feat(mobile): image caching & viewer improvements (#4095)

mobile/lib/shared/ui/photo_view/photo_view.dart

@@ -235,6 +235,7 @@ class PhotoView extends StatefulWidget {
   const PhotoView({
     Key? key,
     required this.imageProvider,
+    required this.index,
     this.loadingBuilder,
     this.backgroundDecoration,
     this.wantKeepAlive = false,
@@ -304,6 +305,7 @@ class PhotoView extends StatefulWidget {
         imageProvider = null,
         gaplessPlayback = false,
         loadingBuilder = null,
+        index = 0,
         super(key: key);
 
   /// Given a [imageProvider] it resolves into an zoomable image widget using. It
@@ -419,6 +421,8 @@ class PhotoView extends StatefulWidget {
   /// Useful when you want to drag a widget without restrictions.
   final bool? enablePanAlways;
 
+  final int index;
+
   bool get _isCustomChild {
     return child != null;
   }
@@ -571,6 +575,7 @@ class _PhotoViewState extends State<PhotoView>
                 disableGestures: widget.disableGestures,
                 errorBuilder: widget.errorBuilder,
                 enablePanAlways: widget.enablePanAlways,
+                index: widget.index,
               );
       },
     );
@@ -625,7 +630,7 @@ typedef PhotoViewImageDragStartCallback = Function(
   PhotoViewControllerValue controllerValue,
 );
 
-/// A type definition for a callback when the user drags 
+/// A type definition for a callback when the user drags
 typedef PhotoViewImageDragUpdateCallback = Function(
   BuildContext context,
   DragUpdateDetails details,
@@ -650,4 +655,5 @@ typedef PhotoViewImageScaleEndCallback = Function(
 typedef LoadingBuilder = Widget Function(
   BuildContext context,
   ImageChunkEvent? event,
+  int index,
 );

mobile/lib/shared/ui/photo_view/photo_view_gallery.dart

@@ -281,6 +281,7 @@ class _PhotoViewGalleryState extends State<PhotoViewGallery> {
           )
         : PhotoView(
             key: ObjectKey(index),
+            index: index,
             imageProvider: pageOption.imageProvider,
             loadingBuilder: widget.loadingBuilder,
             backgroundDecoration: widget.backgroundDecoration,
@@ -315,7 +316,10 @@ class _PhotoViewGalleryState extends State<PhotoViewGallery> {
     );
   }
 
-  PhotoViewGalleryPageOptions _buildPageOption(BuildContext context, int index) {
+  PhotoViewGalleryPageOptions _buildPageOption(
+    BuildContext context,
+    int index,
+  ) {
     if (widget._isBuilder) {
       return widget.builder!(context, index);
     }

mobile/lib/shared/ui/photo_view/src/photo_view_wrappers.dart

@@ -35,6 +35,7 @@ class ImageWrapper extends StatefulWidget {
     required this.disableGestures,
     required this.errorBuilder,
     required this.enablePanAlways,
+    required this.index,
   }) : super(key: key);
 
   final ImageProvider imageProvider;
@@ -64,6 +65,7 @@ class ImageWrapper extends StatefulWidget {
   final FilterQuality? filterQuality;
   final bool? disableGestures;
   final bool? enablePanAlways;
+  final int index;
 
   @override
   createState() => _ImageWrapperState();
@@ -128,6 +130,7 @@ class _ImageWrapperState extends State<ImageWrapper> {
         _lastException = null;
         _lastStack = null;
       }
+
       synchronousCall ? setupCB() : setState(setupCB);
     }
 
@@ -212,7 +215,7 @@ class _ImageWrapperState extends State<ImageWrapper> {
 
   Widget _buildLoading(BuildContext context) {
     if (widget.loadingBuilder != null) {
-      return widget.loadingBuilder!(context, _loadingProgress);
+      return widget.loadingBuilder!(context, _loadingProgress, widget.index);
     }
 
     return PhotoViewDefaultLoading(