Add hero animation

lib/ui/detail_page.dart

@@ -4,7 +4,6 @@ import 'package:like_button/like_button.dart';
 import 'package:photos/core/cache/lru_map.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/share_util.dart';
 import 'package:logging/logging.dart';
@@ -56,7 +55,7 @@ class _DetailPageState extends State<DetailPage> {
 
   Widget _buildPageView() {
     _pageController = PageController(initialPage: _selectedIndex);
-    return ExtentsPageView.extents(
+    return PageView.builder(
       itemBuilder: (context, index) {
         final photo = _photos[index];
         if (_cachedImages.get(photo.generatedId) != null) {
@@ -73,7 +72,6 @@ class _DetailPageState extends State<DetailPage> {
         _cachedImages.put(photo.generatedId, image);
         return image;
       },
-      extents: 1,
       onPageChanged: (int index) {
         setState(() {
           _selectedIndex = index;

lib/ui/gallery.dart

@@ -40,7 +40,7 @@ class _GalleryState extends State<Gallery> {
       itemCount: _collatedPhotos.length,
       itemBuilder: _buildListItem,
       controller: _scrollController,
-      cacheExtent: 2000,
+      cacheExtent: 1000,
     );
   }
 
@@ -100,7 +100,10 @@ class _GalleryState extends State<Gallery> {
               ? Border.all(width: 4.0, color: Colors.blue)
               : null,
         ),
-        child: ThumbnailWidget(photo),
+        child: Hero(
+          tag: photo.generatedId,
+          child: ThumbnailWidget(photo),
+        ),
       ),
     );
   }

lib/ui/zoomable_image.dart

@@ -1,4 +1,3 @@
-import 'dart:io';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/widgets.dart';
 import 'package:photos/core/cache/image_cache.dart';
@@ -53,6 +52,7 @@ class _ZoomableImageState extends State<ZoomableImage> {
         scaleStateChangedCallback: _scaleStateChangedCallback,
         minScale: PhotoViewComputedScale.contained,
         gaplessPlayback: true,
+        heroAttributes: PhotoViewHeroAttributes(tag: widget.photo.generatedId),
       );
     } else {
       return loadWidget;