Remove the extended page view nonsense

lib/events/photo_opened_event.dart

@@ -1,7 +0,0 @@
-import 'package:photos/models/photo.dart';
-
-class PhotoOpenedEvent {
-  final Photo photo;
-
-  PhotoOpenedEvent(this.photo);
-}

lib/ui/detail_page.dart

@@ -1,11 +1,9 @@
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/material.dart';
 import 'package:like_button/like_button.dart';
-import 'package:photos/core/event_bus.dart';
-import 'package:photos/events/photo_opened_event.dart';
+import 'package:photos/core/cache/image_cache.dart';
 import 'package:photos/favorite_photos_repository.dart';
 import 'package:photos/models/photo.dart';
-import 'package:photos/ui/extents_page_view.dart';
 import 'package:photos/ui/zoomable_image.dart';
 import 'package:photos/utils/date_time_util.dart';
 import 'package:photos/utils/share_util.dart';
@@ -34,12 +32,6 @@ class _DetailPageState extends State<DetailPage> {
     super.initState();
   }
 
-  @override
-  void dispose() {
-    Bus.instance.fire(PhotoOpenedEvent(null));
-    super.dispose();
-  }
-
   @override
   Widget build(BuildContext context) {
     _logger.info("Opening " +
@@ -60,7 +52,7 @@ class _DetailPageState extends State<DetailPage> {
   }
 
   Widget _buildPageView() {
-    return ExtentsPageView.extents(
+    return PageView.builder(
       itemBuilder: (context, index) {
         final photo = _photos[index];
         final image = ZoomableImage(
@@ -71,24 +63,47 @@ class _DetailPageState extends State<DetailPage> {
             });
           },
         );
-        if (index == _selectedIndex) {
-          Bus.instance.fire(PhotoOpenedEvent(photo));
-        }
+        _preloadPhotos(index);
         return image;
       },
-      onPageChanged: (int index) {
+      onPageChanged: (index) {
         _selectedIndex = index;
-        Bus.instance.fire(PhotoOpenedEvent(widget.photos[index]));
+        _preloadPhotos(index);
       },
       physics: _shouldDisableScroll
           ? NeverScrollableScrollPhysics()
           : PageScrollPhysics(),
       controller: PageController(initialPage: _selectedIndex),
       itemCount: _photos.length,
-      extents: 1,
     );
   }
 
+  void _preloadPhotos(int index) {
+    if (index > 0) {
+      _preloadPhoto(_photos[index - 1]);
+    }
+    if (index < _photos.length - 1) {
+      _preloadPhoto(_photos[index + 1]);
+    }
+  }
+
+  void _preloadPhoto(Photo photo) {
+    if (photo.localId == null) {
+      photo.getBytes().then((data) {
+        BytesLruCache.put(photo, data);
+      });
+    } else {
+      final cachedFile = FileLruCache.get(photo);
+      if (cachedFile == null) {
+        photo.getAsset().then((asset) {
+          asset.file.then((file) {
+            FileLruCache.put(photo, file);
+          });
+        });
+      }
+    }
+  }
+
   AppBar _buildAppBar() {
     final actions = List<Widget>();
     if (_photos[_selectedIndex].localId != null) {

lib/ui/gallery.dart

@@ -4,9 +4,8 @@ import 'dart:collection';
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
-import 'package:photos/core/event_bus.dart';
+import 'package:logging/logging.dart';
 import 'package:photos/events/event.dart';
-import 'package:photos/events/photo_opened_event.dart';
 import 'package:photos/models/photo.dart';
 import 'package:photos/ui/detail_page.dart';
 import 'package:photos/ui/loading_widget.dart';
@@ -39,6 +38,7 @@ class Gallery extends StatefulWidget {
 }
 
 class _GalleryState extends State<Gallery> {
+  final Logger _logger = Logger("Gallery");
   final ScrollController _scrollController = ScrollController();
   final List<List<Photo>> _collatedPhotos = List<List<Photo>>();
 
@@ -47,18 +47,10 @@ class _GalleryState extends State<Gallery> {
   Set<Photo> _selectedPhotos = HashSet<Photo>();
   List<Photo> _photos;
   RefreshController _refreshController = RefreshController();
-  StreamSubscription<PhotoOpenedEvent> _photoOpenEventSubscription;
-  Photo _openedPhoto;
 
   @override
   void initState() {
     _requiresLoad = true;
-    _photoOpenEventSubscription =
-        Bus.instance.on<PhotoOpenedEvent>().listen((event) {
-      setState(() {
-        _openedPhoto = event.photo;
-      });
-    });
     if (widget.reloadEvent != null) {
       widget.reloadEvent.listen((event) {
         setState(() {
@@ -69,12 +61,6 @@ class _GalleryState extends State<Gallery> {
     super.initState();
   }
 
-  @override
-  void dispose() {
-    _photoOpenEventSubscription.cancel();
-    super.dispose();
-  }
-
   @override
   Widget build(BuildContext context) {
     if (!_requiresLoad) {
@@ -173,15 +159,6 @@ class _GalleryState extends State<Gallery> {
   }
 
   Widget _buildPhoto(BuildContext context, Photo photo) {
-    Widget thumbnail;
-    if (_openedPhoto == null || _openedPhoto == photo) {
-      thumbnail = Hero(
-        tag: photo.generatedId.toString(),
-        child: ThumbnailWidget(photo),
-      );
-    } else {
-      thumbnail = ThumbnailWidget(photo);
-    }
     return GestureDetector(
       onTap: () {
         if (_selectedPhotos.isNotEmpty) {
@@ -201,7 +178,10 @@ class _GalleryState extends State<Gallery> {
               ? Border.all(width: 4.0, color: Colors.blue)
               : null,
         ),
-        child: thumbnail,
+        child: Hero(
+          tag: photo.generatedId.toString(),
+          child: ThumbnailWidget(photo),
+        ),
       ),
     );
   }