Convert MapController to kotlin along with fixing nullability in a few places

app/src/main/java/fr/free/nrw/commons/MapController.java

@@ -1,30 +0,0 @@
-package fr.free.nrw.commons;
-
-import fr.free.nrw.commons.location.LatLng;
-import fr.free.nrw.commons.nearby.Place;
-import java.util.List;
-
-public abstract class MapController {
-
-    /**
-     * We pass this variable as a group of placeList and boundaryCoordinates
-     */
-    public class NearbyPlacesInfo {
-        public List<Place> placeList; // List of nearby places
-        public LatLng[] boundaryCoordinates; // Corners of nearby area
-        public LatLng currentLatLng; // Current location when this places are populated
-        public LatLng searchLatLng; // Search location for finding this places
-        public List<Media> mediaList; // Search location for finding this places
-    }
-
-    /**
-     * We pass this variable as a group of placeList and boundaryCoordinates
-     */
-    public class ExplorePlacesInfo {
-        public List<Place> explorePlaceList; // List of nearby places
-        public LatLng[] boundaryCoordinates; // Corners of nearby area
-        public LatLng currentLatLng; // Current location when this places are populated
-        public LatLng searchLatLng; // Search location for finding this places
-        public List<Media> mediaList; // Search location for finding this places
-    }
-}

app/src/main/java/fr/free/nrw/commons/MapController.kt

@@ -0,0 +1,46 @@
+package fr.free.nrw.commons
+
+import fr.free.nrw.commons.location.LatLng
+import fr.free.nrw.commons.nearby.Place
+
+abstract class MapController {
+    /**
+     * We pass this variable as a group of placeList and boundaryCoordinates
+     */
+    inner class NearbyPlacesInfo {
+        @JvmField
+        var placeList: List<Place> = emptyList() // List of nearby places
+
+        @JvmField
+        var boundaryCoordinates: Array<LatLng> = emptyArray() // Corners of nearby area
+
+        @JvmField
+        var currentLatLng: LatLng? = null // Current location when this places are populated
+
+        @JvmField
+        var searchLatLng: LatLng? = null // Search location for finding this places
+
+        @JvmField
+        var mediaList: List<Media>? = null // Search location for finding this places
+    }
+
+    /**
+     * We pass this variable as a group of placeList and boundaryCoordinates
+     */
+    inner class ExplorePlacesInfo {
+        @JvmField
+        var explorePlaceList: List<Place> = emptyList() // List of nearby places
+
+        @JvmField
+        var boundaryCoordinates: Array<LatLng> = emptyArray() // Corners of nearby area
+
+        @JvmField
+        var currentLatLng: LatLng? = null // Current location when this places are populated
+
+        @JvmField
+        var searchLatLng: LatLng? = null // Search location for finding this places
+
+        @JvmField
+        var mediaList: List<Media> = emptyList() // Search location for finding this places
+    }
+}

app/src/main/java/fr/free/nrw/commons/explore/map/ExploreMapCalls.java

@@ -1,8 +1,10 @@
 package fr.free.nrw.commons.explore.map;
 
+import androidx.annotation.NonNull;
 import fr.free.nrw.commons.Media;
 import fr.free.nrw.commons.location.LatLng;
 import fr.free.nrw.commons.media.MediaClient;
+import java.util.Collections;
 import java.util.List;
 import javax.inject.Inject;
 import javax.inject.Singleton;
@@ -23,6 +25,7 @@ public class ExploreMapCalls {
      * @param currentLatLng coordinates of search location
      * @return list of places obtained
      */
+    @NonNull
     List<Media> callCommonsQuery(final LatLng currentLatLng) {
         String coordinates = currentLatLng.getLatitude() + "|" + currentLatLng.getLongitude();
         return mediaClient.getMediaListFromGeoSearch(coordinates).blockingGet();

app/src/main/java/fr/free/nrw/commons/explore/map/ExploreMapPresenter.java

@@ -14,6 +14,7 @@ import fr.free.nrw.commons.explore.map.ExploreMapController.NearbyBaseMarkerThum
 import fr.free.nrw.commons.kvstore.JsonKvStore;
 import fr.free.nrw.commons.location.LatLng;
 import fr.free.nrw.commons.location.LocationServiceManager.LocationChangeType;
+import fr.free.nrw.commons.nearby.Place;
 import io.reactivex.Observable;
 import java.lang.reflect.Proxy;
 import java.util.List;
@@ -182,7 +183,7 @@ public class ExploreMapPresenter
         exploreMapController
             .loadAttractionsFromLocationToBaseMarkerOptions(explorePlacesInfo.currentLatLng,
                 // Curlatlang will be used to calculate distances
-                explorePlacesInfo.explorePlaceList,
+                (List<Place>) explorePlacesInfo.explorePlaceList,
                 exploreMapFragmentView.getContext(),
                 this,
                 explorePlacesInfo);
@@ -230,11 +231,7 @@ public class ExploreMapPresenter
         mylocation.setLongitude(exploreMapFragmentView.getLastMapFocus().getLongitude());
         Float distance = mylocation.distanceTo(dest_location);
 
-        if (distance > 2000.0 * 3 / 4) {
-            return false;
-        } else {
-            return true;
-        }
+        return !(distance > 2000.0 * 3 / 4);
     }
 
 }

app/src/main/java/fr/free/nrw/commons/nearby/NearbyPlaces.java

@@ -1,10 +1,14 @@
 package fr.free.nrw.commons.nearby;
 
+import static java.util.Collections.emptyList;
+
 import android.location.Location;
+import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import fr.free.nrw.commons.nearby.model.NearbyQueryParams;
+import fr.free.nrw.commons.nearby.model.NearbyQueryParams.Radial;
+import fr.free.nrw.commons.nearby.model.NearbyQueryParams.Rectangular;
 import java.io.IOException;
-import java.util.Collections;
 import java.util.List;
 
 import javax.inject.Inject;
@@ -46,13 +50,14 @@ public class NearbyPlaces {
      * @param customQuery
      * @return list of places obtained
      */
+    @NonNull
     List<Place> radiusExpander(final LatLng currentLatLng, final String lang,
         final boolean returnClosestResult, @Nullable final String customQuery) throws Exception {
 
         final int minResults;
         final double maxRadius;
 
-        List<Place> places = Collections.emptyList();
+        List<Place> places = emptyList();
 
         // If returnClosestResult is true, then this means that we are trying to get closest point
         // to use in cardView in Contributions fragment
@@ -113,6 +118,7 @@ public class NearbyPlaces {
      * @return A list of places obtained from the Wikidata query.
      * @throws Exception If an error occurs during the retrieval process.
      */
+    @NonNull
     public List<Place> getFromWikidataQuery(
         final fr.free.nrw.commons.location.LatLng centerPoint,
         final fr.free.nrw.commons.location.LatLng screenTopRight,
@@ -120,11 +126,11 @@ public class NearbyPlaces {
         final boolean shouldQueryForMonuments,
         @Nullable final String customQuery) throws Exception {
         if (customQuery != null) {
-            return okHttpJsonApiClient
-                .getNearbyPlaces(
-                    new NearbyQueryParams.Rectangular(screenTopRight, screenBottomLeft), lang,
+            final List<Place> nearbyPlaces = okHttpJsonApiClient.getNearbyPlaces(
+                    new Rectangular(screenTopRight, screenBottomLeft), lang,
                     shouldQueryForMonuments,
                     customQuery);
+            return nearbyPlaces != null ? nearbyPlaces : emptyList();
         }
 
         final int lowerLimit = 1000, upperLimit = 1500;
@@ -141,9 +147,10 @@ public class NearbyPlaces {
             final int itemCount = okHttpJsonApiClient.getNearbyItemCount(
                 new NearbyQueryParams.Rectangular(screenTopRight, screenBottomLeft));
             if (itemCount < upperLimit) {
-                return okHttpJsonApiClient.getNearbyPlaces(
-                    new NearbyQueryParams.Rectangular(screenTopRight, screenBottomLeft), lang,
+                final List<Place> nearbyPlaces = okHttpJsonApiClient.getNearbyPlaces(
+                    new Rectangular(screenTopRight, screenBottomLeft), lang,
                     shouldQueryForMonuments, null);
+                return nearbyPlaces != null ? nearbyPlaces : emptyList();
             }
         }
 
@@ -175,9 +182,10 @@ public class NearbyPlaces {
                 maxRadius = targetRadius - 1;
             }
         }
-        return okHttpJsonApiClient.getNearbyPlaces(
-            new NearbyQueryParams.Radial(centerPoint, targetRadius / 100f), lang, shouldQueryForMonuments,
+        final List<Place> nearbyPlaces = okHttpJsonApiClient.getNearbyPlaces(
+            new Radial(centerPoint, targetRadius / 100f), lang, shouldQueryForMonuments,
             null);
+        return nearbyPlaces != null ? nearbyPlaces : emptyList();
     }
 
     /**