I met a confused problem,I took over a previous Android project.And in the build.gradle,it had already configured the Arcgis for Android version 100.2.1.But in the codes,part of the imports run well and others go wrong,for example:
import com.esri.arcgisruntime.sample.hit.mymap.Utils.MyApplication;
import com.esri.arcgisruntime.sample.hit.R;
import com.esri.arcgisruntime.sample.hit.mymap.Utils.UpdateUtil;
import com.esri.arcgisruntime.sample.hit.mymap.Utils.WebService;
These parts run well.
import com.esri.arcgisruntime.data.ServiceFeatureTable;
import com.esri.arcgisruntime.layers.FeatureLayer;
import com.esri.arcgisruntime.mapping.ArcGISMap;
import com.esri.arcgisruntime.mapping.MobileMapPackage;
import com.esri.arcgisruntime.mapping.view.GraphicsOverlay;
import com.esri.arcgisruntime.mapping.view.LocationDisplay;
import com.esri.arcgisruntime.mapping.view.MapView;
And these parts are marked as errors.The error is "Cant resolve symbol xyz".