E/ArcGIS: No data tile ETag couldn't be retrieved这个到底是什么错？

11-04 19:21:43.165 14331-14864/cn.fygis.liuwugis E/ArcGIS: No data tile ETag couldn't be retrieved
com.esri.core.io.EsriServiceException: Not Found
at com.esri.core.internal.io.handler.c.a(SourceFile:690)
at com.esri.core.internal.io.handler.a.a(SourceFile:87)
at com.esri.core.internal.tasks.ags.an.a(SourceFile:36)
at com.esri.android.map.ags.ArcGISTiledMapServiceLayer.retrieveNoDataTileETag(SourceFile:570)
at com.esri.android.map.ags.ArcGISTiledMapServiceLayer.initLayer(SourceFile:201)
at com.esri.android.map.ags.ArcGISTiledMapServiceLayer$1.run(SourceFile:132)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:423)
at java.util.concurrent.FutureTask.run(FutureTask.java:237)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)
at java.lang.Thread.run(Thread.java:818)