《JavaScript 实战》：实现拖放（Drag & Drop）效果

　　拖放效果，也叫拖拽、拖动，学名Drag-and-drop ，是最常见的js特效之一。如果忽略很多细节，实现起来很简单，但往往细节才是难点所在。这个程序的原型是在做图片切割效果的时候做出来的，那时参考了好几个同类的效果，跟muxrwc和BlueDestiny学习了不少东西。

　　虽然每次整理都觉得很好了，不过每隔一段时间又会发现得某个地方可以改善，某个地方有错误，某些需求需要实现，就像自己学习的知识那样。

　　这里考虑到有的人可能只需要简单的拖放，所以有一个简化版的拖放SimpleDrag，方便学习。

效果预览

ps：在maxthon下如果开启广告过滤的话很可能会被过滤掉（不知有什么方法可以避免）。

// 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 Bind = function(object, fun) {
return function() {
return fun.apply(object, arguments);
}
}

var BindAsEventListener = function(object, fun) {
return function(event) {
return fun.call(object, (event || window.event));
}
}

var CurrentStyle = function(element){
return element.currentStyle || document.defaultView.getComputedStyle(element, null);
}

function addEventHandler(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;
}
};

function removeEventHandler(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;
}
};

//拖放程序
var Drag = Class.create();
Drag.prototype = {
//拖放对象
initialize: function(drag, options) {
this.Drag = $$(drag);//拖放对象
this._x = this._y = 0;//记录鼠标相对拖放对象的位置
this._marginLeft = this._marginTop = 0;//记录margin
//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.SetOptions(options);

this.Limit = !!this.options.Limit;
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.LockX = !!this.options.LockX;
this.LockY = !!this.options.LockY;
this.Lock = !!this.options.Lock;

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;

this.Drag.style.position = "absolute";
//透明
if(isIE && !!this.options.Transparent){
//ie6渲染bug
this._Handle.style.overflow = "hidden";
//填充拖放对象
with(this._Handle.appendChild(document.createElement("div")).style){
width = height = "100%"; backgroundColor = "#fff"; filter = "alpha(opacity:0)";
}
}
//修正范围
this.Repair();
addEventHandler(this._Handle, "mousedown", BindAsEventListener(this, this.Start));
},
//设置默认属性
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 || {});
},
//准备拖动
Start: function(oEvent) {
if(this.Lock){ return; }
this.Repair();
//记录鼠标相对拖放对象的位置
this._x = oEvent.clientX - this.Drag.offsetLeft;
this._y = oEvent.clientY - this.Drag.offsetTop;
//记录margin
this._marginLeft = parseInt(CurrentStyle(this.Drag).marginLeft) || 0;
this._marginTop = parseInt(CurrentStyle(this.Drag).marginTop) || 0;
//mousemove时移动 mouseup时停止
addEventHandler(document, "mousemove", this._fM);
addEventHandler(document, "mouseup", this._fS);
if(isIE){
//焦点丢失
addEventHandler(this._Handle, "losecapture", this._fS);
//设置鼠标捕获
this._Handle.setCapture();
}else{
//焦点丢失
addEventHandler(window, "blur", this._fS);
//阻止默认动作
oEvent.preventDefault();
};
//附加程序
this.onStart();
},
//修正范围
Repair: function() {
if(this.Limit){
//修正错误范围参数
this.mxRight = Math.max(this.mxRight, this.mxLeft + this.Drag.offsetWidth);
this.mxBottom = Math.max(this.mxBottom, this.mxTop + this.Drag.offsetHeight);
//如果有容器必须设置position为relative来相对定位，并在获取offset之前设置
!this._mxContainer || CurrentStyle(this._mxContainer).position == "relative" || (this._mxContainer.style.position = "relative");
}
},
//拖动
Move: function(oEvent) {
//判断是否锁定
if(this.Lock){ this.Stop(); return; };
//清除选择
window.getSelection ? window.getSelection().removeAllRanges() : document.selection.empty();
//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);
}
//设置位置，并修正margin
if(!this.LockX){ this.Drag.style.left = iLeft - this._marginLeft + "px"; }
if(!this.LockY){ this.Drag.style.top = iTop - this._marginTop + "px"; }
//附加程序
this.onMove();
},
//停止拖动
Stop: function() {
//移除事件
removeEventHandler(document, "mousemove", this._fM);
removeEventHandler(document, "mouseup", this._fS);
if(isIE){
removeEventHandler(this._Handle, "losecapture", this._fS);
this._Handle.releaseCapture();
}else{
removeEventHandler(window, "blur", this._fS);
};
//附加程序
this.onStop();
}
};
// ]]>

拖放状态：未开始
// var drag = new Drag("idDrag", { mxContainer: "idContainer", Handle: "idHandle", 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;
}

$$("idLock").onclick = function(){ drag.Lock = true; }
$$("idLockX").onclick = function(){ drag.LockX = true; }
$$("idLockY").onclick = function(){ drag.LockY = true; }
$$("idLimit").onclick = function(){ drag.mxRight = drag.mxBottom = 200;drag.Limit = true; }
$$("idLimitOff").onclick = function(){ drag.Limit = false; }
// ]]>

程序说明

【程序原理】

这里以SimpleDrag为例说一下基本原理。

首先初始化程序中要一个拖放对象：

//拖放程序
var Drag = Class.create();
Drag.prototype = {
//拖放对象
initialize: function(drag, options) {
this.Drag = $(drag);//拖放对象
this._x = this._y = 0;//记录鼠标相对拖放对象的位置
this._marginLeft = this._marginTop = 0;//记录margin
//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.SetOptions(options);

this.Limit = !!this.options.Limit;
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.LockX = !!this.options.LockX;
this.LockY = !!this.options.LockY;
this.Lock = !!this.options.Lock;

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;

this.Drag.style.position = "absolute";
//透明
if(isIE && !!this.options.Transparent){
//填充拖放对象
with(this._Handle.appendChild(document.createElement("div")).style){
width = height = "100%"; backgroundColor = "#fff"; filter = "alpha(opacity:0)"; fontSize = 0;
}
}
//修正范围
this.Repair();
addEventHandler(this._Handle, "mousedown", BindAsEventListener(this, this.Start));
},
//设置默认属性
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 || {});
},
//准备拖动
Start: function(oEvent) {
if(this.Lock){ return; }
this.Repair();
//记录鼠标相对拖放对象的位置
this._x = oEvent.clientX - this.Drag.offsetLeft;
this._y = oEvent.clientY - this.Drag.offsetTop;
//记录margin
this._marginLeft = parseInt(CurrentStyle(this.Drag).marginLeft) || 0;
this._marginTop = parseInt(CurrentStyle(this.Drag).marginTop) || 0;
//mousemove时移动 mouseup时停止
addEventHandler(document, "mousemove", this._fM);
addEventHandler(document, "mouseup", this._fS);
if(isIE){
//焦点丢失
addEventHandler(this._Handle, "losecapture", this._fS);
//设置鼠标捕获
this._Handle.setCapture();
}else{
//焦点丢失
addEventHandler(window, "blur", this._fS);
//阻止默认动作
oEvent.preventDefault();
};
//附加程序
this.onStart();
},
//修正范围
Repair: function() {
if(this.Limit){
//修正错误范围参数
this.mxRight = Math.max(this.mxRight, this.mxLeft + this.Drag.offsetWidth);
this.mxBottom = Math.max(this.mxBottom, this.mxTop + this.Drag.offsetHeight);
//如果有容器必须设置position为relative来相对定位，并在获取offset之前设置
!this._mxContainer || CurrentStyle(this._mxContainer).position == "relative" || (this._mxContainer.style.position = "relative");
}
},
//拖动
Move: function(oEvent) {
//判断是否锁定
if(this.Lock){ this.Stop(); return; };
//清除选择
window.getSelection ? window.getSelection().removeAllRanges() : document.selection.empty();
//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);
}
//设置位置，并修正margin
if(!this.LockX){ this.Drag.style.left = iLeft - this._marginLeft + "px"; }
if(!this.LockY){ this.Drag.style.top = iTop - this._marginTop + "px"; }
//附加程序
this.onMove();
},
//停止拖动
Stop: function() {
//移除事件
removeEventHandler(document, "mousemove", this._fM);
removeEventHandler(document, "mouseup", this._fS);
if(isIE){
removeEventHandler(this._Handle, "losecapture", this._fS);
this._Handle.releaseCapture();
}else{
removeEventHandler(window, "blur", this._fS);
};
//附加程序
this.onStop();
}
};

完整实例下载

本文链接：/article/6368940.html

原文出处：cloudgamer