var item = that.lazyimg.elem.eq(i), elemTop = notDocment ? function(){
return item.offset().top - scrollElem.offset().top + start;
}() : item.offset().top;
show(item, height);
index = i;
//如果图片的top坐标,超出了当前屏,则终止后续图片的遍历
if(elemTop > end) break;
}
}
};
render();
if(!haveScroll){
var timer;
scrollElem.on('scroll', function(){
var othis = $(this);
if(timer) clearTimeout(timer)
timer = setTimeout(function(){
render(null, othis);
}, 50);
});
haveScroll = true;
}
return render;
};
//暴露接口
exports('flow', new Flow());
});