javascript实现拖放效果

本文实例为大家分享的是一个拖放的效果，参考的代码，重构以下，加以理解学习。

首先来看效果：

拖动div

拖放状态：未开始

【程序说明】

拖动原理：其实就是在拖动块上监听mousedown事件，鼠标点击时，通过事件对象获取对应的坐标参数。然后鼠标移动时再监听document上的mousemove事件，获取鼠标的clientX 和clientY坐标然后设置拖动块的left 和 top。

首先是监听mousedown事件

复制代码代码如下:

 EventUtil.addEventHandler(this.Drag, "mousedown", BindAsEventListener(this, this.Start)); 

然后在Start上添加mousemove 和 mouseup 事件

//监听mousemove 和 mouseup事件
EventUtil.addEventHandler(document, "mousemove", this._fM);
EventUtil.addEventHandler(document, "mouseup", this._fS);

鼠标移动时，设置拖动块的left 和 top 属性：

if(!this.LockX)this.Drag.style.left = iLeft + "px";
 if(!this.LockY)this.Drag.style.top = iTop + "px";

水平和垂直锁定：通过判断LockX 和lockY属性来限制对于的top 和 left 属性即可。

范围限制锁定：通过计算容器的宽高和拖动块的宽高差值来设定最大left值和top值，来限制拖动块的left值和top值会在一定的范围里。

完整DEMO：

<!DOCTYPE html>
<html lang="en">
<head>
 <meta charset="UTF-8">
 <title>JavaScript拖放效果</title>
 <style type="text/css">
  
 </style>
</head>
<body>
 <div id="drag-wrap" style="height: 300px;margin:10px;border:5px solid #FF8000;background:#8080C0;position: relative;">
   <div class="draggable" id="drag" style="width:100px;height: 100px;position: absolute;top: 100px;left:100px;background:#eee;border:1px solid #aceaac;cursor: move;">拖动div</div>
 </div>
 <input id="idReset" type="button" value="复位" />
 <input id="idLock" type="button" value="锁定全部" />
 <input id="idLockX" type="button" value="锁定水平" />
 <input id="idLockY" type="button" value="锁定垂直" />
 <input id="idLimit" type="button" value="范围锁定" />
 <input id="idLimitOff" type="button" value="取消范围锁定" />
 <br />拖放状态：<span id="idShow">未开始</span>
 <script type="text/javascript">
  /**
   *工具函数
   */
   var isIE = (document.all) ? true : false ;
 
   var $$ = function(id){
    return "string" == typeof id ? document.getElementById(id) : id;
   };
 
   var Class = {
   create: function() {
    return function() { this.initialize.apply(this, arguments); }
   }
  };
 
  var Extend = function(destination,source){
   for(var property in source){
    destination[property] = source[property];
   }
  };
 
  var BindAsEventListener = function(object,func){
   return function(event){
    return func.call(object,event || window.event);
   }
  };
 
  var Bind = function(object,func){
   return function(){
    return func.apply(object,arguments);
   }
  };
 
   /**
   *跨浏览器事件对象
   */
  var EventUtil = {
   //事件注册处理程序
   addEventHandler:function(oTarget,sEventType,fnHandler){
     if(oTarget.addEventListener){
      oTarget.addEventListener(sEventType,fnHandler,false);
     }else if(oTarget.attachEvent){
      oTarget.attachEvent("on"+sEventType,fnHandler);
     }else{
      oTarget["on"+sEventType] = fnHandler;
     }
    },
    //事件移除处理程序
    removeEventHandler:function(oTarget,sEventType,fnHandler){
     if(oTarget.removeEventListener){
      oTarget.removeEventListener(sEventType,fnHandler,false);
     }else if(oTarget.detachEvent){
      oTarget.detachEvent("on"+sEventType,fnHandler);
     }else{
      oTarget["on"+sEventType] = null;
     }
    },
    getEvent:function(event){
     return event ? event : window.event;
    },
    getTarget:function(event){
     return event.target || event.srcElement;
    }
  }; 
 
  /**
   *拖放程序
   */
   var Drag= Class.create();
 
   Drag.prototype = {
    //初始化对象
    initialize:function(drag,options){
     this.Drag = $$(drag);//拖放对象
     this._x = this._y = 0;//记录鼠标相对于拖放对象的位置
     //事件对象(用于绑定移除事件)
     this._fM = BindAsEventListener(this, this.Move);
    this._fS = Bind(this, this.Stop);
    this.Drag.style.position = "absolute";
    this.marginLeft = this.marginTop = 0;//记录margin
    //设置参数
    this.setOptions(options);
    //获取相关参数及类型转换
    this.Limit = !!this.options.Limit;//转换为布尔型
    this.mxLeft = parseInt(this.options.mxLeft);
    this.mxRight = parseInt(this.options.mxRight);
    this.mxTop = parseInt(this.options.mxTop);
    this.mxBottom = parseInt(this.options.mxBottom);
 
    this.Lock = !!this.options.Lock;
    this.LockX = !!this.options.LockX;
    this.LockY = !!this.options.LockY;
 
    this.onStart = this.options.onStart;
    this.onMove = this.options.onMove;
    this.onStop = this.options.onStop;
 
    this._Handle = $$(this.options.Handle) || this.Drag;
    this._mxContainer = $$(this.options.mxContainer) || null;
    //监听拖动对象mousedown事件
    EventUtil.addEventHandler(this.Drag, "mousedown", BindAsEventListener(this, this.Start));
 
    },
    //准备拖动 
    Start:function(oEvent){
     if(this.Lock){return;}//如果锁定则不执行
     //记录mousedown触发时鼠标相对于拖放对象的位置
     this._x = oEvent.clientX - this.Drag.offsetLeft;
    this._y = oEvent.clientY - this.Drag.offsetTop;
    //监听mousemove 和 mouseup事件
    EventUtil.addEventHandler(document, "mousemove", this._fM);
    EventUtil.addEventHandler(document, "mouseup", this._fS);
    }, 
    //拖动
    Move:function(oEvent){
     //设置移动参数
     var iLeft = oEvent.clientX - this._x , iTop = oEvent.clientY - this._y;
     //设置范围限制
     if(this.Limit){
      //设置范围参数
     var mxLeft = this.mxLeft, mxRight = this.mxRight, mxTop = this.mxTop, mxBottom = this.mxBottom;
     //如果设置了容器，再修正范围参数
     if(!!this._mxContainer){
      mxLeft = Math.max(mxLeft, 0);
      mxTop = Math.max(mxTop, 0);
      mxRight = Math.min(mxRight, this._mxContainer.clientWidth);
      mxBottom = Math.min(mxBottom, this._mxContainer.clientHeight);
     };
     //修正移动参数
     iLeft = Math.max(Math.min(iLeft, mxRight - this.Drag.offsetWidth), mxLeft);
     iTop = Math.max(Math.min(iTop, mxBottom - this.Drag.offsetHeight), mxTop);
     }
     //XY锁定
     if(!this.LockX)this.Drag.style.left = iLeft + "px";
    if(!this.LockY)this.Drag.style.top = iTop + "px";
    //执行附加程序
    this.onMove();
    },
    //停止拖动
    Stop:function(){
    EventUtil.removeEventHandler(document, "mousemove", this._fM);
    EventUtil.removeEventHandler(document, "mouseup", this._fS);
    //执行附加程序
    this.onStop();
    },
    //设置默认参数
    setOptions:function(options){
     this.options = {//默认值
     Handle:   "",//设置触发对象（不设置则使用拖放对象）
     Limit:   false,//是否设置范围限制(为true时下面参数有用,可以是负数)
     mxLeft:   0,//左边限制
     mxRight:  9999,//右边限制
     mxTop:   0,//上边限制
     mxBottom:  9999,//下边限制
     mxContainer: "",//指定限制在容器内
     LockX:   false,//是否锁定水平方向拖放
     LockY:   false,//是否锁定垂直方向拖放
     Lock:   false,//是否锁定
     Transparent: false,//是否透明
     onStart:  function(){},//开始移动时执行
     onMove:   function(){},//移动时执行
     onStop:   function(){}//结束移动时执行
    };
    Extend(this.options, options || {});
    }
   };
 
  //初始化拖动对象
  var drag = new Drag('drag',{mxContainer:'drag-wrap',Limit:true,
    onStart: function(){ $$("idShow").innerHTML = "开始拖放"; },
    onMove: function(){ $$("idShow").innerHTML = "left："+this.Drag.offsetLeft+"；top:"+this.Drag.offsetTop; },
    onStop: function(){ $$("idShow").innerHTML = "结束拖放"; }
    });
  $$("idReset").onclick = function(){
   drag.Limit = true;
   drag.mxLeft = drag.mxTop = 0;
   drag.mxRight = drag.mxBottom = 9999;
   drag.LockX = drag.LockY = drag.Lock = false;
   $$("idShow").innerHTML = "复位";
  }
  $$("idLock").onclick = function(){ drag.Lock = true;$$("idShow").innerHTML = "锁定全部";}
  $$("idLockX").onclick = function(){ drag.LockX = true; $$("idShow").innerHTML = "锁定水平";}
  $$("idLockY").onclick = function(){ drag.LockY = true; $$("idShow").innerHTML = "锁定垂直";}
  $$("idLimit").onclick = function(){  drag.mxRight = drag.mxBottom = 200;drag.Limit = true;$$("idShow").innerHTML = "范围锁定"; }
  $$("idLimitOff").onclick = function(){ drag.Limit = false; $$("idShow").innerHTML = "取消范围锁定";}
 </script>
</body>
</html>

以上就是javascript实现拖放效果的代码，希望对大家的学习有所帮助。

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javascript实现拖放效果

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