Use layer to set download listeners for continuous download

Signed-off-by: Taylor Smock <taylor.smock@kaart.com>

src/main/java/org/openstreetmap/josm/plugins/mapwithai/backend/DownloadListener.java

@@ -62,6 +62,6 @@ public final class DownloadListener implements DataSourceListener, Destroyable {
      * Destroy all download listeners for MapWithAI
      */
     public static void destroyAll() {
-        LISTENERS.forEach(DownloadListener::destroy);
+        new HashSet<>(LISTENERS).forEach(DownloadListener::destroy);
     }
 }

src/main/java/org/openstreetmap/josm/plugins/mapwithai/backend/MapWithAIAction.java

@@ -47,7 +47,6 @@ public class MapWithAIAction extends JosmAction {
                     .collect(Collectors.toList());
             final OsmDataLayer layer = getOsmLayer(osmLayers);
             if ((layer != null) && MapWithAIDataUtils.getMapWithAIData(MapWithAIDataUtils.getLayer(true), layer)) {
-                new DownloadListener(layer.getDataSet());
                 final Notification notification = createMessageDialog();
                 if (notification != null) {
                     notification.show();

src/main/java/org/openstreetmap/josm/plugins/mapwithai/backend/MapWithAILayer.java

@@ -284,6 +284,13 @@ public class MapWithAILayer extends OsmDataLayer implements ActiveLayerChangeLis
         @Override
         public void actionPerformed(ActionEvent e) {
             layer.continuousDownload = !layer.continuousDownload;
+            if (layer.continuousDownload) {
+                for (OsmDataLayer data : MainApplication.getLayerManager().getLayersOfType(OsmDataLayer.class)) {
+                    new DownloadListener(data.getDataSet());
+                }
+            } else {
+                DownloadListener.destroyAll();
+            }
         }
 
         @Override