arcgis如何加载离线包

Question

    val tileCache = TileCache(Environment.getExternalStorageDirectory().absolutePath +"/"+ getString(R.string.tpk_path))
    val tiledLayer = ArcGISTiledLayer(tileCache)
    mapView.map = ArcGISMap(Basemap(tiledLayer))
    Log.e(TAG,tileCache.path)

以上代码加载后地图毫无反应，tpk文件为官网下载的streetmap_SD.tpk