Optimize Nearby labels

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

@@ -4,12 +4,11 @@
 import android.content.res.Resources;
 import android.os.Parcel;
 
+import android.util.SparseArray;
 import androidx.annotation.DrawableRes;
 
 import java.util.Arrays;
-import java.util.HashMap;
 import java.util.List;
-import java.util.Map;
 
 import fr.free.nrw.commons.R;
 
@@ -29,7 +28,6 @@ public enum Label {
     COTTAGE(R.array.cottage_QIDs, R.drawable.round_icon_house),
     FARMHOUSE(R.array.farmhouse_QIDs, R.drawable.round_icon_house),
     TEMPLE(R.array.temple_QIDs, R.drawable.round_icon_church),
-
     CHURCH(R.array.church_QIDs, R.drawable.round_icon_church),
     GAS_STATION(R.array.gas_station_QIDs, R.drawable.round_icon_gas_station),
     RAILWAY_STATION(R.array.railway_station_QIDs, R.drawable.round_icon_railway_station),
@@ -53,9 +51,14 @@ public enum Label {
     UNKNOWN(0, R.drawable.round_icon_unknown);
 
     /**
-     * Lookup map which maps Q-ID -> Label.
+     * Sorted array of Q-ID integers for binary-search lookup.
+     */
+    private static volatile int[] QIDS = new int[0];
+
+    /**
+     * Labels parallel to {@link #QIDS}: QIDS[i] maps to QID_LABELS[i].
      */
-    public static final Map<String, Label> TEXT_TO_DESCRIPTION = new HashMap<>();
+    private static volatile Label[] QID_LABELS = new Label[0];
 
     private final int arrayResId;
     @DrawableRes
@@ -73,21 +76,47 @@ public enum Label {
     }
 
     /**
-     * Loads Q-IDs from Android resources
+     * Loads Q-IDs from Android resources into sorted primitive arrays.
+     * This method is idempotent; subsequent calls after the first are no-ops.
      *
-     * @param context any Android context applicationContext - much safer
+     * @param context any Android context; applicationContext is safest
      */
-    public static void init(final Context context) {
+    public static synchronized void init(final Context context) {
+        if (QIDS.length != 0) {
+            return;
+        }
         final Resources res = context.getResources();
+        // load all values in temp map which will be sorted by default
+        final SparseArray<Label> tempMap = new SparseArray<>();
         for (final Label label : values()) {
             if (label.arrayResId != 0) {
                 final int[] resArray = res.getIntArray(label.arrayResId);
                 for (final int id : resArray) {
-                    final String qid = "Q" + id;
-                    TEXT_TO_DESCRIPTION.put(qid, label);
+                    tempMap.put(id, label);
                 }
             }
         }
+        //separate the ids and labels into arrays for binary search
+        final int[] ids = new int[tempMap.size()];
+        final Label[] labels = new Label[tempMap.size()];
+        for (int i = 0; i < tempMap.size(); i++) {
+            ids[i] = tempMap.keyAt(i);
+            labels[i] = tempMap.valueAt(i);
+        }
+        tempMap.clear();
+        QIDS = ids;
+        QID_LABELS = labels;
+    }
+
+    /**
+     * Looks up a Label by its numeric Q-ID using binary search.
+     *
+     * @param id the integer Q-ID (e.g. 16970)
+     * @return the matching {@link Label}, or {@link Label#UNKNOWN} if not found
+     */
+    public static Label fromQidInt(final int id) {
+        final int pos = Arrays.binarySearch(QIDS, id);
+        return pos >= 0 ? QID_LABELS[pos] : UNKNOWN;
     }
 
     /**
@@ -116,8 +145,10 @@ public static Label fromText(final String text) {
         if ("BOOKMARK".equals(text)) {
             return BOOKMARKS;
         }
-        final Label label = TEXT_TO_DESCRIPTION.get(text);
-        return label == null ? UNKNOWN : label;
+        if (!(text.charAt(0) == 'Q')) {
+            return UNKNOWN;
+        }
+        return fromQidInt(Integer.parseInt(text.substring(1)));
     }
 
     public static List<Label> valuesAsList() {

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

@@ -369,8 +369,7 @@ class NearbyParentFragment : CommonsDaggerSupportFragment(),
         inflater: LayoutInflater, container: ViewGroup?,
         savedInstanceState: Bundle?
     ): View? {
-        if (Label.TEXT_TO_DESCRIPTION.isEmpty())
-            Label.init(requireContext().applicationContext)
+        Label.init(requireContext().applicationContext)
         loadExploreMapData();
 
         binding = FragmentNearbyParentBinding.inflate(inflater, container, false)