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asp.net 图片延迟加载（参考别人写的案例实验一下）

2012-04-26 15:22 363 查看

方法1
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm43.aspx.cs" Inherits="jquerytest.WebForm43" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title></title>

<script src="jquery-1.4.1-vsdoc.js" type="text/javascript"></script>
<script src="js/jquery.lazyload.js" type="text/javascript"></script>
</head>
<body>
<form id="form1" runat="server">
<div>
<img src="Image/1/grey.gif"  alt="" original="Image/1/IMG_0202.jpg" />
<img src="Image/1/grey.gif"  alt="" original="Image/1/IMG_0208.jpg" />
</div>
</form>
</body>
</html>

<script language="javascript" type="text/javascript">
$(function() {
$("img[original]").lazyload({
placeholder: "Image/1/grey.gif",
effect: "fadeIn"
});
});
</script>

方法2

<img src=""  alt="" original="Image/1/IMG_0202.jpg" />

lazyload.js

/*
* Lazy Load - jQuery plugin for lazy loading images
*
* Copyright (c) 2007-2009 Mika Tuupola
*
* Licensed under the MIT license:
*   http://www.opensource.org/licenses/mit-license.php *
* Project home:
*   http://www.appelsiini.net/projects/lazyload *
* Version:  1.5.0
*
*/
(function ($) {

$.fn.lazyload = function (options) {
var settings = {
threshold: 0,
failurelimit: 0,
event: "scroll",
effect: "show",
container: window
};

if (options) {
$.extend(settings, options);
}

/* Fire one scroll event per scroll. Not one scroll event per image. */
var elements = this;
if ("scroll" == settings.event) {
$(settings.container).bind("scroll", function (event) {

var counter = 0;
elements.each(function () {
if ($.abovethetop(this, settings) ||
$.leftofbegin(this, settings)) {
/* Nothing. */
} else if (!$.belowthefold(this, settings) &&
!$.rightoffold(this, settings)) {
$(this).trigger("appear");
} else {
if (counter++ > settings.failurelimit) {
return false;
}
}
});
/* Remove image from array so it is not looped next time. */
var temp = $.grep(elements, function (element) {
return !element.loaded;
});
elements = $(temp);
});
}

this.each(function () {
var self = this;

/* Save original only if it is not defined in HTML.
if (undefined == $(self).attr("original")) {
$(self).attr("original", $(self).attr("src"));
}*/

if ("scroll" != settings.event ||
undefined == $(self).attr("src") ||
settings.placeholder == $(self).attr("src") ||
($.abovethetop(self, settings) ||
$.leftofbegin(self, settings) ||
$.belowthefold(self, settings) ||
$.rightoffold(self, settings))) {

if (settings.placeholder) {
$(self).attr("src", settings.placeholder);
} else {
$(self).removeAttr("src");
}
self.loaded = false;
} else {
self.loaded = true;
}

/* When appear is triggered load original image. */
$(self).one("appear", function () {
if (!this.loaded) {
$("<img />")
.bind("load", function () {
if ($(self).attr("descImage") != null) {
$(self).attr("style", "overflow:hidden; width:500px; margin-left:105px; margin-top:10px;");
}
$(self).hide().attr("src", $(self).attr("original"))[settings.effect](settings.effectspeed);
self.loaded = true;
})
.attr("src", $(self).attr("original"));
};
});

/* When wanted event is triggered load original image */
/* by triggering appear.                              */
if ("scroll" != settings.event) {
$(self).bind(settings.event, function (event) {
if (!self.loaded) {
$(self).trigger("appear");
}
});
}
});

/* Force initial check if images should appear. */
$(settings.container).trigger(settings.event);

return this;

};

/* Convenience methods in jQuery namespace.           */
/* Use as  $.belowthefold(element, {threshold : 100, container : window}) */

$.belowthefold = function (element, settings) {
if (settings.container === undefined || settings.container === window) {
var fold = $(window).height() + $(window).scrollTop();
} else {
var fold = $(settings.container).offset().top + $(settings.container).height();
}
return fold <= $(element).offset().top - settings.threshold;
};

$.rightoffold = function (element, settings) {
if (settings.container === undefined || settings.container === window) {
var fold = $(window).width() + $(window).scrollLeft();
} else {
var fold = $(settings.container).offset().left + $(settings.container).width();
}
return fold <= $(element).offset().left - settings.threshold;
};

$.abovethetop = function (element, settings) {
if (settings.container === undefined || settings.container === window) {
var fold = $(window).scrollTop();
} else {
var fold = $(settings.container).offset().top;
}
return fold >= $(element).offset().top + settings.threshold + $(element).height();
};

$.leftofbegin = function (element, settings) {
if (settings.container === undefined || settings.container === window) {
var fold = $(window).scrollLeft();
} else {
var fold = $(settings.container).offset().left;
}
return fold >= $(element).offset().left + settings.threshold + $(element).width();
};
/* Custom selectors for your convenience.   */
/* Use as $("img:below-the-fold").something() */

$.extend($.expr[':'], {
"below-the-fold": "$.belowthefold(a, {threshold : 0, container: window})",
"above-the-fold": "!$.belowthefold(a, {threshold : 0, container: window})",
"right-of-fold": "$.rightoffold(a, {threshold : 0, container: window})",
"left-of-fold": "!$.rightoffold(a, {threshold : 0, container: window})"
});

})(jQuery);

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