arcgis api for javascript如何根据经纬度进行标注，类似百度地图的Marker标注功能，代码越简单详细越好，谢谢各位了

var symbol = new esri.symbol.PictureMarkerSymbol(getRootPath() + "content/images/ems/WZCBD.png", 24, 24);//图片设置

//设置气泡窗口内容

var title = "测试";

var htmlstr = "测试内容";

var attr = { "title": title, "content": htmlstr};            	

var pt = new esri.geometry.Point(111.456,23.456,map.spatialReference);

var graphic = new esri.Graphic(pt, symbol, attr);		                	   

ems.resource.graphicslayer.add(graphic);

//显示气泡窗口

ems.resource.map.centerAt(pt);

ems.resource.map.infoWindow.resize(420, 650);

ems.resource.map.infoWindow.show(pt);