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/// <reference name="MicrosoftAjax.js"/>

Type.registerNamespace("DDT");

DDT.CityButton 

= function(element) {
    DDT.CityButton.initializeBase(this, [element]);
    this.cityDiv;
}

DDT.CityButton.prototype 

= {
    initialize: function() {
        DDT.CityButton.callBaseMethod(this, 'initialize');
        this._onMouseOverHandler = Function.createDelegate(this,this._onMouseOver);
        this._onMouseOutHandler = Function.createDelegate(this,this._onMouseOut);
        $addHandler(this.get_element(), "mouseover",this._onMouseOverHandler);
        $addHandler(this.get_element(), "mouseout",this._onMouseOutHandler);   
        $addHandler(this.cityDiv, "mouseout",this._onMouseOutHandler);  
        $addHandler(this.cityDiv, "mouseover",this._onMouseOverHandler);   
    },
    get_cityDiv : function() {return this.cityDiv;},
    set_cityDiv : function(value) {  
        if (this.cityDiv != value) {   
                this.cityDiv = value;
                this.raisePropertyChanged("cityDiv");
            }
    },
    _onMouseOver:function(){
        var Bounds = Sys.UI.DomElement.getBounds(this.get_element());
        var x = Bounds.x;
        var y = Bounds.height+Bounds.y;
        Sys.UI.DomElement.setLocation(this.cityDiv,x,y);
        Sys.UI.DomElement.setVisible(this.cityDiv,true);
    },
    _onMouseOut:function(){
        Sys.UI.DomElement.setVisible(this.cityDiv,false);
    },
    dispose: function() {        
        //Add custom dispose actions here
        DDT.CityButton.callBaseMethod(this, 'dispose');
    }
}
DDT.CityButton.registerClass('DDT.CityButton', Sys.UI.Behavior);if (typeof(Sys) !== 'undefined') Sys.Application.notifyScriptLoaded();

使用方法：

      $create(DDT.CityButton,{"cityDiv":$get("Layer1")},null,null,$get("btn"));