OpenLayers叠加天地图矢量、影像、注记

* @description getArcgisXYZTileTD XYZ构造天地图底图

* @param {Object} item 图层对象，包涵url、id

* @param {Object} olmap 地图对象

* @param {Number} zindex 层级

*/

var getArcgisXYZTileTD = (item , zindex , olmap) =>{

        var layer = new olmap.layer.Tile({

                id: item.id,

                zIndex: zindex,

                source: new olmap.source.XYZ({

                        url: item.url,

                        crossOrigin: 'anonymous' //防止地图打印出现问题

                })

        })

        return layer

}