info: improved location section build

lib/widgets/fullscreen/info/info_page.dart

@@ -80,7 +80,13 @@ class InfoPageState extends State<InfoPage> {
                             children: [
                               Expanded(child: BasicSection(entry: entry)),
                               const SizedBox(width: 8),
-                              Expanded(child: LocationSection(entry: entry, showTitle: false)),
+                              Expanded(
+                                child: LocationSection(
+                                  entry: entry,
+                                  showTitle: false,
+                                  visibleNotifier: widget.visibleNotifier,
+                                ),
+                              ),
                             ],
                           ),
                         ),
@@ -92,7 +98,11 @@ class InfoPageState extends State<InfoPage> {
                           delegate: SliverChildListDelegate(
                             [
                               BasicSection(entry: entry),
-                              LocationSection(entry: entry, showTitle: true),
+                              LocationSection(
+                                entry: entry,
+                                showTitle: true,
+                                visibleNotifier: widget.visibleNotifier,
+                              ),
                             ],
                           ),
                         ),

lib/widgets/fullscreen/info/location_section.dart

@@ -6,29 +6,67 @@ import 'package:flutter/material.dart';
 import 'package:google_maps_flutter/google_maps_flutter.dart';
 import 'package:outline_material_icons/outline_material_icons.dart';
 
-class LocationSection extends AnimatedWidget {
+class LocationSection extends StatefulWidget {
   final ImageEntry entry;
   final bool showTitle;
+  final ValueNotifier<bool> visibleNotifier;
 
-  LocationSection({
+  const LocationSection({
     Key key,
     @required this.entry,
     @required this.showTitle,
-  }) : super(
+    @required this.visibleNotifier,
-            key: key,
+  }) : super(key: key);
-            listenable: Listenable.merge([
+
-              entry.metadataChangeNotifier,
+  @override
-              entry.addressChangeNotifier,
+  _LocationSectionState createState() => _LocationSectionState();
-            ]));
+}
+
+class _LocationSectionState extends State<LocationSection> {
+  String _loadedUri;
+
+  ImageEntry get entry => widget.entry;
+
+  @override
+  void initState() {
+    super.initState();
+    _registerWidget(widget);
+  }
+
+  @override
+  void didUpdateWidget(LocationSection oldWidget) {
+    super.didUpdateWidget(oldWidget);
+    _unregisterWidget(oldWidget);
+    _registerWidget(widget);
+  }
+
+  @override
+  void dispose() {
+    _unregisterWidget(widget);
+    super.dispose();
+  }
+
+  void _registerWidget(LocationSection widget) {
+    entry.metadataChangeNotifier.addListener(_handleChange);
+    entry.addressChangeNotifier.addListener(_handleChange);
+    widget.visibleNotifier.addListener(_handleChange);
+  }
+
+  void _unregisterWidget(LocationSection widget) {
+    entry.metadataChangeNotifier.removeListener(_handleChange);
+    entry.addressChangeNotifier.removeListener(_handleChange);
+    widget.visibleNotifier.removeListener(_handleChange);
+  }
 
   @override
   Widget build(BuildContext context) {
-    return !entry.hasGps
+    final showMap = (_loadedUri == entry.uri) || (entry.hasGps && widget.visibleNotifier.value);
-        ? const SizedBox.shrink()
+    if (showMap) {
-        : Column(
+      _loadedUri = entry.uri;
+      return Column(
         crossAxisAlignment: CrossAxisAlignment.start,
         children: [
-              if (showTitle)
+          if (widget.showTitle)
             const Padding(
               padding: EdgeInsets.only(bottom: 8),
               child: SectionRow('Location'),
@@ -49,9 +87,15 @@ class LocationSection extends AnimatedWidget {
             ),
         ],
       );
+    } else {
+      _loadedUri = null;
+      return const SizedBox.shrink();
     }
   }
 
+  void _handleChange() => setState(() {});
+}
+
 class ImageMap extends StatefulWidget {
   final String markerId;
   final LatLng latLng;

lib/widgets/fullscreen/info/metadata_section.dart

@@ -17,7 +17,7 @@ class MetadataSectionSliver extends StatefulWidget {
   const MetadataSectionSliver({
     @required this.entry,
     @required this.columnCount,
-    this.visibleNotifier,
+    @required this.visibleNotifier,
   });
 
   @override