Arcgis api for javascript 图层的获取与更替

……

var landusePointLayer = new esri.layers.FeatureLayer("http://10.0.0.28/arcgis/rest/services/editFeature/FeatureServer/0", {
mode: esri.layers.FeatureLayer.MODE_ONDEMAND,
outFields: ["*"],
id: "HotspotLayer"
});
map.addLayers([landusePointLayer]);

……
//直接获取指明的layer
var featureHotspotLayer = map.getLayer("HotspotLayer");
var featurelayers=map.getLayer(map.layerIds[2]);
map.removeLayer(map.getLayer(map.layerIds[0]));

//例子，更替底图层
function mapBaseEsri(){
dojo.addOnLoad(function(){
map.removeLayer(map.getLayer(map.layerIds[2]));
tiledMapServiceLayer = new esri.layers.ArcGISTiledMapServiceLayer("http://server.arcgisonline.com/ArcGIS/rest/services/World_Imagery/MapServer");
map.addLayer(tiledMapServiceLayer);
});
}

//全局变量
var basemap1 ;

function getlsLayer(){
dojo.addOnLoad(function(){
basemap1 = new esri.layers.ArcGISDynamicMapServiceLayer("http://mapservice.agrolib.com/ArcGIS/rest/services/wl_ChinaBasicMap/MapServer");
map.addLayer(basemap1);
   });
}

function lsClearClick(){//removerlsLayer(){
dojo.addOnLoad(function(){
map.reorderLayer(basemap1);
});
}