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Detailed explanation of JavaScript implementation of proportional drag and zoom method of selection box
Detailed explanation of JavaScript implementation of proportional drag and zoom method of selection box
本文实例讲述了JavaScript实现选择框按比例拖拉缩放的方法。分享给大家供大家参考。具体如下：
这里通过javascript实现可以像PS一样拉出一个选择框的效果。里面的很多方法都是我们值得学习的。
运行效果如下图所示：
具体代码如下：
<!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>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>JavaScript拖拉缩放效果</title>
</head>
<body>
<script>
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) {
var args = Array.prototype.slice.call(arguments).slice(2);
return function(event) {
return fun.apply(object, [event || window.event].concat(args));
}
}
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;
}
};
//缩放程序
var Resize = Class.create();
Resize.prototype = {
//缩放对象
initialize: function(obj, options) {
this._obj = $(obj);//缩放对象
this._styleWidth = this._styleHeight = this._styleLeft = this._styleTop = 0;//样式参数
this._sideRight = this._sideDown = this._sideLeft = this._sideUp = 0;//坐标参数
this._fixLeft = this._fixTop = 0;//定位参数
this._scaleLeft = this._scaleTop = 0;//定位坐标
this._mxSet = function(){};//范围设置程序
this._mxRightWidth = this._mxDownHeight = this._mxUpHeight = this._mxLeftWidth = 0;//范围参数
this._mxScaleWidth = this._mxScaleHeight = 0;//比例范围参数
this._fun = function(){};//缩放执行程序
//获取边框宽度
var _style = CurrentStyle(this._obj);
this._borderX = (parseInt(_style.borderLeftWidth) || 0) + (parseInt(_style.borderRightWidth) || 0);
this._borderY = (parseInt(_style.borderTopWidth) || 0) + (parseInt(_style.borderBottomWidth) || 0);
//事件对象(用于绑定移除事件)
this._fR = BindAsEventListener(this, this.Resize);
this._fS = Bind(this, this.Stop);
this.SetOptions(options);
//范围限制
this.Max = !!this.options.Max;
this._mxContainer = $(this.options.mxContainer) || null;
this.mxLeft = Math.round(this.options.mxLeft);
this.mxRight = Math.round(this.options.mxRight);
this.mxTop = Math.round(this.options.mxTop);
this.mxBottom = Math.round(this.options.mxBottom);
//宽高限制
this.Min = !!this.options.Min;
this.minWidth = Math.round(this.options.minWidth);
this.minHeight = Math.round(this.options.minHeight);
//按比例缩放
this.Scale = !!this.options.Scale;
this.Ratio = Math.max(this.options.Ratio, 0);
this.onResize = this.options.onResize;
this._obj.style.position = "absolute";
!this._mxContainer || CurrentStyle(this._mxContainer).position == "relative" || (this._mxContainer.style.position = "relative");
},
//设置默认属性
SetOptions: function(options) {
this.options = {//默认值
Max: false,//是否设置范围限制(为true时下面mx参数有用)
mxContainer:"",//指定限制在容器内
mxLeft: 0,//左边限制
mxRight: 9999,//右边限制
mxTop: 0,//上边限制
mxBottom: 9999,//下边限制
Min: false,//是否最小宽高限制(为true时下面min参数有用)
minWidth: 50,//最小宽度
minHeight: 50,//最小高度
Scale: false,//是否按比例缩放
Ratio: 0,//缩放比例(宽/高)
onResize: function(){}//缩放时执行
};
Extend(this.options, options || {});
},
//设置触发对象
Set: function(resize, side) {
var resize = $(resize), fun;
if(!resize) return;
//根据方向设置
switch (side.toLowerCase()) {
case "up" :
fun = this.Up;
break;
case "down" :
fun = this.Down;
break;
case "left" :
fun = this.Left;
break;
case "right" :
fun = this.Right;
break;
case "left-up" :
fun = this.LeftUp;
break;
case "right-up" :
fun = this.RightUp;
break;
case "left-down" :
fun = this.LeftDown;
break;
case "right-down" :
default :
fun = this.RightDown;
};
//设置触发对象
addEventHandler(resize, "mousedown", BindAsEventListener(this, this.Start, fun));
},
//准备缩放
Start: function(e, fun, touch) {
//防止冒泡(跟拖放配合时设置)
e.stopPropagation ? e.stopPropagation() : (e.cancelBubble = true);
//设置执行程序
this._fun = fun;
//样式参数值
this._styleWidth = this._obj.clientWidth;
this._styleHeight = this._obj.clientHeight;
this._styleLeft = this._obj.offsetLeft;
this._styleTop = this._obj.offsetTop;
//四条边定位坐标
this._sideLeft = e.clientX - this._styleWidth;
this._sideRight = e.clientX + this._styleWidth;
this._sideUp = e.clientY - this._styleHeight;
this._sideDown = e.clientY + this._styleHeight;
//top和left定位参数
this._fixLeft = this._styleLeft + this._styleWidth;
this._fixTop = this._styleTop + this._styleHeight;
//缩放比例
if(this.Scale){
//设置比例
this.Ratio = Math.max(this.Ratio, 0) || this._styleWidth / this._styleHeight;
//left和top的定位坐标
this._scaleLeft = this._styleLeft + this._styleWidth / 2;
this._scaleTop = this._styleTop + this._styleHeight / 2;
};
//范围限制
if(this.Max){
//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);
};
//根据最小值再修正
mxRight = Math.max(mxRight, mxLeft + (this.Min ? this.minWidth : 0) + this._borderX);
mxBottom = Math.max(mxBottom, mxTop + (this.Min ? this.minHeight : 0) + this._borderY);
//由于转向时要重新设置所以写成function形式
this._mxSet = function(){
this._mxRightWidth = mxRight - this._styleLeft - this._borderX;
this._mxDownHeight = mxBottom - this._styleTop - this._borderY;
this._mxUpHeight = Math.max(this._fixTop - mxTop, this.Min ? this.minHeight : 0);
this._mxLeftWidth = Math.max(this._fixLeft - mxLeft, this.Min ? this.minWidth : 0);
};
this._mxSet();
//有缩放比例下的范围限制
if(this.Scale){
this._mxScaleWidth = Math.min(this._scaleLeft - mxLeft, mxRight - this._scaleLeft - this._borderX) * 2;
this._mxScaleHeight = Math.min(this._scaleTop - mxTop, mxBottom - this._scaleTop - this._borderY) * 2;
};
};
//mousemove时缩放 mouseup时停止
addEventHandler(document, "mousemove", this._fR);
addEventHandler(document, "mouseup", this._fS);
if(isIE){
addEventHandler(this._obj, "losecapture", this._fS);
this._obj.setCapture();
}else{
addEventHandler(window, "blur", this._fS);
e.preventDefault();
};
},
//缩放
Resize: function(e) {
//清除选择
window.getSelection ? window.getSelection().removeAllRanges() : document.selection.empty();
//执行缩放程序
this._fun(e);
//设置样式，变量必须大于等于0否则ie出错
with(this._obj.style){
width = this._styleWidth + "px"; height = this._styleHeight + "px";
top = this._styleTop + "px"; left = this._styleLeft + "px";
}
//附加程序
this.onResize();
},
//缩放程序
//上
Up: function(e) {
this.RepairY(this._sideDown - e.clientY, this._mxUpHeight);
this.RepairTop();
this.TurnDown(this.Down);
},
//下
Down: function(e) {
this.RepairY(e.clientY - this._sideUp, this._mxDownHeight);
this.TurnUp(this.Up);
},
//右
Right: function(e) {
this.RepairX(e.The above is the detailed content of Detailed explanation of JavaScript implementation of proportional drag and zoom method of selection box. For more information, please follow other related articles on the PHP Chinese website!
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