Fixes #5806 Implemented "Refresh" button to clear the cache and reload the Nearby map (#5891)

* Changed files required to get the app to run correctly. Removed suspend from affected DAO files and funcs, and changed to (Kotlin v1.9.22) and (Kotlin compiler v1.5.8)

* Created refresh button icon, and added it to the nearby_fragment_menu.xml (header of the nearby page). Created function refresh() in NearbyParentFragment.java to handle refresh functionality.

* Replaced refresh() func with emptyCache() and reloadMap()

* Attempt at reloadMap(), no testing done yet.

* added changes for a possibly working emptyCache implementation (needs testing).

* Tested changes as working, edited emptyCache to correctly clear cache and then reload map

---------

Co-authored-by: MarcusBarta <marcusbarta@icloud.com>

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

@@ -41,4 +41,23 @@ public abstract class PlaceDao {
                 saveSynchronous(place);
             });
     }
+
+    /**
+     * Deletes all Place objects from the database.
+     *
+     * @return A Completable that completes once the deletion operation is done.
+     */
+    @Query("DELETE FROM place")
+    public abstract void deleteAllSynchronous();
+
+    /**
+     * Deletes all Place objects from the database.
+     *
+     */
+    public Completable deleteAll() {
+        return Completable
+            .fromAction(() -> {
+                deleteAllSynchronous();
+            });
+    }
 }

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

@@ -35,4 +35,8 @@ public class PlacesLocalDataSource {
     public Completable savePlace(Place place) {
         return placeDao.save(place);
     }
+
+    public Completable clearCache() {
+        return placeDao.deleteAll();
+    }
 }

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

@@ -3,6 +3,7 @@ package fr.free.nrw.commons.nearby;
 import fr.free.nrw.commons.contributions.Contribution;
 import fr.free.nrw.commons.location.LatLng;
 import io.reactivex.Completable;
+import io.reactivex.schedulers.Schedulers;
 import javax.inject.Inject;
 
 /**
@@ -38,4 +39,13 @@ public class PlacesRepository {
         return localDataSource.fetchPlace(entityID);
     }
 
+    /**
+     * Clears the Nearby cache on an IO thread.
+     *
+     * @return A Completable that completes once the cache has been successfully cleared.
+     */
+    public Completable clearCache() {
+        return localDataSource.clearCache()
+            .subscribeOn(Schedulers.io()); // Ensure it runs on IO thread
+    }
 }

app/src/main/java/fr/free/nrw/commons/nearby/fragments/NearbyParentFragment.java

@@ -108,6 +108,7 @@ import fr.free.nrw.commons.utils.NetworkUtils;
 import fr.free.nrw.commons.utils.SystemThemeUtils;
 import fr.free.nrw.commons.utils.ViewUtil;
 import fr.free.nrw.commons.wikidata.WikidataEditListener;
+import io.reactivex.Completable;
 import io.reactivex.Observable;
 import io.reactivex.android.schedulers.AndroidSchedulers;
 import io.reactivex.disposables.Disposable;
@@ -342,9 +343,21 @@ public class NearbyParentFragment extends CommonsDaggerSupportFragment
     public void onCreateOptionsMenu(@NonNull final Menu menu,
         @NonNull final MenuInflater inflater) {
         inflater.inflate(R.menu.nearby_fragment_menu, menu);
+        MenuItem refreshButton = menu.findItem(R.id.item_refresh);
         MenuItem listMenu = menu.findItem(R.id.list_sheet);
         MenuItem saveAsGPXButton = menu.findItem(R.id.list_item_gpx);
         MenuItem saveAsKMLButton = menu.findItem(R.id.list_item_kml);
+        refreshButton.setOnMenuItemClickListener(new OnMenuItemClickListener() {
+            @Override
+            public boolean onMenuItemClick(MenuItem item) {
+                try {
+                    emptyCache();
+                } catch (Exception e) {
+                    throw new RuntimeException(e);
+                }
+                return false;
+            }
+        });
         listMenu.setOnMenuItemClickListener(new OnMenuItemClickListener() {
             @Override
             public boolean onMenuItemClick(MenuItem item) {
@@ -1158,6 +1171,48 @@ public class NearbyParentFragment extends CommonsDaggerSupportFragment
         }
     }
 
+    /**
+     *  Reloads the Nearby map
+     *  Clears all location markers, refreshes them, reinserts them into the map.
+     *
+     */
+    private void reloadMap() {
+        clearAllMarkers(); // Clear the list of markers
+        binding.map.getController().setZoom(ZOOM_LEVEL); // Reset the zoom level
+        binding.map.getController().setCenter(lastMapFocus); // Recenter the focus
+        if (locationPermissionsHelper.checkLocationPermission(getActivity())) {
+            locationPermissionGranted(); // Reload map with user's location
+        } else {
+            startMapWithoutPermission(); // Reload map without user's location
+        }
+        binding.map.invalidate(); // Invalidate the map
+        presenter.updateMapAndList(LOCATION_SIGNIFICANTLY_CHANGED); // Restart the map
+        Timber.d("Reloaded Map Successfully");
+    }
+
+
+    /**
+     * Clears the Nearby local cache and then calls for the map to be reloaded
+     *
+     */
+    private void emptyCache() {
+        // reload the map once the cache is cleared
+        compositeDisposable.add(
+            placesRepository.clearCache()
+                .subscribeOn(Schedulers.io())
+                .observeOn(AndroidSchedulers.mainThread())
+                .andThen(Completable.fromAction(this::reloadMap))
+                .subscribe(
+                    () -> {
+                        Timber.d("Nearby Cache cleared successfully.");
+                    },
+                    throwable -> {
+                        Timber.e(throwable, "Failed to clear the Nearby Cache");
+                    }
+                )
+        );
+    }
+
     private void savePlacesAsKML() {
         final Observable<String> savePlacesObservable = Observable
             .fromCallable(() -> nearbyController