大佬们帮忙看看，关于ArcGISTiledMapServiceLayer不显示地图的问题

js中调用new esri.layers.ArcGISTiledMapServiceLayer(url,{})，不显示地图，只显示标尺
代码如下
dojo.declare("esri.layers.ArcGISTiledMapServiceLayer", [esri.layers.TiledMapServiceLayer, esri.layers.ArcGISMapServiceLayer], {
            constructor: function(url, _5b1){
debugger;
                if (_5b1) {
                    if (_5b1.roundrobin) {
                        dojo.deprecated(this.declaredClass + " : " + esri.bundle.layers.agstiled.deprecateRoundrobin);
                        _5b1.tileServers = _5b1.roundrobin;
                    }
                    var ts = (this.tileServers = _5b1.tileServers);
                    if (ts) {
                        if (ts.length === 0) {
                            ts = null;
                        }
                        else {
                            for (var i = 0, il = ts.length; i < il; i++) {
                                ts[i] = esri.urlToObject(ts[i]).path;
                            }
                        }
                    }
                }
                this._params = dojo.mixin({}, this._url.query);
                this.tsi = 0;
debugger;
                this._initLayer = dojo.hitch(this, this._initLayer);
                this._load = dojo.hitch(this, this._load);
                this._load();
            },
            _TILE_FORMATS: {
                PNG: "png",
                PNG8: "png",
                PNG24: "png",
                PNG32: "png",
                JPG: "jpg",
                JPEG: "jpg",
                GIF: "gif"
            },
            _initLayer: function(_5b2, io){
debugger;
                this.inherited(arguments);
                this.tileInfo = new esri.layers.TileInfo(_5b2.tileInfo);
                this._tileFormat = this._TILE_FORMATS[this.tileInfo.format];
                this.isPNG32 = this.tileInfo.format === "PNG24" || this.tileInfo.format === "PNG32";
                this.loaded = true;
                this.onLoad(this);
            },
            getTileUrl: function(_5b3, row, col){
                var ts = this.tileServers, iurl = (ts ? ts[this.tsi++ % ts.length] : this._url.path) + "/tile/" + _5b3 + "/" + row + "/" + col + "." + this._tileFormat;
                if (this._url.query) {
                    iurl += ("?" + dojo.objectToQuery(this._url.query));
                }
                return esri._getProxiedUrl(iurl);
            }
        });