首先是转载，地址：http://jaychaoqun.javaeye.com/blog/392110
接下来是理解之后的实例
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> |
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<html xmlns="http://www.w3.org/1999/xhtml"> |
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<head> |
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> |
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<title>简易拖放效果</title> |
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</head> |
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<body> |
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<script> |
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//参考：http://www.javaeye.com/topic/57760 |
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|
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//简化id选择器 |
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var isIE = (document.all) ? true : false; |
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var $ = function (id) { |
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return "string" == typeof id ? document.getElementById(id) : id; |
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}; |
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|
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//初始化一个 Class 对象， 它有一个成员，是一个方法， 这个方法返因另一个方法（方法是对象，所以可以作为参数或者返回值） |
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var Class = { |
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create: function() { |
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return function() { //使用new操作符时，就会在新产生的对象上调用这个方法 |
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this.initialize.apply(this, arguments); //这里就是调用 this 对象上的 initialize方法， 并传递 arguments，这里的this是new之后构造出来的对象 |
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} |
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} |
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} |
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|
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//继承，这里没有用到 |
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var Extend = function(destination, source) { |
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for (var property in source) { |
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destination[property] = source[property]; |
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} |
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} |
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|
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//参数传递 |
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//object参数，fun方法 |
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var Bind = function(object, fun) { |
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return function() { |
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return fun.apply(object, arguments); |
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} |
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} |
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|
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//事件传递 |
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//object参数，fun方法 |
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var BindAsEventListener = function(object, fun) { |
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return function(event) { |
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return fun.call(object, (event || window.event)); |
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} |
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} |
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|
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//事件绑定 |
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//oTarget绑定目标，sEventType事件类型，fnHandler事件方法 |
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function addEventHandler(oTarget, sEventType, fnHandler) { |
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if (oTarget.addEventListener) { //FF |
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oTarget.addEventListener(sEventType, fnHandler, false); |
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} else if (oTarget.attachEvent) { //IE |
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oTarget.attachEvent("on" + sEventType, fnHandler); |
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} else { |
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oTarget["on" + sEventType] = fnHandler; |
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} |
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}; |
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|
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//移除事件绑定 |
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//oTarget绑定目标，sEventType事件类型，fnHandler事件方法 |
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function removeEventHandler(oTarget, sEventType, fnHandler) { |
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if (oTarget.removeEventListener) { //FF |
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oTarget.removeEventListener(sEventType, fnHandler, false); |
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} else if (oTarget.detachEvent) { //IE |
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oTarget.detachEvent("on" + sEventType, fnHandler); |
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} else { |
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oTarget["on" + sEventType] = null; |
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} |
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}; |
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|
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//SimpleDrag是一个方法，方法体，这里相当于一个类 |
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var SimpleDrag = Class.create(); |
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SimpleDrag.prototype = { |
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//对象初始化，实现Class中的this.initialize |
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initialize: function(drag) { |
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this.Drag = $(drag); //绑定目标 |
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this._x = this._y = 0; //初始值 |
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this._fnMove = BindAsEventListener(this, this.Move); |
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this._fnStop = Bind(this, this.Stop); |
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this.Drag.style.position = "absolute"; |
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addEventHandler(this.Drag, "mousedown", BindAsEventListener(this, this.Start));//监听鼠标按下事件 |
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}, |
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//准备拖动 |
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Start: function(oEvent) { |
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this._x = oEvent.clientX - this.Drag.offsetLeft; |
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this._y = oEvent.clientY - this.Drag.offsetTop; |
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addEventHandler(document, "mousemove", this._fnMove); //对象开始拖动后，监听鼠标移动事件 |
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addEventHandler(document, "mouseup", this._fnStop); //同时监听鼠标放开事件 |
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}, |
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//拖动 |
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Move: function(oEvent) { |
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this.Drag.style.left = oEvent.clientX - this._x + "px"; |
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this.Drag.style.top = oEvent.clientY - this._y + "px"; |
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}, |
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//停止拖动 |
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Stop: function() { |
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removeEventHandler(document, "mousemove", this._fnMove); |
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removeEventHandler(document, "mouseup", this._fnStop); |
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} |
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}; |
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</script> |
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<div id="idDrag" style="border:5px solid #0000FF; background:#C4E3FD; width:50px; height:50px;"></div> |
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<script> |
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new SimpleDrag("idDrag"); |
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</script> |
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</body> |
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</html> |
