实现网页地图上的动态多边形绘制

/**
 * 开始画多边形实例
 * @class GDrawPolygonControl
 */
var CDrawPolygonBaseControl = {
_attachDrawPolygonEvents: function (){
if( !this.moveoutDrawPolygonFlagFunc ) {
this.moveoutDrawPolygonFlagFunc = this.moveoutDrawPolygonFlag.bindAsEventListener(this);
Event.observe(this.map.domObj, 'mouseout', this.moveoutDrawPolygonFlagFunc, false);
}
if( !this.moveDrawPolygonFlagFunc ) {
this.moveDrawPolygonFlagFunc = this.moveDrawPolygonFlag.bindAsEventListener(this);
Event.observe(this.map.domObj, 'mousemove', this.moveDrawPolygonFlagFunc, true);
}
if( !this.onDrawPolygonClickFunc )
this.onDrawPolygonClickFunc = CEvent.addListener(this.map, "click",  this.onDrawPolygonClick.bind(this));
 
 
Event.observe(this.map.domObj, 'dblclick', this.onDrawPolygonEnd.bindAsEventListener(this));

},
_detachDrawPolygonEvents: function (){
if( this.moveoutDrawPolygonFlagFunc ) {
Event.stopObserving(this.map.domObj, 'mouseout', this.moveoutDrawPolygonFlagFunc, false);
this.moveoutDrawPolygonFlagFunc = null;
}
if( this.moveDrawPolygonFlagFunc ) {
Event.stopObserving(this.map.domObj, 'mousemove', this.moveDrawPolygonFlagFunc, true);
this.moveDrawPolygonFlagFunc = null;

}
if( this.onDrawPolygonClickFunc ) {
CEvent.removeListener(this.onDrawPolygonClickFunc);
this.onDrawPolygonClickFunc = null;
}
this.map.onDoubleClickForDrawPolygon = null;
},
onDrawPolygon:function (){

this.areaRemoveable = this.map.disableSpotLoader();
if( !this.DrawPolygonImg ) {
this.DrawPolygonImg = document.createElement( 'img' );
this.DrawPolygonImg.id = 'drawPolygonFlag';
this.DrawPolygonImg.src = CCommon.mapKernelServer()+'images/console/flag.gif';
this.DrawPolygonImg.onmousemove = this.moveDrawPolygonFlag.bindAsEventListener(this);
document.body.appendChild( this.DrawPolygonImg );
}
if( !this.DrawPolygonTip ) {
this.DrawPolygonTip = document.createElement( 'div' );
this.DrawPolygonTip.id = 'DrawPolygonTip';
this.DrawPolygonTip.setAttribute("className", "tip");
this.DrawPolygonTip.setAttribute("class", "tip");
this.DrawPolygonTip.innerHTML = '单击开始画图,双击结束';
this.DrawPolygonTip.onmousemove = this.moveDrawPolygonFlag.bindAsEventListener(this);
document.body.appendChild( this.DrawPolygonTip );
}
this._attachDrawPolygonEvents();
this.DrawPolygonImg.style.position = 'absolute';
this.DrawPolygonImg.style.visibility = 'hidden';
},